Molecular-bond hardening and dynamics of molecular stabilization and trapping in intense laser pulses.

We extend our previous study [Chem. Phys. Lett. 197, 413 (1992)] of the molecular stabilization in intense laser fields by considering the dynamical behavior of the H&+ molecules in intense femtosecond short laser pulses at 775 nm. Significant stabilization and population trapping of high-lying vibrational states and chemical bond hardening are predicted for both continuous-wave (cw) lasers and short laser pulses. While the intensity dependences of the laser-induced stabilization are essentially the same for both cases, the detailed wave-packet localization dynamics is quite different. The correlation of the time-dependent dynamics with the time-independent Floquet complex quasienergy results, the probability for localization, the pulse-width dependence of molecular stabilization, the proton kinetic-energy spectrum, as well as the contrary dynamical response of low- and high-lying states, are studied at length for intense short laser pulses. In addition, the dynamic origin of "bond-softening" (for low-lying vibrational states) and "bond-hardening" (for high-lying vibrational states) effects in intense laser fields are explored.