https://doi.org/10.1140/epjd/e2002-00135-x
Influence of the helium autoionization structures on the single/double ionization signal
1
Institute of Electronic Structure and Laser, FORTH, P.O. Box 1527, Heraklion, Crete 71110, Greece
2
Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
3
Dept. of Physics, Univ. of Crete, P.O. Box 1527, Heraklion, Crete 71110, Greece
Corresponding author: a nlambros@iesl.forth.gr
Received:
19
February
2002
Revised:
2
May
2002
Published online:
19
July
2002
Calculations of intense field (around 1016 W/cm2) single- and double-ionization
processes in helium at XUV wavelengths are presented. The laser wavelength is chosen
near the 
autoionization structure and the dynamics are explored.
Single and double ionization yields, as well as the photoelectron energy spectrum
for photon energies around the autoionization structure are calculated.
In the case of a pulse of few femtoseconds duration, no significant enhancement of the
double ionization yield has been found in tuning the photon frequency around the peak of the resonance.
It is also shown that in the case of a long pulse (and hence narrow compared with the relevant
autoionization width), the branching ratio of double to single ionization yield can be relatively
enhanced by tuning to the absorption minimum of the resonance.
PACS: 32.80.Rm – Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states) / 32.80.Dz – Autoionization
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2002
