| 1. |
- Antoine, P, et al.
(författare)
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Generation of attosecond pulses in macroscopic media
- 1997
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 56:6, s. 4960-4969
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Tidskriftsartikel (refereegranskat)abstract
- We describe theoretically the generation of ultrashort (subfemtosecond) pulses using high-order harmonics of a laser pulse with a time-dependent degree of ellipticity. The single-atom response is calculated by using a low-frequency strong-field approximation. Propagation effects are taken into account using a method going beyond the slowly varying envelope approximation. Propagation modifies significantly the results obtained in the single-atom response and, in certain conditions, makes the generation of one attosecond pulse possible. We discuss prospects for the observation of these ultrashort pulses. [S1050-2947(97)09411-0].
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| 2. |
- Lynga, C, et al.
(författare)
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Temporal coherence of high-order harmonics
- 1999
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 60:6, s. 4823-4830
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Tidskriftsartikel (refereegranskat)abstract
- Systematic studies of the temporal coherence properties of high-order harmonic radiation are presented. These complement our previous investigations [Bellini et at, Phys. Rev. Lett. 81, 297 (1998)], where we showed the separation of the far-field pattern of high-order harmonics into two distinct spatial regions with different coherence times. Here we show how the coherence time of the inner and outer regions changes as a function of the harmonic order, the laser intensity, and the focusing conditions. Good agreement with the predictions of the semiclassical model of harmonic generation is obtained. [S1050-2947(99)10312-3].
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| 3. |
- Altucci, C, et al.
(författare)
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Frequency-resolved time-gated high-order harmonics
- 1998
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 58:5, s. 3934-3941
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Tidskriftsartikel (refereegranskat)abstract
- We report measurements of high-order harmonic spectra obtained with a 800-nm 150-fs loser pulse with a time-varying degree of ellipticity. The modulation of the polarization in time is achieved by using birefringent optics and self-phase modulation in a glass plate. We can create one or two temporal gates of a few femtoseconds width, during which the polarization is linear and harmonic emission is efficient. The harmonic spectra observed experimentally demonstrate that harmonics generated with linear polarization are frequency chirped. The values measured experimentally are consistent with theoretical predictions based on the strong field approximation. [S1050-2947(98)05511-5].
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| 4. |
- Lappas, D. G, et al.
(författare)
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Generation of attosecond xuv pulses in strong laser-atom interactions
- 1998
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 58:5, s. 4140-4146
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Tidskriftsartikel (refereegranskat)abstract
- The generation of radiation pulses that can be as short as 120 attoseconds is demonstrated theoretically. We have employed a two-dimensional exact solution of the Schrodinger equation that allows for arbitrary laser ellipticity. By manipulating the laser ellipticity in time, it is shown that one can control the wave-packet dynamics of the ejected atomic electron. The nonlinear interaction of the electron with the atomic core can thus be restricted to extremely short times. Photon energies up to 160 eV are generated. It is also shown that with a higher laser frequency, even shorter pulses can be produced. [S1050-2947(98)02211-2].
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| 5. |
- Henderson, M, et al.
(författare)
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Lifetimes of the 5d(9)6p levels in HgIII
- 1999
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 59:5, s. 4068-4070
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Tidskriftsartikel (refereegranskat)abstract
- We report measurements and theoretical calculations for the lifetimes of the 5d(9)6p levels in Hg nr with J = 0,2,3,4. This is an extension of earlier measurements of the lifetimes of the 5d(9)6p levels in Hg III with J = 1, and now provides data for all 12 of the levels. The results also provide an isoelectronic comparison with earlier studies of these levels in Au II of the Pt sequence, and a homologous comparison with earlier studies of the 4d(9)5p levels in Ag II, Cd III, and In IV in the Pd sequence. [S1050-2947(99)10905-3].
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| 6. |
- Gaarde, Mette, et al.
(författare)
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Spatiotemporal separation of high harmonic radiation into two quantum path components
- 1999
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 59:2, s. 1367-1373
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Tidskriftsartikel (refereegranskat)abstract
- We present a spatiotemporal analysis of high harmonic generation, showing evidence for the presence of several quantum path contributions to the atomic dipole moment. We show that the harmonic radiation can largely be described as a sum of two fields having a phase proportional to the intensity of the generating field. We compare our results to recent experimental results demonstrating this separation [M. Bellini et al., Phys. Rev. Lett. 81, 297 (1998)]. We show how the temporal and spatial coherence properties are influenced by this effect, and discuss how it could be used to obtain better control of the generated harmonic radiation. [S1050-2947(99)00402-3].
