Influence of the duration and shape of an infrared laser radiation pulse on the dynamics of coherent excitation of a molecular vibrational mode

A theoretical analysis is made of several conditions for multiphoton excitation of a vibrational mode. The highest excitation efficiency is achieved using laser pulses of resonant duration which is governed by the vibrational anharmonicity and is in the picosecond range. Excitation by a chain of resonant-duration pulses can efficiently overcome frequency detuning and populate high vibrational levels. A high-power picosecond infrared laser pulse under conditions of multiphoton resonance can selectively excite a molecule from the ground state to specific high vibrational levels, leaving all the other levels almost unpopulated by the end of the pulse.