Photodissociation of alkyl nitrites adsorbed on an MgF2 surface. Rotational and translational energy distributions of product NO(ν, J) molecules

The 351 nm photolysis of tert- and iso-butyl nitrite adsorbed on MgF2 held at 75 K has been investigated using resonance-enhanced multi-photon ionisation spectroscopy. Low desorption laser fluences were used to preclude thermal effects. The rotational distribution of desorbed NO(ν″ = 2) is velocity-dependent, being principally Gaussian at 2000 m s−1 and Boltzmann below 600 m s−1. The fast molecules suffer no collisions before desorption and their energy distributions are similar to those found in the gas phase. The slower molecules have suffered collisions. At intermediate velocities, the observed distribution is the sum of these two components which populate high and low rotational states respectively.