Selective vibronic excitation and bond breaking by picosecond UV and IR laser pulses: application to a two-dimensional model of HONO2

A new method to control a bond-selective dissociation is presented: first, an optimal UV laser pulse accomplishes vibrationally state-selective comple te population transfer from the ground to the excited electronic state and, second, an optimal IR laser pulse induces an efficient bond-selective mult iphoton dissociation. The method is demonstrated by means of computer simul ation within the Schrodinger wavefunction formalism for a two-dimensional m odel of HONO2 wherein the OH and ON single-bond stretches are treated expli citly. Selective breaking of the ON single bond is achieved on a picosecond timescale, with the dissociation probability being almost 100%. The propos ed control scheme is much less demanding of the field strength of the disso ciating IR laser as compared to that required for breaking the ON single bo nd solely in the ground electronic state. (C) 1999 Elsevier Science B.V. Al l rights reserved.