Berlin 2001 – wissenschaftliches Programm
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MO: Molekülphysik
MO 11: Theory: Structure and Dynamics
MO 11.4: Vortrag
Donnerstag, 5. April 2001, 16:30–16:45, H107
Strong-field induced bond softening and enhanced ionization in molecular hydrogen — •Alejandro Saenz — Fachbereich Chemie, Universität Konstanz, Fach M 722, 78457 Konstanz
The quantum mechanical description of molecules in a laser field is a formidable task. For the simplest stable molecule, H2, calculations had to resort to rather drastic simplifications like e. g. one-dimensional models. In the present work, a non-perturbative, fully correlated and three-dimensional ab initio method describing two-electron diatomic molecules in an electric field has been developed. This approach allows the calculation of e. g. Stark shifts and tunnelling ionization rates in the case of H2. Contrary to previous belief, it was found that H2 (and not only ions as H2+) can exhibit the phenomenon of bond softening, i. e. a weakening of the chemical bond due to the external field. Based on the relatively simple and intuitive explanation for this phenomenon for H2, it is concluded that bond softening can occur in most neutral, covalently bound diatomic molecules. The same is valid for a second truely molecular strong-field phenomenon: enhanced ionization. This sudden increase of the ionization rate when plotted against the internuclear distance is found to be due to the same (avoided) crossing of potential curves that causes the bond softening.