Infrared spectroscopy and inelastic recoil dynamics of OH radicals in complexes with ortho- and para-D-2

The rotationally resolved infrared (IR) spectrum of D-2-OH in its ground el ectronic state has been obtained in the OH overtone region at 1.4 mu m via IR-ultraviolet (UV) action spectroscopy. The pure OH overtone and combinati on bands involving intermolecular bending excitation were observed. The exp erimental spectrum was compared with IR transition frequencies computed fro m ab initio theory for o-D-2-OH and p-D-2-OH. The state-selective IR excita tion of D2-OH also serves to initiate inelastic and/or reactive scattering dynamics between the D-2 and OH partners under restricted initial orientati on conditions. Time- and frequency-resolved measurements of the OH (v = 1) fragments from vibrational predissociation showed that vibrationally activa ted D2-OH is short-lived and that the D-2 fragment is vibrationally excited as a result of an efficient near-resonant vibration-to-vibration energy tr ansfer process. The remaining 350 cm(-1) of available energy is disposed pr imarily as rotational excitation of OH. The OH fragments also exhibit a str iking lambda-doublet preference, revealing alignment of the unpaired p pi o rbital with respect to the OH rotation plane that changes with the intermol ecular state selected. The results are consistent with half-collisions that sample different restricted angular regions of the OH + D-2 potential ener gy surface for each of the initially prepared states.