On the description of nuclear dynamics in ionization of diatomic molecules in short strong electromagnetic fields

Abstract

A (1+1)-dimensional model of H+2 is employed to study the validity of the fixed and the classically moving nuclei approximations commonly applied in theoretical description of ionization of diatomic molecules in short, intense laser fields. Up to a certain threshold intensity the ionization probability is found to be in very good agreement between all models, even though there are some differences in the final electronic probability density. Beyond the threshold intensity the classical and fixed nuclei approximations are seen to be completely inadequate to describe the ionization process. A simple scaling relation for the threshold intensity is derived and shown to be in excellent agreement with the numerical results.

Evidence of nuclear motion in H2-like molecules by means of high harmonic generation

“…In order to investigate the dynamics of a H 2 -like molecule in the presence of an external laser field, we start by considering a simple 1D model for the molecule, treated beyond the fixed nuclei approximation. Since the nuclear mass M of the nuclei is much larger than the mass m of the electron, the nuclei will be considered as classical particles whose dynamics can be described by means of the Newton laws [7][8][9]. The 1D model is justified by assuming that the molecule has been previously aligned to the linearly polarized field [10,11].…”

“…The laser field induces a strong acceleration on the electrons, which are stimulated to emit electromagnetic radiation; the radiated power is given by the Larmor formula (9) where a i ( t ) is the quantum-averaged acceleration of the i-th electron and can be obtained by using the Ehrenfest theorem. The spectrum of the emitted radiation is (10) with ( ω ) as the Fourier transform of a i ( t ).…”