Selective photodissociation of O-H and O-D bonds from ground vibrational state of HOD using simple UV pulses

Abstract

Selective cleaving of both O-H and O-D bonds in HOD is achieved using reasonably simple UV pulses to excite the HOD molecule in its ground vibrational state to the repulsive first excited A~(¹B₁) surface. Detailed theoretical analysis of population transfer and flux in theH+O-D/H-O+D channels reveals an important preparatory role for the cross-talk between the participating levels and a possible role for the beat structure of the population transfer oscillations in facilitating selective dissociation. Excitation using a 50 fs single color 67169 cm^-1 laserpulse achieves a branching ratio H+O-D/H-O+D = 5.64 with 82% flux in the H+O-D channel and 15% in the H-O+D channel. A two color 50 fs laser pulse with frequencies of 54 920 and 52 303 cm^-1 provides a branching ratio of H-O+D/H+O-D = 2.83 and 52% flux in the H-O+D channel and 18% in the H+O-D channel.