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| 7. |
- Roos, L, et al.
(författare)
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Controlling phase matching of high-order harmonic generation by manipulating the fundamental field
- 1999
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 60:6, s. 5010-5018
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Tidskriftsartikel (refereegranskat)abstract
- We study experimentally how to control and improve phase matching of high-order harmonic generation. We use a birefringent lens and a birefringent compensator to obtain a fundamental laser pulse (150 fs, 800 nm, similar to 4 mJ) With two foci Separated by 6.2 mm along the propagation axis and with a controllable phase delay between the polarizations along the optic axes of the birefringent optical components. This enables us to enhance the high-order harmonic conversion efficiency for the high-order harmonics in neon to 3 x 10(-8), a factor of 4 higher compared to a single-focus setup in similar conditions. The enhancement is achieved by improving the phase matching and at the same time maintaining a high intensity in a large generating volume. [S1050-2947(99)04512-6].
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| 8. |
- Abascal, Isabel Sainz, et al.
(författare)
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Bipartite entanglement measure based on covariance
- 2007
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 75:6
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Tidskriftsartikel (refereegranskat)abstract
- We propose an entanglement measure for two quNits based on the covariances of a set of generators of the su(N) algebra. In particular, we represent this measure in terms of the mutually unbiased projectors for N prime. For pure states this measure quantifies entanglement, we obtain an explicit expression which relates it to the concurrence hierarchy, specifically the I-concurrence and the three-concurrence. For mixed states we propose a separability criterion.
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| 9. |
- Abdullaev, Fatkhulla, et al.
(författare)
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Collective dynamics of Fermi-Bose mixtures with an oscillating scattering length
- 2019
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 99:3
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Tidskriftsartikel (refereegranskat)abstract
- Collective oscillations of superfluid mixtures of ultra cold fermionic and bosonic atoms are investigated while varying the fermion-boson scattering length. We study the dynamics with respect to excited center of mass modes and breathing modes in the mixture. Parametric resonances are also analyzed when the scattering length varies periodically in time, by comparing partial differential equation (PDE) models and ordinary differential equation (ODE) models for the dynamics. An application to the recent experiment with fermionic Li-6 and bosonic Li-7 atoms, which approximately have the same masses, is discussed.
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| 10. |
- Abdullaev, Fatkhulla, et al.
(författare)
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Faraday waves in quasi-one-dimensional superfluid Fermi-Bose mixtures
- 2013
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 87:2
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Tidskriftsartikel (refereegranskat)abstract
- The generation of Faraday waves in superfluid Fermi-Bose mixtures in elongated traps is investigated. The generation of waves is achieved by periodically changing a parameter of the system in time. Two types of modulations of parameters are considered: a variation of the fermion-boson scattering length and the boson-boson scattering length. We predict the properties of the generated Faraday patterns and study the parameter regions where they can be excited.
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| 11. |
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| 12. |
- Abramowicz, Marek A, 1945, et al.
(författare)
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Twin paradox on the photon sphere
- 2007
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Ingår i: PHYSICAL REVIEW A. - 1050-2947. ; 75:4
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Tidskriftsartikel (refereegranskat)
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| 13. |
- Acín, Antonio, et al.
(författare)
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Optimal randomness certification from one entangled bit
- 2016
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 93:4
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Tidskriftsartikel (refereegranskat)abstract
- By performing local projective measurements on a two-qubit entangled state one can certify in a device-independent way up to one bit of randomness. We show here that general measurements, defined by positive-operator-valued measures, can certify up to two bits of randomness, which is the optimal amount of randomness that can be certified from an entangled bit. General measurements thus provide an advantage over projective ones for device-independent randomness certification.
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| 14. |
- Adamashvili, G. T., et al.
(författare)
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Influence of non-Markovian relaxation processes on self-induced transparency: Memory function theory for optical solitons
- 2008
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 78:1
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Tidskriftsartikel (refereegranskat)abstract
- The influence of transverse relaxation on the resonance soliton (2 pi hyperbolic-secant pulse) in solids is considered. It is shown that memory effects can be considered in terms of generalized non-Markovian optical Bloch equations. The equations of self-induced transparency with a memory function are presented. Explicit forms for the first-order effects of this relaxation on the frequency shift and the pulse height of a resonant 2 pi soliton in solids are given and discussed. It is shown that memory effects do lead to a qualitative change in the dynamics of the influence of transverse relaxations on a 2 pi pulse in comparison to the McCall-Hahn theory and others. The dynamics of the changes of the inverse width of the pulse are obtained in both the Markovian and the non-Markovian cases with realistic parameters that can be achieved in current experiments.
