Quantum-state-specific metastable time-of-flight as a probe of CO photodesorption from GaAs(100)

By exciting the ‘forbidden’ a 3Π ← X1Σ+ bands of CO with an intense ultraviolet laser pulse, neutral time-of-flight (TOF) distributions of single quantum states of CO can be obtained using long (> 10 cm) flight paths. This new method is applied here to surface photodesorption in order to simultaneously determine the rotational, vibrational and translational energy content of CO formed in the reaction CO/GaAs(100) + hv(248 nm) → CO(X1Σ+, v ⩽ 4, J ⩽ 24) + GaAs(100). Distinctly non-Boltzmanntranslational energy distributions were obtained for every observed quantum state of CO. Other state specific observations are discussed.