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Numrering	Referens	Omslagsbild	Hitta
1.	Sörngård, Johanna, et al. (författare) Study of the possibilities with combinations of circularly and linearly polarized light for attosecond delay investigations 2020 Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 53:13 Tidskriftsartikel (refereegranskat)abstract We present calculations on the atomic delay in photoionzation obtained with different combinations of linearly and circularly polarized light, and show how a tensor operator approach can be used to readily obtain results for any combination from a single calculation of the radial integrals. We find that for certain choices of polarization and detection geometry a single time-delay measurement is enough to extract the atomic delay since the relative phase in a RABBIT type measurement will be imprinted on the photo electron anisotropy. We show further that the full angular dependence can be qualitatively understood from a plane wave analysis. The results are illustrated by many-body calculations of two-photon above threshold ionization on argon.
2.	Fink, Reinhold, et al. (författare) Specific production of very long-lived core-excited sulfur atoms by 2p(-1)sigma* excitation of the OCS molecule followed by ultrafast dissociation 2006 Ingår i: Journal of Physics B. - 0953-4075 .- 1361-6455. ; 39:12, s. L269-L275 Tidskriftsartikel (refereegranskat)abstract A core-excited sulfur state with a lifetime almost one order of magnitude longer than in molecular 2p core-hole states is selectively produced by ultrafast dissociation of S 2p -> sigma* excited OCS. Clear evidence for this is provided by strong atomic peaks (20% of the total intensity) in x-ray fluorescence but very weak ones (2%) in the corresponding resonant Auger spectrum. Corroborating the assignment of the spectra, ab initio calculations explain the enhanced lifetime: the Auger decay of the produced D-3(3) (2p(5)3p(5)) sulfur state is strongly decreased as it contradicts a newly derived propensity rule of the L2,3MM Auger decay.
3.	Hartman, Henrik, et al. (författare) The FERRUM project: an extremely long radiative lifetime in Ti II measured in an ion storage ring 2003 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 36, s. 197-202 Tidskriftsartikel (refereegranskat)abstract We have extended the laser probing technique at the CRYRING storage ring to measurement of the extremely long lifetime (28 s) of the metastable 3d2(3P)4s b 4P5/2 level in Ti II. The result obtained demonstrates the power of this method for investigation of such long-lived levels. This is the first experimental lifetime investigation of metastable states in Ti II.
4.	Lundberg, Hans, et al. (författare) Lifetime measurements and transition probabilities in Mo II 2010 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 43 Tidskriftsartikel (refereegranskat)
5.	Bengtsson, Samuel, et al. (författare) Ultrafast control and opto-optical modulation of extreme ultraviolet light 2019 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 52:6 Tidskriftsartikel (refereegranskat)abstract Ultrashort, coherent light pulses in the extreme ultraviolet (XUV) wavelength region are excellent tools for a wide range of experiments. These XUV pulses are in particular used to characterize electron dynamics. Additionally, the high photon energy enables quantum control of short-lived transitions in atoms. These transitions are of interest for ultrafast quantum control as the bandwidth of the control pulses needs to be less than the transition frequency. Coherent XUV pulses would be even more useful if the tools to control and manipulate them existed. Presently, however, no modulators exist for these frequencies, which significantly reduces the number of possible ultrafast optics experiments and applications in the XUV regime. This Ph.D. tutorial addresses this problem and focuses on the control of XUV light in time and space. To enable control of XUV light we have developed a method for opto-optical modulation (OOM), which modulates the phase of XUV light emitted from a gas of atoms. The atoms are resonantly excited with a coherent XUV pulse generated through high order harmonic generation and emit light after the excitation pulse passed. By shifting the resonance frequencies through the AC Stark shift with a non-resonant infrared control pulse, the phase of the emitted light, and therefore its wavefront, is controlled. With OOM the direction of XUV light emitted from noble gases has been controlled, and the temporal dynamics of the emission studied. By varying the delay between the excitation and the control pulse, the time of redirection was controlled, which enabled high signal to noise study of the temporal dynamics of the emission. Furthermore, a proof-of-principle experiment with two control pulses was performed, resulting in a shaped XUV pulse with controlled duration. The technique of OOM presented in this article is still at a very early stage and in order to obtain complete control of the amplitude and phase of the XUV pulses further development is necessary. Such development would present new opportunities for ultrafast XUV quantum control.
6.	Bertolino, Mattias, et al. (författare) Propensity rules and interference effects in laser-Assisted photoionization of helium and neon 2020 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 53:14 Tidskriftsartikel (refereegranskat)abstract We investigate the angle-resolved photoelectron spectra from laser-Assisted photoionization for helium and neon atoms using an ab initio method based on time-dependent surface flux and configuration interaction singles. We find that the shape of the distributions can be interpreted using a propensity rule, an intrinsic difference in the absorption and the emission processes, as well as interference effects between multiple paths to the final angular momentum state. The difference between absorption and emission is hidden in the first sideband in neon due to the multiple competing m channels, while in the second sideband a qualitative difference between absorption and emission is observed. In the m-resolved case, a clear difference is observed already in the first sideband, as exemplified in helium and m-resolved neon.
7.	Bruder, Lukas, et al. (författare) Coherent multidimensional spectroscopy in the gas phase 2019 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 52:18 Tidskriftsartikel (refereegranskat)abstract Recent work applying multidimentional coherent electronic spectroscopy at dilute samples in the gas phase is reviewed. The development of refined phase cycling approaches with improved sensitivity has opened up new opportunities to probe even dilute gas-phase samples. In this context, first results of two-dimensional spectroscopy performed at doped helium droplets reveal the femtosecond dynamics upon the electronic excitation of cold, weakly-bound molecules, and even the induced dynamics from the interaction with the helium environment. Such experiments, offering well-defined conditions at low temperatures, are potentially enabling the isolation of fundamental processes in the excitation and charge transfer dynamics of molecular structures which so far have been masked in complex bulk environments.
