-
M. F. Gharaibeh,
J. M. Bizau, D. Cubaynes,
S. Guilbaud,
N. El Hassan,
M. M. Al Shorman,
C. Miron,
C. Nicolas,
E. Robert,
C. Blancard,
B. M. McLaughlin
-
M. F. Gharaibeh,
J. M. Bizau, D. Cubaynes,
S. Guilbaud,
N. El Hassan,
M. M. Al Shorman,
C. Miron,
C. Nicolas,
E. Robert,
C. Blancard,
B. M. McLaughlin
-
M. F. Gharaibeh,
J. M. Bizau, D. Cubaynes,
S. Guilbaud,
N. El Hassan,
M. M. Al Shorman,
C. Miron,
C. Nicolas,
E. Robert,
C. Blancard,
B. M. McLaughlin
-
M. F. Gharaibeh,
J. M. Bizau, D. Cubaynes,
S. Guilbaud,
N. El Hassan,
M. M. Al Shorman,
C. Miron,
C. Nicolas,
E. Robert,
C. Blancard,
B. M. McLaughlin
[show abstract]
[hide abstract]
ABSTRACT: Absolute cross sections for the K-shell photoionization of C-like nitrogen ions were measured
by employing the ion–photon merged-beam technique at the SOLEIL synchrotron radiation
facility in Saint–Aubin, France. High-resolution spectroscopy with E/deltaE ~ 7000 was
achieved with the photon energy from 388 to 430 eV scanned with a band pass of 300 meV,
and the 399.4–402 eV range with 60 meV. Experimental results are compared with theoretical
predictions made from the multi-configuration Dirac–Fock and R-matrix methods. The
interplay between experiment and theory enabled the identification and characterization of the
strong 1s -> 2p resonances observed in the spectra.
-
M. F. Gharaibeh,
J. M. Bizau, D. Cubaynes,
S. Guilbaud,
N. El Hassan,
M. M. Al Shorman,
C. Miron,
C. Nicolas,
E. Robert,
C. Blancard,
B. M. McLaughlin
-
Journal of Physics Conference Series 11/2012; 399:012002.
-
C. Blancard,
Ph. Cossé,
G. Faussurier,
J.-M. Bizau, D. Cubaynes,
N. El Hassan,
S. Guilbaud,
M. M. Al Shorman,
E. Robert,
X.-J. Liu,
C. Nicolas,
C. Miron
[show abstract]
[hide abstract]
ABSTRACT: Absolute photoionization cross sections of Ar+, Ar2+, and Ar3+ ions have been measured in the 250–280 eV photon energy range. These results are compared to theoretical cross sections extracted from two new calculations we performed. They reproduce well the general behavior of the experimental spectra and the magnitude of the direct photoionization cross sections. However, the oscillator strength of the resonant structure in the spectra, dominated by 2p→3d transitions, is overestimated up to 80% by our calculations.
Phys. Rev. A. 04/2012; 85(4).
-
M. F. Gharaibeh,
J. M. Bizau, D. Cubaynes,
S. Guilbaud,
N. El Hassan,
M. M. Al Shorman,
C. Miron,
C. Nicolas,
E. Robert,
C. Blancard,
B. M. McLaughlin
[show abstract]
[hide abstract]
ABSTRACT: Absolute cross sections for the K-shell photoionization of C-like nitrogen
ions were measured by employing the ion-photon merged-beam technique at the
SOLEIL synchrotron radiation facility in Saint-Aubin, France. High-resolution
spectroscopy with E/$\Delta$E $\approx$ 7,000 was achieved with the photon
energy from 388 to 430 eV scanned with a band pass of 300 meV, and the 399.4 to
402 eV range with 60 meV.
Experimental results are compared with theoretical predictions made from the
multi-configuration Dirac-Fock (MCDF) and R-matrix methods. The interplay
between experiment and theory enabled the identification and characterization
of the strong 1s $\rightarrow$ 2p resonances observed in the spectra.
03/2012;
-
[show abstract]
[hide abstract]
ABSTRACT: Magnetic dichroism in the angular distribution has been demonstrated for single-electron photoemission from inner ns(2) subshells of gaseous atomic targets using the example of K-shell photoionization of polarized Li atoms laser prepared in the 1s(2)2p (2)P(3/2) excited state. The effect is pronounced for the conjugate shakeup and conjugate shakedown photoelectron lines, and less important, though observable, for the main and direct shakeup lines. The phenomenon is caused by configuration interaction in the final continuum state and is quantitatively described by the close-coupling R-matrix calculations.
