Photodissociation spectroscopy of ICN in the vacuum ultraviolet region

Abstract

Photodissociation of ICN was investigated by the measurement of the absolute cross section for the production of CN(B 2 Σ +-X 2 Σ +) emission in the wavelength range 107–175 nm (57000–94000 cm −1). The observed excitation function of the CN(B 2 Σ +-X 2 Σ +) emission displays congested structures, indicating a number of Rydberg and high-lying valence states correlating to the I + CN(B 2 Σ +) dissociation channel. The relative cross section for the production of CN(A 2 Π i) was also determined. The quantum yield for the CN(B 2 Σ +) production was observed to increase with excitation energy from 2~ 0.01 at 59000 cm −1 up to 2~ 0.05 at 87000 cm −1. The sudden decrease of the yield around 88000 cm −1 corresponds to the opening of the ionization channel of ICN. The CN(B 2 Σ +-X 2 Σ +) emission was found to be partially polarized with reference to the direction of the electric vector of the excitation radiation. The polarization measurement was used to identify the types of absorption transitions relevant to the photodissociation. On the basis of these measurements, the spectral assignments of the absorption bands below the first ionization potential were reexamined.