8.	Busto, D., et al. (författare) Time-frequency representation of autoionization dynamics in helium 2018 Ingår i: Journal of Physics B-Atomic Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 51:4 Tidskriftsartikel (refereegranskat)abstract Autoionization, which results from the interference between direct photoionization and photoexcitation to a discrete state decaying to the continuum by configuration interaction, is a well known example of the important role of electron correlation in light-matter interaction. Information on this process can be obtained by studying the spectral, or equivalently, temporal complex amplitude of the ionized electron wave packet. Using an energy-resolved interferometric technique, we measure the spectral amplitude and phase of autoionized wave packets emitted via the sp2+ and sp3(+) resonances in helium. These measurements allow us to reconstruct the corresponding temporal profiles by Fourier transform. In addition, applying various time-frequency representations, we observe the build-up of the wave packets in the continuum, monitor the instantaneous frequencies emitted at any time and disentangle the dynamics of the direct and resonant ionization channels.
9.	Carlström, Stefanos, et al. (författare) Quantum coherence in photo-ionisation with tailored XUV pulses 2018 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 51:1 Tidskriftsartikel (refereegranskat)abstract Ionisation with ultrashort pulses in the extreme ultraviolet (XUV) regime can be used to prepare an ion in a superposition of spin-orbit substates. In this work, we study the coherence properties of such a superposition, created by ionising xenon atoms using two phase-locked XUV pulses at different frequencies. In general, if the duration of the driving pulse exceeds the quantum beat period, dephasing will occur. If however, the frequency difference of the two pulses matches the spin-orbit splitting, the coherence can be efficiently increased and dephasing does not occur.
10.	Cheng, Yu Chen, et al. (författare) Imaging multiphoton ionization dynamics of CH3I at a high repetition rate XUV free-electron laser 2021 Ingår i: Journal of Physics B-Atomic Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 54:1 Tidskriftsartikel (refereegranskat)abstract XUV multiphoton ionization of molecules is commonly used in free-electron laser experiments to study charge transfer dynamics. However, molecular dissociation and electron dynamics, such as multiple photon absorption, Auger decay, and charge transfer, often happen on competing time scales, and the contributions of individual processes can be difficult to unravel. We experimentally investigate the Coulomb explosion dynamics of methyl iodide upon core-hole ionization of the shallow inner-shell of iodine (4d) and classically simulate the fragmentation by phenomenologically introducing ionization dynamics and charge transfer. Under our experimental conditions with medium fluence and relatively long XUV pulses (similar to 75 fs), we find that fast Auger decay prior to charge transfer significantly contributes to the charging mechanism, leading to a yield enhancement of higher carbon charge states upon molecular dissociation. Furthermore, we argue for the existence of another charging mechanism for the weak fragmentation channels leading to triply charged carbon atoms. This study shows that classical simulations can be a useful tool to guide the quantum mechanical description of the femtosecond dynamics upon multiphoton absorption in molecular systems.
11.	Ekholm, V., et al. (författare) Core-hole localization and ultra-fast dissociation in SF6 2020 Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 53:18 Tidskriftsartikel (refereegranskat)abstract Resonant inelastic x-ray scattering spectra excited at the fluorine K resonances of SF(6)have been recorded. While a small but significant propensity for electronically parity-allowed transitions is found, the observation of parity-forbidden electronic transitions is attributed to vibronic coupling that breaks the global inversion symmetry of the electronic wavefunction and localizes the core hole. The dependence of the scattering cross section on the polarization of the incident radiation and the scattering angle is interpreted in terms of local pi/sigma symmetry around the S-F bond. This symmetry selectivity prevails during the dissociation that occurs during the scattering process.
12.	Eriksson, G., et al. (författare) Finite-size effects in the dynamics of few bosons in a ring potential 2018 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 51:3 Tidskriftsartikel (refereegranskat)abstract We study the temporal evolution of a small number N of ultra-cold bosonic atoms confined in a ring potential. Assuming that initially the system is in a solitary-wave solution of the corresponding mean-field problem, we identify significant differences in the time evolution of the density distribution of the atoms when it instead is evaluated with the many-body Schrödinger equation. Three characteristic timescales are derived: the first is the period of rotation of the wave around the ring, the second is associated with a 'decay' of the density variation, and the third is associated with periodic 'collapses' and 'revivals' of the density variations, with a factor of separating each of them. The last two timescales tend to infinity in the appropriate limit of large N, in agreement with the mean-field approximation. These findings are based on the assumption of the initial state being a mean-field state. We confirm this behavior by comparison to the exact solutions for a few-body system stirred by an external potential. We find that the exact solutions of the driven system exhibit similar dynamical features.
13.	Forbes, Ruaridh, et al. (författare) Time-resolved site-selective imaging of predissociation and charge transfer dynamics : The CH3I B-band 2020 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 53:22 Tidskriftsartikel (refereegranskat)abstract The predissociation dynamics of the 6s (B2E) Rydberg state of gas-phase CH3I were investigated by time-resolved Coulomb-explosion imaging using extreme ultraviolet (XUV) free-electron laser pulses. Inner-shell ionization at the iodine 4d edge was utilized to provide a site-specific probe of the ensuing dynamics. The combination of a velocity-map imaging (VMI) spectrometer coupled with the pixel imaging mass spectrometry (PImMS) camera permitted three-dimensional ionic fragment momenta to be recorded simultaneously for a wide range of iodine charge states. In accord with previous studies, initial excitation at 201.2 nm results in internal conversion and subsequent dissociation on the lower-lying A-state surface on a picosecond time scale. Examination of the time-dependent yield of low kinetic energy iodine fragments yields mechanistic insights into the predissociation and subsequent charge transfer following multiple ionization of the iodine products. The effect of charge transfer was observed through differing delay-dependencies of the various iodine charge states, from which critical internuclear distances for charge transfer could be inferred and compared to a classical over-the-barrier model. Time-dependent photofragment angular anisotropy parameters were extracted from the central slice of the Newton sphere, without Abel inversion, and highlight the effect of rotation of the parent molecule before dissociation, as observed in previous
14.	Guo, Chen, et al. (författare) Phase control of attosecond pulses in a train 2018 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 51:3 Tidskriftsartikel (refereegranskat)abstract Ultrafast processes in matter can be captured and even controlled by using sequences of few-cycle optical pulses, which need to be well characterized, both in amplitude and phase. The same degree of control has not yet been achieved for few-cycle extreme ultraviolet pulses generated by high-order harmonic generation (HHG) in gases, with duration in the attosecond range. Here, we show that by varying the spectral phase and carrier-envelope phase (CEP) of a high-repetition rate laser, using dispersion in glass, we achieve a high degree of control of the relative phase and CEP between consecutive attosecond pulses. The experimental results are supported by a detailed theoretical analysis based upon the semi-classical three-step model for HHG.
