Measurement of Br photofragment orientation and alignment from HBr photodissociation: Production of highly spin-polarized hydrogen atoms.

The orientation and alignment of the 2P3/2 and 2P1/2 Br photofragments from the photodissociation of HBr is measured at 193 nm in terms of aq(k)(p) parameters, using slice imaging. The A 1Π state is excited almost exclusively, and the measured aq(k)(p) parameters and the spin-orbit branching ratio show that the dissociation proceeds predominantly via nonadiabatic transitions to the a 3Π and 1 3Σ+ states. Conservation of angular momentum shows that the electrons of the nascent H atom cofragments (recoiling parallel to the photolysis polarization) are highly spin polarized: about 100% for the Br(2P1/2) channel, and 86% for the Br(2P3/2) channel. A similar analysis is demonstrated for the photodissociation of HCl. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]