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| 15. |
- Adesso, Gerardo, et al.
(författare)
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Coexistence of unlimited bipartite and genuine multipartite entanglement : Promiscuous quantum correlations arising from discrete to continuous variable systems
- 2007
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 76:2, s. 022315-
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Tidskriftsartikel (refereegranskat)abstract
- Quantum mechanics imposes 'monogamy' constraints on the sharing of entanglement. We show that, despite these limitations, entanglement can be fully 'promiscuous', i.e. simultaneously present in unlimited two-body and many-body forms in states living in an infinite-dimensional Hilbert space. Monogamy just bounds the divergence rate of the various entanglement contributions. This is demonstrated in simple families of N-mode (N >= 4) Gaussian states of light fields or atomic ensembles, which therefore enable infinitely more freedom in the distribution of information, as opposed to systems of individual qubits. Such a finding is of importance for the quantification, understanding and potential exploitation of shared quantum correlations in continuous variable systems. We discuss how promiscuity gradually arises when considering simple families of discrete variable states, with increasing Hilbert space dimension towards the continuous variable limit. Such models are somehow analogous to Gaussian states with asymptotically diverging, but finite squeezing. In this respect, we find that non-Gaussian states (which in general are more entangled than Gaussian states), exhibit also the interesting feature that their entanglement is more shareable: in the non-Gaussian multipartite arena, unlimited promiscuity can be already achieved among three entangled parties, while this is impossible for Gaussian, even infinitely squeezed states.
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| 16. |
- Adesso, Gerardo, et al.
(författare)
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Continuous variable entanglement sharing in noninertial frames
- 2007
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 76:6, s. 062112-
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Tidskriftsartikel (refereegranskat)abstract
- We study the distribution of entanglement between modes of a free scalar field from the perspective of observers in uniform acceleration. We consider a two-mode squeezed state of the field from an inertial perspective, and analytically study the degradation of entanglement due to the Unruh effect, in the cases of either one or both observers undergoing uniform acceleration. We find that for two observers undergoing finite acceleration, the entanglement vanishes between the lowest frequency modes. The loss of entanglement is precisely explained as a redistribution of the inertial entanglement into multipartite quantum correlations among accessible and unaccessible modes from a non-inertial perspective. We show that classical correlations are also lost from the perspective of two accelerated observers but conserved if one of the observers remains inertial.
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| 17. |
- Adesso, Gerardo, et al.
(författare)
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Entanglement in Gaussian matrix-product states
- 2006
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 74:3, s. 030305(R)-
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Tidskriftsartikel (refereegranskat)abstract
- Gaussian matrix product states are obtained as the outputs of projection operations from an ancillary space of M infinitely entangled bonds connecting neighboring sites, applied at each of N sites of an harmonic chain. Replacing the projections by associated Gaussian states, the 'building blocks', we show that the entanglement range in translationally-invariant Gaussian matrix product states depends on how entangled the building blocks are. In particular, infinite entanglement in the building blocks produces fully symmetric Gaussian states with maximum entanglement range. From their peculiar properties of entanglement sharing, a basic difference with spin chains is revealed: Gaussian matrix product states can possess unlimited, long-range entanglement even with minimum number of ancillary bonds (M=1). Finally we discuss how these states can be experimentally engineered from N copies of a three-mode building block and N two-mode finitely squeezed states.
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| 18. |
- Aguilar, A., et al.