15.	Kiselev, M. D., et al. (författare) An experimental and theoretical study of the Kr 3d correlation satellites 2022 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 55:5 Tidskriftsartikel (refereegranskat)abstract The Kr 3d correlation satellites have been studied experimentally by using plane polarized synchrotron radiation to record polarization dependent photoelectron spectra (PES), and theoretically by employing the R-matrix method to calculate photoionization cross sections, PES and angular distributions. The experimental spectra have allowed the photoelectron anisotropy parameters characterizing the angular distributions, and the intensity branching ratios, related to the photoionization partial cross sections, to be evaluated. The results are discussed in terms of normal and conjugate shake-up processes. The experimental and calculated photoelectron angular distributions associated with those correlation satellites that arise predominantly through conjugate shake-up mechanisms are shown to be isotropic. In contrast, the anisotropy parameters associated with satellites due to normal shake-up processes exhibit a dependence on electron kinetic energy similar to that of the anisotropy parameters corresponding to the Kr 3d main lines. The theoretical results include an analysis of the partial waves representing the emitted photoelectron and, for certain correlation satellites, show that a particular ionization continuum dominates. This, in turn, may allow the dominant normal or conjugate shake-up mechanism forming the satellite to be identified.
16.	Kockert, Hansjochen, et al. (författare) UV-induced dissociation of CH2BrI probed by intense femtosecond XUV pulses 2022 Ingår i: JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 55:1 Tidskriftsartikel (refereegranskat)abstract The ultraviolet (UV)-induced dissociation and photofragmentation of gas-phase CH2BrI molecules induced by intense femtosecond extreme ultraviolet (XUV) pulses at three different photon energies are studied by multi-mass ion imaging. Using a UV-pump-XUV-probe scheme, charge transfer between highly charged iodine ions and neutral CH2Br radicals produced by C-I bond cleavage is investigated. In earlier charge-transfer studies, the center of mass of the molecules was located along the axis of the bond cleaved by the pump pulse. In the present case of CH2BrI, this is not the case, thus inducing a rotation of the fragment. We discuss the influence of the rotation on the charge transfer process using a classical over-the-barrier model. Our modeling suggests that, despite the fact that the dissociation is slower due to the rotational excitation, the critical interatomic distance for charge transfer is reached faster. Furthermore, we suggest that charge transfer during molecular fragmentation may be modulated in a complex way.
17.	Kovács, K, et al. (författare) Multi-parameter optimization of a loose focusing high flux high-harmonic beamline 2019 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 52:5, s. 055402-055402 Tidskriftsartikel (refereegranskat)abstract We perform a multi-dimensional parameter scan in the generation of high-order harmonics, with the main purpose to find the macroscopic conditions that optimize the harmonic yield in a specific spectral domain, around 40 eV for this particular case. The scanned parameters are the laser pulse energy, gas pressure, interaction cell position relative to focus and the cell length, while the fixed parameters are chosen to model a loose focusing configuration which is used in many existing laboratories. We performed the simulations with a 3D non-adiabatic model complemented by a detailed analysis of the phase matching mechanisms involved in an efficient harmonic generation. Based on the results we identify a range of parameter combinations that lead to a high yield in the specified spectral domain. The method and results presented here can be the framework for the design and construction of high flux high-order harmonic generation beamlines.
18.	Kühn, Sergei, et al. (författare) The ELI-ALPS facility : The next generation of attosecond sources 2017 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 50:13 Forskningsöversikt (refereegranskat)abstract This review presents the technological infrastructure that will be available at the Extreme Light Infrastructure Attosecond Light Pulse Source (ELI-ALPS) international facility. ELI-ALPS will offer to the international scientific community ultrashort pulses in the femtosecond and attosecond domain for time-resolved investigations with unprecedented levels of high quality characteristics. The laser sources and the attosecond beamlines available at the facility will make attosecond technology accessible for scientists lacking access to these novel tools. Time-resolved investigation of systems of increasing complexity is envisaged using the end stations that will be provided at the facility.
19.	L'Huillier, Anne (författare) Multiple harmonic conversion of 1064 nm in rare gases 2017 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 50:6 Forskningsöversikt (refereegranskat)
20.	Olofsson, Edvin, et al. (författare) Frustrated tunneling dynamics in ultrashort laser pulses 2021 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 54:15 Tidskriftsartikel (refereegranskat)abstract We study a model for frustrated tunneling ionization using ultrashort laser pulses. The model is based on the strong field approximation and it employs the saddle point approximation to predict quasiclassical trajectories that are captured on Rydberg states. We present a classification of the saddle-point solutions and explore their behavior as functions of angular momentum of the final state, as well as the carrier-envelope phase (CEP) of the laser pulse. We compare the final state population computed by the model to results obtained by numerical propagation of the time-dependent Schrödinger equation (TDSE) for the hydrogen atom. While we find qualitative agreement in the CEP dependence of the populations in principal quantum numbers, n, the populations to individual angular momentum channels, ℓ, are found to be inconsistent between model and TDSE. Thus, our results show that improvements of the quasiclassical trajectories are in order for a quantitative model of frustrated tunneling ionization.
21.	Rontani, Massimo, et al. (författare) On the renormalization of contact interactions for the configuration-interaction method in two-dimensions 2017 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 50:6 Tidskriftsartikel (refereegranskat)abstract The configuration interaction (CI) method for calculating the exact eigenstates of a quantum-mechanical few-body system is problematic when applied to particles interacting through contact forces. In dimensions higher than one the approach fails due to the pathology of the Dirac δ-potential, making it impossible to reach convergence by gradually increasing the size of the Hilbert space. However, this problem may be cured in a rather simple manner by renormalizing the strength of the contact potential when diagonalizing in a truncated Hilbert space. One hereby relies on the comparison of the CI results to the two-body ground-state energy obtained by the exact solution of the Schrödinger equation for a regularized contact interaction. We discuss here a scheme that provides cutoff-independent few-body physical observables. The method is applied to a few-body system of ultracold atoms confined by a two-dimensional harmonic oscillator.
