Doppler spectroscopy of the OH fragment ejected by trans HONO (A 1A‘): Characterization of the A state resonances and determination of vibrational energy content of the NO fragment.

Resonances in the quasistable A 1A‘ state of trans HONO are probed through photodissociation experiments. The OH fragment ejected by HONO excited to specific –N[larger_closed_square]O stretching vibrational levels of the A state is probed by high-resolution sub-Doppler spectroscopy of the R2(1) (1,0) A 2Σ+–X 2Π transition. The Doppler profiles provide information on the vibrational state dependence of HONO’s subpicosecond fragmentation time and OH fragment’s kinetic energy. The latter is used to deduce NO sister fragment’s translational and vibrational energy content. These provide quantitative probes for (a) V→T ‘‘energy transfer’’ from the photoselected N[larger_closed_square]O vibrational coordinate to the recoil O–N coordinate and (b) N[larger_closed_square]O ‘‘vibrational relaxation’’ during dissociation. The present results and our previous measurements on the HONO A–X linewidths are discussed in terms of an excited-state potential energy surface in which (a) the –N[larger_closed_square]O coordinate is coupled to the reaction coordinate (O–N) and (b) there is a bottleneck in the exit channel. [ABSTRACT FROM AUTHOR]