(författare)
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Double photodetachment from the Cl[-]ion
- 2004
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 69:2
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Tidskriftsartikel (refereegranskat)abstract
- The correlated process involving the photodetachment of two electrons from the [Formula Presented] ion has been investigated over the photon energy range 20–45 eV. In the experiment, a beam of photons from the Advanced Light Source (ALS) was collinearly merged with a counterpropagating beam of [Formula Presented] ions from a sputter ion source. The [Formula Presented] ions produced in the interaction region were detected, and the normalized signal was used to monitor the relative cross section for the reaction. An absolute scale for the cross section was established by measuring the spatial overlap of the two beams and by determining the efficiency for collection and detection of the [Formula Presented] ions. The overall magnitude and shape of the measured cross section for this process agrees well with an R-matrix calculation. The calculation identifies the dominant mechanism leading to the production of the [Formula Presented] ion as being a direct nonresonant process involving the ejection of a pair of electrons from the valence shell. Less important is the indirect nonresonant process that involves the production and decay of core-excited and doubly excited states of the Cl atom in an intermediate step. Direct and indirect resonant mechanisms involving the excitation of a single [Formula Presented] core electron or more than one valence electron of the [Formula Presented] ion were found to be insignificant in the energy range studied.
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| 19. |
- Ahmed, Ergin H., et al.
(författare)
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All-optical cw quadruple resonance excitation: A coherently driven five-level molecular system
- 2009
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 79:6
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Tidskriftsartikel (refereegranskat)abstract
- We report here a continuous-wave, high-resolution, and all-optical quadruple resonance laser excitation experiment. To demonstrate this excitation technique, we have used an inhomogeneously broadened molecular sample (Na-2). We emphasize the enhanced ability afforded by the technique to reach new ranges of internuclear separation as well as access to a large range of molecular electronic states. Using the Autler-Townes split line shape of a rovibronic transition and the E field amplitude of the corresponding coupling laser, we have measured with high precision the absolute value of the molecular electronic transition dipole moment matrix elements, with more flexibility than the double and the triple resonance based excitation schemes used previously. This technique may also be used in a stimulated Raman adiabatic passage configuration for effective transfer of ultracold molecules, formed at long internuclear distance, to the lowest vibrational level of the ground electronic state.
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| 20. |
- Ahufinger, V., et al.
(författare)
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Disordered ultracold atomic gases in optical lattices : A case study of Fermi-Bose mixtures
- 2005
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 72:6
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Tidskriftsartikel (refereegranskat)abstract
- We present a review of properties of ultracold atomic Fermi-Bose mixtures in inhomogeneous and random optical lattices. In the strong interacting limit and at very low temperatures, fermions form, together with bosons or bosonic holes, composite fermions. Composite fermions behave as a spinless interacting Fermi gas, and in the presence of local disorder they interact via random couplings and feel effective random local potential. This opens a wide variety of possibilities of realizing various kinds of ultracold quantum disordered systems. In this paper we review these possibilities, discuss the accessible quantum disordered phases, and methods for their detection. The discussed quantum phases include Fermi glasses, quantum spin glasses, “dirty†superfluids, disordered metallic phases, and phases involving quantum percolation.
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| 21. |
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| 22. |
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| 23. |
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| 24. |
- Alagia, M., et al.
(författare)
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Probing the potential energy surface by highresolution x-ray absorption spectroscopy : The umbrella motion of the coreexcited CH3 free radical
- 2007
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Ingår i: Physical Review. A. - 1050-2947 .- 1094-1622. ; 76:2, s. 124305-
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Tidskriftsartikel (refereegranskat)abstract
- A detailed study of the umbrellalike vibration in inner-shell spectroscopy is presented. The high-resolution x-ray absorption spectrum for the lowest lying core excitation of the CH3 free radical was recorded. High quality potential energy surfaces (PES) for the initial and final states of the transition were calculated as a function of the symmetrical stretching and the umbrella deformation coordinates. The strong anharmonicity along the umbrella coordinate in the double-well region of the PES of the core excited state has a strong effect on the bending vibrational progressions. The excellent agreement between the experiment and theory allows an accurate spectroscopic characterization of the vibrational structure of the electronic transition, and the estimation of the umbrella inversion time of 149 fs.
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| 25. |
- Alhassid, Y, et al.
(författare)
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Fano interference and cross-section fluctuations in molecular photodissociation
- 2006
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Ingår i: Physical Review A. - 1050-2947. ; 73
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Tidskriftsartikel (refereegranskat)abstract
- We derive an expression for the total photodissociation cross section of a molecule incorporating both direct and indirect processes that proceed through excited resonances, and show that it exhibits generalized Beutler-Fano line shapes. Assuming that the closed system can be modeled by random-matrix theory, we derive the statistical properties of the photodissociation cross section and find that they are significantly affected by the direct processes. In the limit of isolated resonances, we find that direct processes suppress the correlation hole of the cross-section autocorrelation function and lead to a maximum in the cross-section distribution.
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