Physical Review Letters 11/2011; 107(21):213001. · 7.37 Impact Factor
-
S Düsterer,
P Radcliffe,
C Bostedt,
J Bozek,
A L Cavalieri,
R Coffee,
J T Costello, D Cubaynes,
L F DiMauro,
Y Ding, [......],
F Grüner,
W Helml,
W Schweinberger,
R Kienberger,
A R Maier,
M Messerschmidt,
V Richardson,
C Roedig,
T Tschentscher,
M Meyer
[show abstract]
[hide abstract]
ABSTRACT: Two-color, single-shot time-of-flight electron spectroscopy of atomic neon was employed at the Linac Coherent Light Source (LCLS) to measure laser-assisted Auger decay in the x-ray regime. This x-ray-optical cross-correlation technique provides a straightforward, non-invasive and on-line means of determining the duration of femtosecond (>40 fs) x-ray pulses. In combination with a theoretical model of the process based on the soft-photon approximation, we were able to obtain the LCLS pulse duration and to extract a mean value of the temporal jitter between the optical pulses from a synchronized Ti-sapphire laser and x-ray pulses from the LCLS. We find that the experimentally determined values are systematically smaller than the length of the electron bunches. Nominal electron pulse durations of 175 and 75 fs, as provided by the LCLS control system, yield x-ray pulse shapes of 120±20 fs full-width at half-maximum (FWHM) and an upper limit of 40±20 fs FWHM, respectively. Simulations of the free-electron laser agree well with the experimental results.
New Journal of Physics 09/2011; 13(9):093024. · 4.18 Impact Factor
-
J M Bizau,
C Blancard,
M Coreno, D Cubaynes,
C Dehon,
N El Hassan,
F Folkmann,
M F Gharaibeh,
A Giuliani,
J Lemaire,
A R Milosavljević,
C Nicolas,
R Thissen
[show abstract]
[hide abstract]
ABSTRACT: Photoionization cross sections of halogen-like Kr+ and Xe+ ions have been measured in the photon energy range extending up to 15 eV above the threshold. Two different devices were used, a merged-beam set-up and an ion trap. Combination of the two techniques allows for the extraction of the pure ground state ionization cross section on an absolute scale. Multiconfiguration Dirac-Fock calculations reproduce the magnitude of the direct photoionization cross sections well.
Journal of Physics B Atomic Molecular and Optical Physics 01/2011; 44:-. · 1.88 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The generalized geometrical model for photoionization from polarized atoms is extended to include mixing of configurations in the initial atomic and/or the final photoion states. The theoretical results for angle-resolved linear and circular magnetic dichroism are in good agreement with new high-resolution photoelectron data for 3p−1 photoionization of potassium atoms polarized in the K 3p64s 2S1/2 ground state by laser optical pumping.
Journal of Physics B Atomic Molecular and Optical Physics 09/2010; 43(20):201002. · 1.88 Impact Factor
-
V Richardson,
J T Costello, D Cubaynes,
S Düsterer,
J Feldhaus,
H W van der Hart,
P Juranić,
W B Li,
M Meyer,
M Richter,
A A Sorokin,
K Tiedke
[show abstract]
[hide abstract]
ABSTRACT: We have observed the simultaneous inner-shell absorption of two extreme-ultraviolet photons by a Xe atom in an experiment performed at the short-wavelength free electron laser facility FLASH. Photoelectron spectroscopy permitted us to unambiguously identify a feature resulting from the ionization of a single electron of the 4d subshell of Xe by two photons each of energy (93±1) eV. The feature's intensity has a quadratic dependence on the pulse energy. The results are discussed and interpreted within the framework of recent results of ion spectroscopy experiments of Xe obtained at ultrahigh irradiance in the extreme-ultraviolet regime.
Physical Review Letters 07/2010; 105(1):013001. · 7.37 Impact Factor
-
M Meyer, D Cubaynes,
V Richardson,
J T Costello,
P Radcliffe,
W B Li,
S Düsterer,
S Fritzsche,
A Mihelic,
K G Papamihail,
P Lambropoulos
[show abstract]
[hide abstract]
ABSTRACT: Two-photon excitation of a single-photon forbidden Auger resonance has been observed and investigated using the intense extreme ultraviolet radiation from the free electron laser in Hamburg. At the wavelength 26.9 nm (46 eV) two photons promoted a 3d core electron to the outer 4d shell. The subsequent Auger decay, as well as several nonlinear above threshold ionization processes, were studied by electron spectroscopy. The experimental data are in excellent agreement with theoretical predictions and analysis of the underlying multiphoton processes.
