CN(A 2Πi→X 2Σ+) and CN(B 2Σ+→X 2Σ+) yields from HCN photodissociation

The cross sections for the production of CN(A 2Πi→X 2Σ+) and CN(B 2Σ+→X 2Σ+) emissions from HCN photodissociation are measured using synchrotron radiation in the 1050–1550 Å region. The photoabsorption cross section of HCN is also measured, and the quantum yields for the emissions are determined. The spectra for the photoabsorption and photoemission cross sections are interpreted with the known excited states of HCN. Three new excited states are found from the CN emission quantum yields. It is observed that the vibrational population of the CN(B 2Σ+) photofragments produced by photodissociating HCN at Rydberg states are more vibrationally excited than those produced at other dissociative states. The photodissociation processes for producing CN emissions at various excited states are discussed.