Vector correlations in the 308 nm photodissociation of ICN

Nascent Doppler profiles of CN (X2Σ+) fragments from the 308 nm photodissociation of ICN have been measured using high-resolution transient frequency modulated (FM) absorption spectroscopy. The complete set of vector correlations observable with linearly polarized single photon detection has been determined for several rotational states in ν = 0. All detected states exhibit strong positive velocity anisotropy indicating that the initial optical excitation is predominantly a parallel transition. The result challenges recent theoretical work which predicts that at wavelengths > 300 nm a perpendicular transition to the 3Π1 state dominates the dissociation.