Osnabrück 2002 – scientific programme

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A: Atomphysik

A 18: Poster II

A 18.7: Poster

Thursday, March 7, 2002, 17:30–19:30, Schloss

Manifestation of the electron backscattering in the process of excess photon detachment of F⁻ — •Igor Kiyan and Hanspeter Helm — Fakultät für Physik, Albert-Ludwigs-Universität, D-79104 Freiburg

Negative fluorine ions are exposed to a strong infrared laser field of 1800 nm wavelength, 150 fs duration, and 10¹³ W/cm² peak intensity. An imaging technique is used to record an energy and angle resolved spectrum of photoelectrons produced in the process of photodetachment. The spectrum extends up to kinetic energies of approximately 11 eV, corresponding to absorption of more than 15 excess photons. The higher energy part of the spectrum is pronounced as a plateau localized within a small angle along the laser polarization axis. This plateau resembles the signal of photoelectrons which gain high kinetic energy in the process of backscattering from the residual core in the presence of the laser field. Calculations are performed using an improved Keldysh-like model, where the backscattering on a short range potential is taken into account. The result of these calculations, however, underestimates the observed effect by more than one order of magnitude. The role of the polarization forces in the process of backscattering will be discussed.