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Sökning: WFRF:(Bässler M.)

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1.
  • Guo, J. H., et al. (författare)
  • Characterization of undulator radiation at MAXII using a soft X-ray fluorescence spectrometer
  • 1999
  • Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0168-9002. ; 431:1, s. 285-293
  • Tidskriftsartikel (refereegranskat)abstract
    • A grazing-incidence grating spectrometer has been used for the investigation of the undulator radiation from beamline 411 at MAX-lab. The direct detection of undulator light is expected to obtain the information of the quality of the undulator. Regular undulator radiation and some higher harmonics were observed. The effects of electronic beam coupling and Landau cavities have been studied. The experiment presents an easy and quick method to characterize the undulator radiation before the permanent monochromator is installed.
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2.
  • Miron, C., et al. (författare)
  • Nuclear motion driven by the Renner-Teller effect as observed in the resonant Auger decay to the X̃2Π electronic ground state of N2O
  • 2001
  • Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 115:2, s. 864-869
  • Tidskriftsartikel (refereegranskat)abstract
    • The nuclear dynamics in the Nt 1s→π* in nitrous oxide was studied using the high resolution resonant Auger spectroscopy and ab initio quantum chemical calculations. For probing the nuclear motion of the system in the core-excited state, the frequency detuning technique was used. The results showed changes in vibrational structure for the Auger decay spectra and a strong influence of nuclear motion on the electronic decay.
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3.
  • Björneholm, O., et al. (författare)
  • Doppler splitting of in-flight auger decay of dissociating oxygen molecules : The localization of delocalized core holes
  • 2000
  • Ingår i: Physical Review Letters. - : AMERICAN PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 84:13, s. 2826-2829
  • Tidskriftsartikel (refereegranskat)abstract
    • By exploiting the core-excitation-induced dissociation of O-2, we find that the Auger emission exhibits a Doppler-like energy shift. We show this to be a manifestation of localization of the core hole and propose that the problem of core-hole localization versus delocalization in core-hole spectroscopies may be resolved by considering the nature of the measurement.
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4.
  • Bässler, M., et al. (författare)
  • Beam line I411 at MAX II - Performance and first results
  • 2001
  • Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0168-9002. ; 469:3, s. 382-393
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the characteristics and first results from the soft X-ray beam line I411, based on an undulator at the third generation synchrotron facility MAX II, Sweden. The beam line is designed for high-resolution, angle-resolved electron spectroscopy on gases, liquids and solids. Main components are the modified SX700 monochromator and the end station, both of which were previously used at beam line 51 at MAX I. The end station is equipped with a rotatable SES-200 hemispherical electron-analyser. Before the end station, a one-metre section is reserved for exchangeable experimental set-ups. The usable photon energy range is 50-1500 eV and the photon flux is two orders of magnitudes higher compared to beam line 51. At 400 eV a resolving power of about 5700 in the first order of the monochromator grating could be obtained. In gas phase, a total electron energy resolution of 16 meV has been achieved. Detailed results on the undulator performance, flux, photon and electron energy resolution as well as some technical details are presented here. As an example of the capabilities of the beam line I411, we present the fully vibrationally resolved Auger resonant Raman electron spectrum of gas-phase N 2.
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5.
  • Bässler, M., et al. (författare)
  • Soft x-ray undulator beam line 1411 at MAX-II for gases, liquids and solid samples
  • 1999
  • Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 101-103, s. 953-957
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the build-up of the new undulator beam line 1411 at the third-generation synchrotron radiation facility MAX II in Lund, Sweden. This beam line is based on an upgraded version of the modified SX700-monochromator and the end station which were installed previously at beam line 51 at MAX I. The end station is equipped with a rotatable Scienta hemispherical electron-analyser making angle-resolved high resolution electron spectroscopy possible for various kinds of samples. The beam line performance will be considerably improved on MAX II due to a new undulator and the superior light source properties, e.g. the small vertical electron beam size. Undulator spectra have been measured and estimates of the photon flux at the experiment and the expected energy resolution are presented. The parameters for a new refocusing mirror were defined by ray tracing using the beam waist of the undulator. The beam line length was extended by 1 m to offer additional space for exchangeable experimental chambers.
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6.