Physical Review Letters 05/2010; 104(21):213001. · 7.37 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The partial photoionization cross section of the 2p ionization of laser-excited aligned as well as ground-state oriented Na atoms were determined by high-resolution photoelectron spectroscopy and compared to multi-configuration Dirac-Fock and Hartree-Fock calculations. The measurements of the linear alignment dichroism (LAD) and the linear magnetic dichroism (LMDAD) are in very good agreement with the theoretical results. Similar studies were undertaken for the 3p photoionization of atomic K.
Journal of Physics Conference Series 12/2009; 194(2):022027.
-
D. Cubaynes,
S. Guilbaud,
F. J. Wuilleumier,
M. Meyer,
E. Heinecke,
K. Riek,
P. Zimmermann,
M. Yalçinkaya,
S. Fritzsche,
S. I. Strakhova,
A. N. Grum-Grzhimailo
[show abstract]
[hide abstract]
ABSTRACT: High resolution angle-resolved photoelectron spectra from Na atoms laser excited and aligned in the Na∗ 2p63p 2P3/2 state are investigated experimentally and theoretically in the region of the Na+ 2p53p manifold. A prominent influence of the alignment on the relative line intensities is observed. The measured linear alignment dichroism is in good agreement with the theoretical results obtained in the multiconfigurational Dirac-Fock approximation as well as in a generalized geometrical model, which is extended to the description of angular distributions of photoelectrons from polarized atoms.
Phys. Rev. A. 08/2009; 80(2).
-
[show abstract]
[hide abstract]
ABSTRACT: The generalized geometrical model utilized for the interpretation of photoelectron spectra is extended to the photoionization from polarized atoms. Within this model, the linear magnetic and the linear alignment dichroisms in the photoemission are calculated. The theoretical results are compared to those obtained from high-resolution angle-resolved photoelectron spectra, which were recorded upon 2p−1 photoionization of sodium atoms oriented in the Na 2p63s 2S1/2 ground and Na* 2p63p 2P1/2 laser-excited states or aligned in the Na* 2p63p 2P3/2 state. Good overall agreement is found between theory and experiment.
Journal of Physics B Atomic Molecular and Optical Physics 08/2009; 42(17):171002. · 1.88 Impact Factor
-
A. Azima,
S. Düsterer,
P. Radcliffe,
H. Redlin,
N. Stojanovic,
W. Li,
H. Schlarb,
J. Feldhaus, D. Cubaynes,
M Meyer,
John Dardis,
Patrick Hayden,
Pádraig Hough,
Vincent Richardson,
Eugene T. Kennedy,
John T. Costello
[show abstract]
[hide abstract]
ABSTRACT: Using a noninvasive, electro-optically based electron bunch arrival time measurement at FLASH (free electron laser in Hamburg) the temporal resolution of two-color pump-probe experiments has been significantly improved. The system determines the relative arrival time of the extended ultraviolet pulse of FLASH and an amplified Ti:sapphire femtosecond-laser pulse at the interaction region better than 90 fs rms. In a benchmarking pump-probe experiment using two-color above threshold ionization of noble gases, an enhancement in the timing resolution by a factor of 4 compared to the uncorrected data is obtained.
Applied Physics Letters 05/2009; · 3.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We have measured the absolute photoionization cross sections of Fe2+ to Fe6+ ions in the photon energy range covering the first ionization threshold up to 160 eV. Particular interest is emphasized on the region of the 3p→3d excitations. The experimental data are compared to the results of calculations we have performed using a spectral opacity code, as well as to available R-matrix and one-electron calculations. It is shown that often the theoretical results tend to overestimate the intensity of the 3p→3d photoexcitations. An anomalously low value of the integrated oscillator strength is measured for Fe2+ ion.
Phys. Rev. A. 03/2009; 79(3).
-
[show abstract]
[hide abstract]
ABSTRACT: We present measurements of the absolute photoionization cross section of the neonlike Si4+ ion over the 110–184 eV photon energy range. The measurements were performed using two independent merged-beam setups at the super-ACO and ASTRID synchrotron-radiation facilities, respectively. Signals produced in the photoionization of the 2p subshell of the Si4+ ion both from the 2p6 1S0 ground state and the 2p53s 3P0,2 metastable levels were observed. Calculations of the 2p photoionization cross sections were carried out using a multi-configuration Dirac-Fock code. They give results in good agreement with the measured spectra. Comparison with other available theoretical results is also presented.
Phys. Rev. A. 03/2009; 79(3).