22.	Si, Ran, et al. (författare) Proposal for observation of transitions induced by external magnetic fields mixing in the lower states : with an example from Fe X 2020 Ingår i: Journal of Physics B. - : Institute of Physics (IOP). - 0953-4075 .- 1361-6455. ; 53:9 Tidskriftsartikel (refereegranskat)abstract It is normally assumed that induced transitions, by e.g. hyperfine, magnetic field or spin interaction, arise due to mixing in the upper levels. In this paper we discuss an example when mixing in the lower levels through an externally applied magnetic field gives rise to a magnetic field induced transition. We discuss the theory for such a transition and give an example from Fe X, which is relevant for the determination of the magnetic field of the solar corona. To make this possible, it is important to determine the energy difference between the 3p(4)3d D-4(5/2) and D-4(7/2), which are accidentally very close in energy in Fe X. The splitting of these levels is expected to be around 3.5 cm(-1) whereas their excitation energies are about 388 709 cm(-1). We discuss how this fine structure can be determined, by observing transitions from levels that decay into this pair which have a longer wavelength than the resonance transition. Finally we discuss an experimental scenario based on an electron beam ion trap and a Fabry-Perot interferometer, to perform the measurement of this interval.
23.	Sorensen, S. L., et al. (författare) From synchrotrons for XFELs : The soft x-ray near-edge spectrum of the ESCA molecule 2020 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 53:24 Tidskriftsartikel (refereegranskat)abstract A predictive understanding of soft x-ray near-edge absorption spectra of small molecules is an enduring theoretical challenge and of current interest for x-ray probes of molecular dynamics. We report the experimental absorption spectrum for the electron spectroscopy for chemical analysis (ESCA) molecule (ethyl trifluoroacetate) near the carbon 1s absorption edge between 285-300 eV. The ESCA molecule with four chemically distinct carbon sites has previously served as a theoretical benchmark for photoelectron spectra and now for photoabsorption spectra. We report a simple edge-specific approach for systematically expanding standard basis sets to properly describe diffuse Rydberg orbitals and the importance of triple excitations in equation-of-motion coupled-cluster calculations of the energy interval between valence and Rydberg excitations.
24.	Su, Yangluojia, et al. (författare) The structure and radiative lifetimes of negative ions homologous to N- 2019 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 52:12, s. 1-11 Tidskriftsartikel (refereegranskat)abstract Negative ions homologous to N- are interesting systems, since there are several bound terms within the ground configuration. The forbidden transitions between them, often dominated by the magnetic dipole contributions, are affected by term mixing - a relativistic effect. When increasing the nuclear charge in the homologous sequence of negative ions, this effect increases. In this paper we use systematic multiconfiguration Dirac-Hartree-Fock calculations to study these effects and predict affinities, level splittings and transition rates between bound states of N-, P-, As-, Sb- and Bi-. By monitoring the line strengths we are able to predict the deviation from the non-relativistic LS-coupled values for transitions between levels of the lowest 3P term. For Sb- the 1D term is also bound, and the prediction for the rates of its transition to the 3P-levels is a challenge for theory. For Bi- less is known experimentally and we analyze its structure and the relativistic contributions to it.
25.	Turconi, M., et al. (författare) Spin-orbit-resolved spectral phase measurements around a Fano resonance 2020 Ingår i: Journal of Physics B-Atomic Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 53:18 Tidskriftsartikel (refereegranskat)abstract We apply a spectrally-resolved electron interferometry technique to the measurement of the spectral phase in the vicinity of the 3s(1)3p(6)4p Fano resonance of argon. We show that it allows disentangling the phases of the two nearly-overlapping electron wavepackets corresponding to different spin-orbit final states. Using simple assumptions, it is possible to process the experimental data and numerically isolate each component in a self-consistent manner. This in turn allows reconstructing the autoionization dynamics of the dominant channel.
26.	Young, Linda, et al. (författare) Roadmap of ultrafast x-ray atomic and molecular physics 2018 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 51:3 Forskningsöversikt (refereegranskat)abstract X-ray free-electron lasers (XFELs) and table-top sources of x-rays based upon high harmonic generation (HHG) have revolutionized the field of ultrafast x-ray atomic and molecular physics, largely due to an explosive growth in capabilities in the past decade. XFELs now provide unprecedented intensity (1020 W cm-2) of x-rays at wavelengths down to ∼1 Ångstrom, and HHG provides unprecedented time resolution (∼50 attoseconds) and a correspondingly large coherent bandwidth at longer wavelengths. For context, timescales can be referenced to the Bohr orbital period in hydrogen atom of 150 attoseconds and the hydrogen-molecule vibrational period of 8 femtoseconds; wavelength scales can be referenced to the chemically significant carbon K-edge at a photon energy of ∼280 eV (44 Ångstroms) and the bond length in methane of ∼1 Ångstrom. With these modern x-ray sources one now has the ability to focus on individual atoms, even when embedded in a complex molecule, and view electronic and nuclear motion on their intrinsic scales (attoseconds and Ångstroms). These sources have enabled coherent diffractive imaging, where one can image non-crystalline objects in three dimensions on ultrafast timescales, potentially with atomic resolution. The unprecedented intensity available with XFELs has opened new fields of multiphoton and nonlinear x-ray physics where behavior of matter under extreme conditions can be explored. The unprecedented time resolution and pulse synchronization provided by HHG sources has kindled fundamental investigations of time delays in photoionization, charge migration in molecules, and dynamics near conical intersections that are foundational to AMO physics and chemistry. This roadmap coincides with the year when three new XFEL facilities, operating at Ångstrom wavelengths, opened for users (European XFEL, Swiss-FEL and PAL-FEL in Korea) almost doubling the present worldwide number of XFELs, and documents the remarkable progress in HHG capabilities since its discovery roughly 30 years ago, showcasing experiments in AMO physics and other applications. Here we capture the perspectives of 17 leading groups and organize the contributions into four categories: ultrafast molecular dynamics, multidimensional x-ray spectroscopies; high-intensity x-ray phenomena; attosecond x-ray science.
