Energy partitioning in photodissociation. Systematic study of rotational energy disposal in vacuum ultraviolet photodissociation of the cyanogen halides and HCN

Abstract

Rotational energy disposal in CN(B²Σ⁺)_{v= 0} produced through photodissociation of HCN, ClCN, BrCN and ICN has been measured under collision-free conditions and at high resolution over a wide range of absorbed wavelengths in the vacuum u.v. The experimental measurements include systematic variation of (i) the mass of the departing atom, (ii) the electronic character of the initially excited state, (iii) the magnitude of the available excess energy and (iv) the level of excitation of the bending mode in HCN (C¹A′). The results have been discussed in terms of Franck–Condon considerations and the constraints introduced by geometric changes on photo-excitation, and the requirements of energy and angular momentum conservation following photodissociation.