Photoinitiated decomposition of hydorxyalkyl radicals: Rydberg-valence interactions

The photoinitiated dynamics of hydroxyalkyl radicals is investigated on the ground and excited surfaces. Overtone excitation of four quanta of OH stretch vibration of the hydroxymethyl radical gives rise to O-H bond fission via tunneling, without prior isomerization to the methoxy radical. Excitation of hydroxyethyl radicals to the lowest $s$ and $p$ Rydberg excited states accesses dissociative states lying as low as 2.5 eV above the ground state. These states undergo conical intersections with each other and the ground state, which are much more efficient than comparable interactions in the hydroxymethyl radical, and display increased opportunities for accessing crossing seams. Both O-H and C-H bond fission channels are observed. Dissociation mechanisms involving direct and indirect bond fission, isomerization and nonadiabatic interactions will be discussed. Research supported by DOE.