S-matrix analysis of non-resonant multiphoton ionisation of inner-valence electrons of the nitrogen molecule

We have used a strong field S-matrix theory to analyse the ionisation of in ner-Valence electrons of the nitrogen molecule in an intense laser pulse. T he results of calculations show that the laser-induced population distribut ion in the electronic states of the molecular ion is shifted towards lower vibrational levels as compared to a Franck-Condon distribution. This is fou nd to be due to the strong dependence of the rates of multiphoton ionisatio n on the ionisation potential. Theoretical results for the intensity depend ence of the strongest band head of the first negative band system of N-2(+) agree with experimental data. (C) 2001 Published by Elsevier Science B.V.