  • De Brito, A. N., et al. (författare)
  • Evidence against atomiclike resonant auger decay in N2 doubly excited core states by high-resolution experiments
  • 2001
  • Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947. ; 64:5, s. 547021-547024
  • Tidskriftsartikel (refereegranskat)abstract
    • The resonant Auger decay spectra associated with doubly excited core-hole states near the N 1s threshold in the nitrogen molecule was measured. Electron-yield spectrum was obtained by setting a kinetic-energy window at 384 eV and scanning across the threshold region. At ground 410, 414, and 416 eV, photon energy, three dominant structures were observed. The increased signal-to-background ratio, intensity and resolution at third generation facilities were found to cast a different light on the dynamics of core photoionization in molecules.
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7.
  • Feifel, R., et al. (författare)
  • "Hidden" vibrations in CO : Reinvestigation of resonant Auger decay for the C 1s → π* excitation
  • 2002
  • Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 1050-2947. ; 65:5 A, s. 527011-527018
  • Tidskriftsartikel (refereegranskat)abstract
    • The higher vibrational levels of the C 1s→π* excitation in carbon monooxide (CO) were investigated by using resonant Auger electron spectroscopy. The absorption profile of the CO was recorded in the partial electron yield mode. The results showed that the vibrational states were not seen in a total yield absorption spectrum whereas they were shown to be discernable in a partial electron yield spectrum.
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9.
  • Hjelte, I., et al. (författare)
  • Evidence for ultra-fast dissociation of molecular water from resonant Auger spectroscopy
  • 2001
  • Ingår i: Chemical Physics Letters. - 0009-2614. ; 334:1-3, s. 151-158
  • Tidskriftsartikel (refereegranskat)abstract
    • We present direct evidence for ultra-fast dissociation of molecular water in connection photo-excitation of the O1s→4a1 resonance. The core-excited H2O molecules are shown to dissociate into core-excited O*H and neutral H on a time scale comparable to the core hole lifetime, i.e. a few femtoseconds. This conclusion is based on a resonant Auger study, qualitative arguments and ab initio calculations. 'Hot bands' connected to Auger transitions from vibrationally excited OH fragments are identified, and these exhibit a dynamical behavior which qualitatively follows the change in excess energy.
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11.
  • Ovaskainen, Otso, et al. (författare)
  • Global Spore Sampling Project: A global, standardized dataset of airborne fungal DNA
  • 2024
  • Ingår i: Scientific Data. - 2052-4463. ; 11
  • Tidskriftsartikel (refereegranskat)abstract
    • Novel methods for sampling and characterizing biodiversity hold great promise for re-evaluating patterns of life across the planet. The sampling of airborne spores with a cyclone sampler, and the sequencing of their DNA, have been suggested as an efficient and well-calibrated tool for surveying fungal diversity across various environments. Here we present data originating from the Global Spore Sampling Project, comprising 2,768 samples collected during two years at 47 outdoor locations across the world. Each sample represents fungal DNA extracted from 24 m3 of air. We applied a conservative bioinformatics pipeline that filtered out sequences that did not show strong evidence of representing a fungal species. The pipeline yielded 27,954 species-level operational taxonomic units (OTUs). Each OTU is accompanied by a probabilistic taxonomic classification, validated through comparison with expert evaluations. To examine the potential of the data for ecological analyses, we partitioned the variation in species distributions into spatial and seasonal components, showing a strong effect of the annual mean temperature on community composition.
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12.
  • Piancastelli, M. N., et al. (författare)
  • Bond-distance-dependent decay probability of the N 1s -> pi* core-excited state in N-2
  • 2000
  • Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 33:9, s. 1819-1826
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the observation of the unusually weak decay of the N 1s --> pi* core-excited N-2 molecule to the (B) over tilde (2)Sigma(u)(+) final state of N-2(+), which is only detectable in an experiment with high sensitivity. The resonant Auger spectra exhibit an unexpected dependence on the selected vibrational level of the intermediate state. Theoretical calculations show that the interference between direct and resonant photoemission as well as a strong geometry dependence of the decay probability on the bond distance give rise to the observed features.
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13.
  • Rosenqvist, L., et al. (författare)
  • Femtosecond dissociation of ozone studied by the Auger Doppler effect
  • 2001
  • Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 115:8, s. 3614-3620
  • Tidskriftsartikel (refereegranskat)abstract
    • The peaks arising from the decay of the excited oxygen atom were studied. Fast dissociation of core-excited ozone was confirmed by the presence of Auger emission from atomic oxygen in the decay spectrum from the ozone OT 1s-σ*(7a1) state. No such emission was observed after excitation of the corresponding state on the central oxygen atom. An angle-dependent energy shift of the atomic lines was observed. Analysis of the energy shift revealed that the kinetic energy released in the dissociation process is approximately 3.3 ± 0.3eV. An energy release of 8.45 was found by application of a Born-Haber cycle.
