The photodissociation of physisorbed alkyl nitrites.: Λ-doublet population and alignment of desorbed NO

The photolysis of thin layers of tert- and iso-butyl nitrite, physisorbed on a transparent insulating MgF2 surface, has been investigated. (1+1′)-Resonance-enhanced multiphoton ionization (REMPI) spectroscopy was used to characterize the desorbed NO. For high-J rotational levels, a preference for the Π(A″) Λ-doublet and a small degree of alignment is observed. The axis of alignment is found to be parallel to the plane of polarization of the photolysis laser and perpendicular to the surface normal, indicating a cartwheeling mode of desorption. The photofragment yield (PHOFRY) spectrum of iso-butyl nitrite is also reported.