27.	Grumer, Jon, et al. (författare) Hyperfine induced intensity redistribution in In II 2010 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 43:7 Tidskriftsartikel (refereegranskat)abstract We present a theoretical investigation of the hyperfine structure of the 5s5d D-3(2)-5s4f F-3(2,3)0 transitions in In II. Earlier work has failed in determining hyperfine constants for the upper levels of these transitions. We show that this is due to strong off-diagonal hyperfine interaction, which not only changes the position of the individual hyperfine lines but also introduces large intensity redistributions among the different hyperfine levels. We present hyperfine dependent gf-values and show that off-diagonal hyperfine interaction reduces some of the gf-values by two orders of magnitude, while others are increased by up to more than a factor of 6. We also discuss the influence on the hyperfine structure of an accurate representation of the level-splitting of the 5s4f configuration. We show that the hyperfine interaction in F-3(3)0 and F-1(3)0 is very hard to determine accurately even in a large-scale calculation, and we derive a semi-empirical method for adjusting our results using an experimentally known, diagonal hyperfine constant for 5s4f F-1(3)0. The resulting theoretical synthetic spectra reproduce the experimental values to high accuracy and facilitate the identification of all observed lines.
28.	Öhrwall, Gunnar, et al. (författare) Photofragmentation of cyanogen upon carbon and nitrogen K-shell excitation by partial ion yield experiments 2010 Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 43:9, s. 095201- Tidskriftsartikel (refereegranskat)abstract Partial ion yield spectroscopy was used to study fragmentation processes in cyanogen after C 1s and N 1s photoexcitation. The interpretation of the core excitation spectrum mostly follows the literature, but the high resolution has in some cases allowed a more detailed assignment. Using the fact that in Rydberg states there is an intensity increase as the fragmentation process becomes more extensive compared to valence orbitals, we have been able to distinguish resonances with valence and Rydberg character. Furthermore, we have been able to assign features in the ionization continuum as arising from double excitations or shape resonances, by observation of the suppression of anion yield at shape resonances.
29.	Aumayr, Friedrich, et al. (författare) Roadmap on photonic, electronic and atomic collision physics : III. Heavy particles 2019 Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 52:17 Tidskriftsartikel (refereegranskat)abstract We publish three Roadmaps on photonic, electronic and atomic collision physics in order to celebrate the 60th anniversary of the ICPEAC conference. Roadmap III focusses on heavy particles: with zero to relativistic speeds. Modern theoretical and experimental approaches provide detailed insight into the wide range of many-body interactions involving projectiles and targets of varying complexity ranging from simple atoms, through molecules and clusters, complex biomolecules and nanoparticles to surfaces and crystals. These developments have been driven by technological progress and future developments will expand the horizon of the systems that can be studied. This Roadmap aims at looking back along the road, explaining the evolution of the field, and looking forward, collecting nineteen contributions from leading scientists in the field.
30.	Ingle, R. A., et al. (författare) Carbon K-edge x-ray emission spectroscopy of gas phase ethylenic molecules 2022 Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 55:4 Tidskriftsartikel (refereegranskat)abstract We report on the C K-edge x-ray absorption spectra and the resonant (RXES) and non-resonant (NXES) x-ray emission spectra of ethylene, allene and butadiene in the gas phase. The RXES and NXES show clear differences for the different molecules. Overall both types of spectra are more structured for ethylene and allene, than for butadiene. Using density functional theory–restricted open shell configuration interaction single calculations, we simulate the spectra with remarkable agreement with the experiment. We identify the spectral features as being due to transitions involving localised 1s orbitals. For allene, there are distinct spectral bands that reflect transitions predominantly from either the central or terminal carbon atoms. These results are discussed in the context of ultrafast x-ray studies aimed at detecting the passage through conical intersections in polyatomic molecules.
31.	Lynga, C, et al. (författare) High-order harmonic generation in molecular gases 1996 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 29:14, s. 3293-3302 Tidskriftsartikel (refereegranskat)abstract We present an experimental study of harmonic generation in molecular gases, using the fundamental (800 nm) and the second harmonic (400 nm) of a 150 fs titanium - sapphire laser at an intensity of ##IMG## [http://ej.iop.org/images/0953-4075/29/14/032/img1.gif] . We compare the conversion efficiency and the maximum energy obtained in different species: rare gases (Ar, Xe), diatomic molecules ( ##IMG## [http://ej.iop.org/images/0953-4075/29/14/032/img2.gif] , ##IMG## [http://ej.iop.org/images/0953-4075/29/14/032/img3.gif] , ##IMG## [http://ej.iop.org/images/0953-4075/29/14/032/img4.gif] , CO) and polyatomic molecules ( ##IMG## [http://ej.iop.org/images/0953-4075/29/14/032/img5.gif] , ##IMG## [http://ej.iop.org/images/0953-4075/29/14/032/img2.gif] O, ##IMG## [http://ej.iop.org/images/0953-4075/29/14/032/img7.gif] , ##IMG## [http://ej.iop.org/images/0953-4075/29/14/032/img8.gif] , ##IMG## [http://ej.iop.org/images/0953-4075/29/14/032/img9.gif] ). The harmonic spectra from molecular gases are very similar to those obtained in the atomic gases, with a plateau and a cutoff whose location is strongly correlated to the value of the ionization potential. The conversion efficiency is not higher than that of the rare gases.
