Comparison of R-dependent ionization and bond softening as mechanisms for creating vibrational coherence in hot molecules

We compare the vibrational coherence induced by R-dependent ionization, also known as Lochfrass, and bond softening in strong laser fields through numerical simulations. We calculate the pulse-width and intensity dependence of the vibrational amplitude and average internuclear separation at different temperatures. We also present experimental results on the intensity dependence of the vibrational motion induced in the ground electronic state of I-2, which agree with the calculations for Lochfrass. Finally, we compare trajectories of vibrational coherence from a thermal ensemble and a single state as a function of intensity in a phase diagram for the two schemes. We conclude that hot molecules produce stronger vibrational motion when excited by Lochfrass compared to bond softening and that Lochfrass can lead to vibrational cooling.