The wavelength dependence of tert-butyl nitrite surface photochemistry

The surface photochemistry of tert-butyl nitrite adsorbed on Ag(111) was investigated at 532 and 266 nm. The desorbing molecules were detected in time of flight (TOF) mode by a mass spectrometer. Irradiation of the adsorbates leads to desorption of NO at both wavelengths. At these wavelengths caging and bimodal NO TOF distributions, consisting of a hyperthermal and a thermal component, are observed. At 532 nm dissociation is governed by a direct excitation with a cross section of 2 x 10^-21 cm². The observed TOF distributions at 266 nm are very similar to the 355 nm results, although generally higher translational energies and cross section values (2 x 10-¹⁹ cm²) were measured. At 266 nm dissociation proceeds via a direct excitation. The results are consistent with an excitation into the S₁ state at 355 nm and excitation into the S₂ state at 266 nm.