32.	Darby-Lewis, D., et al. (författare) Synthetic spectra of BeH, BeD and BeT for emission modeling in JET plasmas 2018 Ingår i: Journal of Physics B. - : IOP PUBLISHING LTD. - 0953-4075 .- 1361-6455. ; 51:18 Tidskriftsartikel (refereegranskat)abstract A theoretical model for isotopologues of beryllium monohydride, BeH, BeD and BeT, A (2)Pi to X (2)Sigma(+) visible and X (2)Sigma(+) to X (2)Sigma(+) infrared rovibronic spectra is presented. The MARVEL procedure is used to compute empirical rovibronic energy levels for BeH, BeD and BeT, using experimental transition data for the X (2)Sigma(+), A (2)Pi, and C (2)Sigma(+) states. The energy levels from these calculations are then used in the program Duo to produce a potential energy curve for the ground state, X (2)Sigma, and to fit an improved potential energy curve for the first excited state, A (2)Pi, including a spin-orbit coupling term, a A-doubling state to state (A-X states) coupling term, and Born-Oppenheimer breakdown terms for both curves. These, along with a previously computed ab initio dipole curve for the X and A states are used to generate vibrational-rotational wavefunctions, transition energies and A-values. From the transition energies and Einstein coefficients, accurate assigned synthetic spectra for BeH and its isotopologues are obtained at given rotational and vibrational temperatures. The BeH spectrum is compared with a high resolution hollow-cathode lamp spectrum and the BeD spectrum with high resolution spectra from JET giving effective vibrational and rotational temperatures. Full A-X and X-X line lists are given for BeH, BeD and BeT and provided as supplementary data on the ExoMol website.
33.	Lawson, K. D., et al. (författare) Population modelling of the He II energy levels in tokamak plasmas : I. Collisional excitation model 2019 Ingår i: Journal of Physics B. - : Institute of Physics (IOP). - 0953-4075 .- 1361-6455. ; 52:4 Tidskriftsartikel (refereegranskat)abstract Helium is widely used as a fuel or minority gas in laboratory fusion experiments, and will be present as ash in DT thermonuclear plasmas. It is therefore essential to have a good understanding of its atomic physics. To this end He II population modelling has been undertaken for the spectroscopic levels arising from shells with principal quantum number n = 1-5. This paper focuses on a collisional excitation model; ionisation and recombination will be considered in a subsequent article. Heavy particle collisional excitation rate coefficients have been generated to supplement the currently-available atomic data for He II, and are presented for proton, deuteron, triton and alpha-particle projectiles. The widely-used criterion for levels within an n shell being populated in proportion to their statistical weights is reassessed with the most recent atomic data, and found not to apply to the He II levels at tokamak densities (10(18)-10(21) m(-3)). Consequences of this and other likely sources of errors are quantified, as is the effect of differing electron and ion temperatures. Line intensity ratios, including the so-called 'branching ratios' and the fine-structure beta(1), beta(2), beta(3), and gamma ratios, are discussed, the latter with regard to their possible use as diagnostics.
34.	Adenier, Guillaume, et al. (författare) Is the fair sampling assumption supported by EPR experiments? 2007 Ingår i: Journal of Physics B: At. Mol. Opt. Phys.. - : Institute of Physics ( IOP ), Bristol. - 0953-4075 .- 1361-6455. ; 40:1, s. 131-141 Tidskriftsartikel (refereegranskat)abstract We analyse optical EPR experimental data performed by Weihs et al in Innsbruck 1997–1998. We show that for some linear combinations of the raw coincidence rates, the experimental results display some anomalous behaviour that a more general source state (like non-maximally entangled state) cannot straightforwardly account for. We attempt to explain these anomalies by taking account of the relative efficiencies of the four channels. For this purpose, we use the fair sampling assumption, and assume explicitly that the detection efficiencies for the pairs of entangled photons can be written as a product of the two corresponding detection efficiencies for the single photons. We show that this explicit use of fair sampling cannot be maintained to be a reasonable assumption as it leads to an apparent violation of the no-signalling principle.
35.	Alvarez Ruiz, Jesus, et al. (författare) Synchrotron radiation induced fluorescence spectroscopy of SF6 2005 Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 38, s. 387- Tidskriftsartikel (refereegranskat)abstract The fluorescence of gaseous SF6 was investigated after excitation with 25-80eV synchrotron radiation photons. The total UV-Vis-near IR fluorescence yield was recorded and interpreted in terms of inner valence excitations/ionizations and double excitations in SF6. Dispersed fluorescence measurements in the 400-1000 nm spectral range reveal excited S, S+, F and F+ fragments as solely responsible for the emission. The fluorescence intensity of some of the observed atomic transitions was monitored as a function of the excitation energy. Single, double and triple excitations as well as direct ionizations and shake-ups are proposed as the triggering processes responsible for the creation of the emitting fragments.
36.	Andersson, Martin, et al. (författare) Effects on intercombination transition rates and branching ratios - the UV0.01 (3s(2)3p(2) P-3(1,2)-3s3p(3 5)S(2)) multiplet in SiI-like ions revisited 2007 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 40:4, s. 709-726 Tidskriftsartikel (refereegranskat)abstract We report on large-scale ab initio calculations for intercombination lines in Si I-like ions. Two measurable quantities, the lifetime of the 3s3p(3 5)S(2) level and the branching ratio of the two lines are discussed, to infer the importance of different features of our calculations. The effects of core polarization, two-body spin-dependent operators and Dirac contra Breit-Pauli approaches are discussed. Earlier calculations are reviewed and evaluated. The calculated lifetimes are in good agreement with experiments, while a discrepancy persists for branching ratios.
37.	Andersson, Martin, et al. (författare) Hyperfine dependent lifetimes in Mg-like ions 2010 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 43:9 Tidskriftsartikel (refereegranskat)abstract Theoretical investigations of the hyperfine quenching of the two metastable levels 1s(2)2s(2)2p(6)3s3p P-3(0) and P-3(2) have been performed along the magnesium-like iso-electronic sequence ranging from Z = 12 to Z = 31. It is shown that the lifetime of the latter level is sensitive to hyperfine quenching in the beginning of the sequence, but that this sensitivity decreases going to higher Z. It is also shown that the branching fractions of the 3s(2) S-1(0)-3s3p P-3(2) and 3s3p P-3(1)-3s3p P-3(2) transitions are very sensitive to hyperfine quenching, which could lead to some dramatic effects in the spectrum. Our predicted transition rates of the hyperfine induced 3s(2) S-1(0)-3s3p P-3(0) transition are compared to earlier results and some disagreements are found and explained. The present predicted lifetime of 3s3p P-3(0) in Al-27(+) is slightly longer than the recent measurement, but in better agreement than earlier predictions.
