PHOTODISSOCIATION SPECTROSCOPY OF ICN IN THE VACUUM-ULTRAVIOLET REGION

Photodissociation of ICN was investigated by the measurement of the ab solute cross section for the production of CN(B-2 Sigma(+)-X-2 Sigma()) emission in the wavelength range 107-175 nm (57000-94000 cm(-1)). T he observed excitation function of the CN(B-2 Sigma(+)-X-2 Sigma(+)) e mission displays congested structures, indicating a number of Rydberg and high-lying valence states correlating to the I + CN(B-2 Sigma(+)) dissociation channel. The relative cross section for the production of CN(A(2) Pi(i)) was also determined, The quantum yield for the CN(B-2 Sigma(+)) production was observed to increase with excitation energy u p from approximate to 0.01 at 59000 cm(-1) up to approximate to 0.05 a t 87000 cm(-1). The sudden decrease of the yield around 88000 cm(-1) c orresponds to the opening of the ionization channel of ICN. The CN(B-2 Sigma(+)-X-2 Sigma(+)) emission was found to be partially polarized w ith reference to the direction of the electric vector of the excitatio n radiation. The polarization measurement was used to identify the typ es of absorption transitions relevant to the photodissociation. On the basis of these measurements, the spectral assignments of the absorpti on bands below the first ionization potential were reexamined.