Strong-field approximation for Coulomb explosion of H{sub 2}{sup +} and D{sub 2}{sup +} by short intense laser pulses

We present a simple quantum mechanical model to describe Coulomb explosion of H{sub 2}{sup +} and D{sub 2}{sup +} by short, intense infrared laser pulses. The model is based on the length gauge version of the molecular strong-field approximation and is valid when the process of dissociation prior to ionization is negligible. The results are compared with recent experimental data for the proton kinetic energy spectrum [Th. Ergler et al., Phys. Rev. Lett. 95, 093001 (2005); D. S. Murphy et al., J. Phys. B 40, S359 (2007)]. Using a Franck-Condon distribution over initial vibrational states, the theory reproduces the overall shape of the spectrum with only a small overestimation of slow protons. The agreement between theory and experiment can be made perfect by using a non-Frank-Condon initial distribution characteristic for H{sub 2}{sup +} (D{sub 2}{sup +}) targets produced by strong-field ionization of H{sub 2} (D{sub 2}). For comparison, we also present results obtained by two different tunneling models for this process.