38.	Andersson, Martin, et al. (författare) Hyperfine induced interference effects in the 4s4d D-3(2)-4s4f F-3(2,3) transitions in GaII 2006 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 39:20, s. 4239-4247 Tidskriftsartikel (refereegranskat)abstract We report relativistic multiconfiguration Dirac-Hartree-Fock calculations of transitions between the hyperfine levels of 4s4f F-3(2,3) and 4s4d D-3(2) in Ga II. The capacity of two newly developed programs connected to the grasp VU package for generating synthetic spectra is explored. The obtained theoretical spectra are compared to Fourier transform spectra and good agreement is found. The importance of hyperfine induced interference effects for the 4s4d D-3(2)-4s4f F-3(2) transitions is pointed out, and the gf values for all the hyperfine transitions are given.
39.	Andersson, Martin, et al. (författare) Systematic studies of highly excited Rydberg states in ions with two valance electrons 2006 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 39:12, s. 2815-2826 Tidskriftsartikel (refereegranskat)abstract A method, based on the multiconfiguration Hartree-Fock approach, for ab initio calculations of Rydberg states has been developed. The method has been tested for a number of highly excited Rydberg states, with quantum numbers l = 4 - 8 and n <= 9, in Mg-like and Be-like ions. The results are compared with Hartree-Fock calculations to investigate the influence of correlation and, to a lesser extent, relativistic effects. The theoretical spectra for Cl VI and the lifetimes of the 2s6g-levels in O V are in excellent agreement with experimental results. More limited calculations have also been done for some Rydberg series in S V and Ar VII to illustrate the changing influence of perturbers along the isoelectronic sequence. The difficulties of using isoelectronic extrapolation/interpolation in making predictions for this kind of systems are discussed.
40.	Andersson, Martin, et al. (författare) The anomalous hyperfine structure of Al II 2012 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 45:13 Tidskriftsartikel (refereegranskat)abstract The hyperfine structure of a large number of transitions in Al II cannot be described using A and B hyperfine constants and the hyperfine structure is therefore said to be anomalous. In this paper, we have studied the hyperfine structure of a few transitions in Al II, 3s5s(3)S-3s5p(3)P, 3s4d(3)D-3s5p(3)P and 3s5p(3)P-3s5d(3)D, by combining theory and experiment. It is shown that the anomalous hyperfine structure is due to strong off-diagonal hyperfine interaction resulting not only in a deplacement of the energies of the hyperfine levels, but also resulting in large intensity redistribution among the individual hyperfine lines. It is shown that the hyperfine mixing in 3s4d(3)D and 3s5d(3)D is very large, whereas small but not negligible in 3s5p(3)P. By combining experimental spectra and theory we could obtain accurate wavefunctions for the 3s4d(3)D and 3s5d(3)D hyperfine levels which were used to calculate the gf-values of all individual hyperfine transitions not only for 3s5p(3)P, but also for 3s3p(3)P and 3s4p(3)P, where the off-diagonal hyperfine interaction leads to negligible intensity redistribution.
41.	Andersson, T., et al. (författare) Electronic structure transformation in small bare Au clusters as seen by x-ray photoelectron spectroscopy 2017 Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 50:1 Tidskriftsartikel (refereegranskat)abstract Free bare gold clusters in the size range from few tens to few hundred atoms (<= 1 nm dimensions) have been produced in a beam, and the size-dependent development of their full valence band including the 5d and 6s parts has been mapped 'on the fly' by synchrotron-based photoelectron spectroscopy. The Au 4f core level has been also probed, and the cluster-specific Au 4f ionization energies have been used to estimate the cluster size. The recorded in the present work valence spectra of the small clusters are compared with the spectra of the large clusters (N similar to 10(3)) created by us using a magnetron-based gas aggregation source. The comparison shows a substantially narrower 5d valence band and the decrease in its splitting for gold clusters in the size range of few hundred atoms and below. Our DFT calculations involving the pseudopotential method show that the 5d band width of the ground state increases with the cluster size and by the size N = 20 becomes comparable with the experimental width of the valence photoelectron spectrum. Similar to the earlier observations on supported clusters we interpret our experimental and theoretical results as due to the undercoordination of a large fraction of atoms in the clusters with N similar to 10(2) and below. The consequences of such electronic structure of small gold clusters are discussed in connection with their specific physical and chemical properties related to nanoplasmonics and nanocatalysis.
42.	Arnold, Cord, et al. (författare) Nonlinear Bessel vortex beams for applications 2015 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 48:9 Tidskriftsartikel (refereegranskat)abstract We investigate experimentally and numerically the nonlinear propagation of intense BesselGauss vortices in transparent solids. We show that nonlinear Bessel-Gauss vortices preserve all properties of nonlinear Bessel-Gauss beams while their helicity provides an additional control parameter for single-shot precision micro structuring of transparent solids. For sufficiently large cone angle, a stable hollow tube of intense light is formed, generating a plasma channel whose radius and density are increasing with helicity and cone angle, respectively. We assess the potential of intense Bessel vortices for applications based on the generation of hollow plasma channels.
43.	Baev, A., et al. (författare) Nonlinear propagation of strong multi-mode fields 2003 Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 36, s. 3761-3774 Tidskriftsartikel (refereegranskat)abstract We develop a strict theory of nonlinear propagation of few interacting stronglight beams. The key idea of our approach is a self-consistent solution ofthe nonlinear wave equation and the density matrix equations of the materialbeyond the rotatory wave approximation. We assume a Fourier expansion ofthe density matrixwhich goes beyond the conventionalTaylor expansions of thepolarization over the field amplitudeswhich is inadequate for the field strengthsthat we are interested in. Two qualitatively different situations are considered,with and without phase matching. Unlike in our previous paper (Baev et al2003 J. Opt. Soc. Am. B at press) devoted to the three-photon (TP) absorptioninduced upconverted lasing, we obtain here a strict solution for the nonlinearinteraction between different light beams. The general theory is applied to anumerical study of the role of saturation in TP photoabsorption by an organicchromophore in solution.