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14.
  • Sałek, P., et al. (författare)
  • Resonant X-ray Raman scattering involving avoided crossings in the final-state potential-energy curves
  • 2000
  • Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 1050-2947. ; 62:6, s. 62501-62506
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of avoided crossings on the spectral profiles of resonant X-ray Raman scattering was investigated. The theory was also applied to nitrogen molecule in the core-excited level to analyze the electron decay process. The dependence of internuclear distance on electron transition amplitude was considered important with respect to the breakdown process of the transition. The correlation between the nuclear and electronic degrees of freedom was also reported.
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17.
  • Sorensen, S. L., et al. (författare)
  • High-resolution excitation-energy-dependent study of the Auger decay of the O 1s-1πg core-excited state in oxygen
  • 2001
  • Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947. ; 64:1, s. 127191-127199
  • Tidskriftsartikel (refereegranskat)abstract
    • The decay of bound core-excited states in molecular oxygen were investigated under Auger resonant Raman conditions. The lifetime-vibrational interference and bond-length dependence of the Auger transition rates were used to analyse the decay spectra. The final statess belonged to the molecular electronic structure and were observed to follow the Raman-Stokes dispersion law.
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18.
  • Wang, H., et al. (författare)
  • Filtering core excitation spectra : Vibrationally resolved constant ionic state studies of N 1s → 2π core-excited NO
  • 2001
  • Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 34:22, s. 4417-4426
  • Tidskriftsartikel (refereegranskat)abstract
    • High-resolution electron spectroscopy studies of the NO molecule in the regions of the N 1s → 2π core excitations have been performed. By selecting electrons within certain binding energy ranges, either the Auger electron yield - a good approximation for the x-ray absorption spectrum - or the electrons emitted after decay to a particular ionic final state (constant ionic state (CIS)) were detected. By selecting the X 1Σ+ (2π0) final state, the superposition of several intermediate state can be disentangled by exploiting a selection rule which permits only two of the three dipole-allowed intermediate states to decay to this specific final state. This makes it possible to obtain more detailed information on the potential energy curves of the intermediate states than is available from regular absorption measurements. We have also obtained CIS spectra for individual vibrational sublevels within this state. The role of lifetime vibrational interference on the appearance of these spectra is discussed.
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19.
  • Burmeister, F, et al. (författare)
  • Nonadiabatic effects in photoelectron spectra of HCl and DCl. I. Experiment
  • 2002
  • Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 65:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The HCl inner-valence photoelectron band at 26 eV binding energy has been recorded at high resolution. Discrete peaks arising from at least two separate vibrational progressions are superimposed on the broad continuum. Fano profiles are visible in one of the progressions. This indicates interference between superimposed electronic states, where weak avoided crossing allows two adiabatic states to couple. In the isotopic DCl molecular spectrum, the discrete lines are less pronounced, due to slower dissociation and therefore less coupling between the continuum and the bound state.
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21.
  • Denecke, R., et al. (författare)
  • Beamline 1511 at MAX II, capabilities and performance
  • 1999
  • Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - 0368-2048. ; 101-103, s. 971-977
  • Tidskriftsartikel (refereegranskat)abstract
    • The new undulator beamline 1511 at MAX-lab, now under commissioning, has been optimized for X-ray emission and photoelectron spectroscopies. Using an SX-700 high flux monochromator the accessible photon energy range is from 90 eV to about 1500 eV. The performance of the undulator agrees very well with the specifications, as shown by measurements using a photodiode. The energy resolution of the monochromator has been checked using absorption measurements in a gas cell. It was found to meet the expectations and exceeds a resolving power of 10 000 at 244 eV. The photon flux as a function of energy has been recorded as well and gives a maximum flux of 3×1013 photons/s/100 mA/0.1% BW. Beamlines 1511 and 1411 will be the first synchrotron beamlines making use of a so-called beam waist phenomenon, known from laser physics. We show results of ray-tracing calculations to determine the ultimate spot size on the sample location. The endstations to be used at this new beamline and their capabilities will be discussed as an example of the future use of this facility.
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24.
  • Feifel, Raimund, et al. (författare)
  • Interference Quenching of v
  • 2002
  • Ingår i: Physical Review Letters. ; 89:10, s. 103002-1
  • Tidskriftsartikel (refereegranskat)
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  • Resultat 1-25 av 31

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