VIBRATIONALLY STATE-SELECTIVE LASER-PULSE CONTROL OF ELECTRONIC BRANCHING IN OH(X-2-PI A(2)SIGMA(+)) PHOTOASSOCIATION/

The quantum dynamics of photoassociative collisions O(P-3) + H(S-2) co ntrolled by picosecond laser pulses is explored in the ground (X (2)Pi ) and excited (A (2)Sigma(+)) electronic states. Coupled Schrodinger e quations are solved for representative wavepackets using ab initio dat a for potentials and (transition) dipole moments. The effect of laser induced electronic transitions as well as the branching between produc ts in the two electronic states is investigated. It is shown that by o ptimal choice of the laser pulse parameters the ground state process c an be achieved with high efficiency (> 80%) and a vibrational state se lectivity very close to 100%. For the excited state, similar results c an be obtained by a two-pulse ''dump-pump'' strategy. The electronic b ranching ratio can be controlled by the frequency and the polarization of the laser pulses or the scattering energy of the collision pair. ( C) 1998 Elsevier Science B.V. All rights reserved.