Multi-photon excitation dynamics of molecules using long and short laser pulses.

摘要

The dynamical behavior of molecules by multi-photon excitation upon interaction with laser fields has been investigated in this thesis. The excitation dynamics was studied using the photofragment imaging technique called velocity mapping.; We observed several new features in the velocity and angular distributions of the photofragments, arising from above-threshold dissociative ionization. The fragmentation dynamics was governed by the excitation of doubly excited Rydberg states, producing a continuous and highly anisotropic distribution of energies peaked at zero kinetic energy.; Dynamical alignment of rotational wavepackets was explored using intense, ultrashort laser pulses. The effect of alignment on the angular distribution of the photofragments was probed at various time delays between the pump and probe pulses, by velocity mapping. Enhanced ionization, parallel to the aligning field direction, was also investigated by monitoring the ion signal as a function of the pump-probe delay.