44.	Balcou, P, et al. (författare) Quantum-path analysis and phase matching of high-order harmonic generation and high-order frequency mixing processes in strong laser fields 1999 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 32:12, s. 2973-2989 Tidskriftsartikel (refereegranskat)abstract We study phase-matching conditions for high-order harmonic generation as well as high-order sum- and difference-frequency mixing processes in strong laser fields, using a graphical approach described in Balcou et al (1997 Phys. Rev. A 55 3204-10). This method is based on the analysis of the different quantum paths that contribute, with different phase properties, to the single-atom response. We propose a simple numerical method to disentangle the quantum paths contributing to the generation process. We present graphical maps of the phase matching around the laser focus, which allow one to predict the geometries that optimize the conversion efficiency of the process considered. The method is applied to the study of sum- and difference-frequency mixing processes. The qualitative predictions of the graphical phase-matching approach are confirmed by numerical propagation calculations.
45.	Bao, Zhuo, et al. (författare) Detailed Theoretical and Experimental Description of Normal Auger Decay in O2 2008 Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 41:12, s. 125101- Tidskriftsartikel (refereegranskat)abstract The normal Auger electron spectrum of the O-2 molecule is assigned in detail on the basis of ab initio valence configuration interaction (CI) wavefunctions. Potential energy curves of the ground state, the core-ionized states and the doubly charged final states are calculated and Auger decay rates are obtained with the one-centre approximation. Using the lifetime vibrational interference method, band shapes are obtained for all contributions to the Auger spectrum. The calculated Auger electron spectrum allows us to identify all features observed experimentally. Significant differences to previous assignments are reported. A quantitative simulation of the spectrum is given on the basis of a curve-fitting procedure, in which the energetic positions and intensities of the theoretical bands were optimized. Besides providing a basis for a refined analysis of the spectrum, the fit allows us to assess the accuracy of the calculation. As expected for this level of theory, the absolute accuracy of the valence CI energies is found to be about 0.3 eV. The inherent error of the one-centre transition rates is less than 5% of the most intense transition in the spectrum. The frequently questioned one-centre Auger transition rates are shown to be rather appropriate if applied with reasonable wavefunctions and if the vibrational band structure of the molecular spectrum is properly taken into account.
46.	Biemont, E, et al. (författare) Experimental and theoretical energy levels, transition probabilities and radiative lifetimes in YbIII 2001 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 34:10, s. 1869-1876 Tidskriftsartikel (refereegranskat)abstract The analysis of the spectrum of Yb rn has been extended allowing us to establish 11 new energy level values. In addition, radiative lifetimes of two excited states of Yb III have been measured for the first time using time-resolved laser-induced fluorescence following two-photon excitation. The good agreement between experimental results and semi-empirical calculations performed with the relativistic Hartree-Fock method including core-polarization effects allows the determination of transition probabilities for 15 lines.
47.	Biemont, E, et al. (författare) Experimental lifetime determination in neutral praseodymium (Pr I) and neodymium (Nd I) 2004 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 37:7, s. 1381-1389 Tidskriftsartikel (refereegranskat)abstract Radiative lifetime measurements have been performed, with a time-resolved laser-induced fluorescence technique, for 18 even-parity levels of Pr I and 15 odd-parity levels of Nd I. The new results are compared with the few experimental data available in the literature and good agreement is found. However, fragmentary knowledge of the spectra prevents reliable calculation of branching fractions and calls for additional laboratory efforts in order to provide the astrophysicists with reliable transition probabilities needed for investigating the magnetic fields in chemically peculiar stars.
48.	Biemont, E, et al. (författare) Lifetime measurements for doubly ionized uranium 2002 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 35:7, s. 1701-1705 Tidskriftsartikel (refereegranskat)abstract The first lifetime measurements for doubly ionized uranium are reported in the present work. They relate to five levels belonging to the configurations 5f(2)6d(2), 5f(2)6d7s and 5f(3)7p and have been obtained with a time-resolved laser-induced-fluorescence technique, the ions being produced by laser ablation of a uranium oxide target.
49.	Biemont, E, et al. (författare) Lifetimes along perturbed Rydberg series in neutral thallium 2005 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 38:19, s. 3547-3558 Tidskriftsartikel (refereegranskat)abstract Radiative lifetimes of 15 Tl I levels belonging to the 6s(2)ns(2)S(1/2) (n = 7-14) and 6s(2)nd(2)D(3/2) Rydberg series (n = 6-12) have been measured using a time-resolved laser-induced fluorescence technique. All the measured levels have been excited from the ground state 6s(2)6p(2)P(1/2)(0) (odd parity) with a single-step excitation process. The general perturbation of the ns series by the 6s6p(2) configuration and the corresponding modification of the lifetimes are adequately reproduced by a theoretical model including core-polarization effects and combined with a least-squares fit to the observed energy levels. The general behaviour of the lifetime values for the 6s(2)np odd levels along the Rydberg series is also well reproduced. The use of the multiconfiguration quantum defect theory has allowed us to obtain lifetime values along the 6s(2)ns(2)S(1/2) series up to levels with n = 31.
50.	Brage, Tomas, et al. (författare) MCHF calculations of autoionization widths in two- and three-electron systems 1993 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 26:4, s. 621-640 Tidskriftsartikel (refereegranskat)abstract We present calculations of autoionization widths using a fully numerical multiconfigurational Hartree-Fock method (MCHF). Energy positions and autoionization rates are given for several doubly-excited states lying below the n = 2 threshold in He I and H-. Particular attention is given to orthogonality considerations in the computation of the autoionization widths. The method is extended to the 1s2p2 2D, 1s2s(3S)3d 2D and 1s2s(3S)4d 2D states of Li I. To the authors' knowledge, our MCHF value, 12.5 meV, is the first result obtained for the autoionization width of the 1s2s(3S)4d 2D state. Comparison is made with other theoretical results and with experimental values and we point out several inconsistencies between the two sets of results.

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