Posts Tagged ‘ionization’

stsm-SU-UAMSTSM by  Eva Lindroth and Tor Kjellsson, Stockholm University with Luca Argenti and Fernando Martín, Universidad Autonoma de Madrid
On November 15th, 2013 (7 days)


Time-dependent atomic photoionisation with a Multi-Configuration-Hartree-Fock close-coupling approach

This STSM concerned the collaboration between the COST nodes in Stockholm and Madrid to build a new program to solve the timedependent Schrodinger equation (TDSE) for  arbitrary poly-electronic atoms under the action of pulsed fields.

The program under  construction extends a Multi-Con guration-Hartree-Fock (MCHF) atomic-structure package to include the coupling to an ionized electron. It is based on close-coupling ionization states built from MCHF parent-ion states coupled to radial B-splines. Prior to the STSM, the package could already reproduce photoionization cross sections for arbitrary atoms with both the initial bound state and the final continuum states described
at the MCHF level as detailed in a recent publication [Carette, Dahlstrom, Argenti
and Lindroth 2013 Phys. Rev. A 87 023420].

As a result of the STSM:

  • The inclusion of the K-matrix package for the calculation of multichannelsingle-ionisation scattering states to resolve energetically and angularly the partial photoelectron spectra encoded in the electronic wave packetsobtained from simulations of pump-probe experiments on atoms was started. A similar integration technique was already successfully demonstrated in 2010 [Argenti et al. 2013, Phys. Rev. A 87 053405].
  • The user friendly setup of the package was tested
  • The benchmarking of neon- and argon photoionization, and especially the issue of how to obtain a correct energy position of the so-called Cooper minima in argon was discussed.

STSM by  Patrick O’’Keeffe, National Research Council of Italy (Rome) with Michael Meyer, European XFEL Hamburg
On August 19th, 2013 (6 days)
From ITALY to GERMANYstsm-POK-thumbnail

Multiphoton ionization combining radiation from synchrotrons and free electron and optical lasers

The principal scientific goal of the mission was to allow the applicant (Patrick O’Keeffe, National Research Council of Italy, Rome) and the host (Michael Meyer, European XFEL Hamburg, Germany) to collaborate with Alexei GrumGrzhimailo and Elena Gryzlova of the Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University in order to prepare a manuscript based on experimental results obtained during a beam time at the French synchrotron source, SOLEIL, on the two-photon resonant ionization of Xe combining synchrotron and optical laser light.

The novelty of the results lies in the fact that the angular distributions of the emitted electrons were measured in coincidence with the isotope resolved Xe ion formed in the same event. This allowed the photoelectron angular distributions of the nuclear spin (I) zero atoms to be separated from the non-zero I atoms. This has the important consequence that the effects of nuclear spin depolarization of the intermediate state due to precession of the electronic angular momentum about the total angular momentum vector can be eliminated. This allows the pure electronic dynamics of the photoionization to be isolated.

The manuscript prepared during the STSM was recently published in Physical Review Letters:
Isotopically Resolved Photoelectron Imaging Unravels Complex Atomic Autoionization Dynamics by Two-Color Resonant Ionization, P. O’Keeffe, E.V. Gryzlova, D. Cubaynes, G.A. Garcia, L. Nahon, A.N. Grum-Grzhimailo, and M. Meyer, Physical Review Letters, 111,  243002 (2013).


Figure: The raw photoelectron images for parallel linear polarizations of both SR and optical laser light of the photoelectrons taken in coincidence with the non-zero and zero nuclear spin isotopes of Xe. The images are shown as 3D representations in order to visualize clearly the effect of the nuclear spin on the photoelectron angular distribution. Copyright: American Physical Society.