Lifetime of low vibrational levels of the metastable B²B2 state of H2O+ probed by photodissociation at 532 nm.

The decay of metastable states of the water radical cation H2O+ has been observed in an experiment that combines photofragment momentum imaging and electrostatic ion-beam trapping in a crossed-beam geometry. Photoabsorption of 532-nm laser light from a fast beam of H2O+ is observed to yield fragmentation into both OH0 + H+ and OH+ + H0. Using coincident photofragment momentum imaging, the initial state of the observed photofragmentation is associated with low vibrational levels of the second excited B²B2 state of H2O+, dissociating via absorption onto a repulsive part of the òA1 state. Electrostatic ion trapping in the laser interaction region is used to follow the photofragment intensity as a function of time and to determine the lifetime of the metastable states to be τB²B2 = 198 ± 11 μs. [ABSTRACT FROM AUTHOR]