Control of vibrational excitation and dissociation of small molecules by chirped intense inflared laser pulses

Abstract

The time-dependent Schrödinger equation describing the interaction of an HCN molecule with intense, ultrashort, chirped infrared laser pulses is solved numerically. The molecule is represented as two coupled Morse oscillators and the chirped laser pulse frequency ω( t) is adapted to the CH-bond anharmonicity in such a way that the pulse is nearly resonant with the vibration of this bond during the whole excitation process. It is shown that by controlling the chirping rate and the area of the pulse, one can selectively and efficiently excite and dissociate one particular bond and control the excitation of the other bond in a triatomic molecule. Such pulses should become important tools in photochemistry since one can thus prepare non-statistical quantum vibrational states and control the reactivity of a molecule by varying the laser phase.