Photodissociation of Gaseous NCl_3 at 193 and 249 nm

摘要

The optical absorption spectrum of gaseous NCl_3 was measured from 170 to 350 nm, and experiments were performed in which this molecule was irradiated with a pulsed laser at 193 nm and 249 nm. Photodissociation channels accessible at these wavelengths can produce fragments in singlet, doublet, or triplet manifolds of states. Photodissociation at 249 nm produces prompt banded emission in the visible and near-IR spectral regions that is tentatively ascribed to transitions in NCl_2, suggesting that the dissociation channel leading to doublet fragments (NCl_2 and Cl) is operative at this photolysis wavelength. The absence of emission from excited singlet states of NCl or excited triplet states of Cl_2 suggests that the singlet and triplet dissociation channels are not important at 249 nm. For photolysis at 193 nm, prompt emission is observed from both the a~1Δ and b~1Σ~+ excited states of NCl. No emission is observed from either NCl_2 or excited triplet states of Cl_2. A measure of the quantum yield for NCl(a~1Δ) production by the 193 nm photodissociation of NCl_3 was determined by observing the transfer of energy from excited NCl to iodine atoms in the pulsed photolysis system. This method suggests that the yield has a value of 0.8 ± 0.2.