Vector signatures of adiabatic and diabatic dynamics in the photodissociation of ICN

Nascent Doppler profiles of CN (X²Σ⁺) fragments from the à band photodissociation of room temperature ICN have been measured using high-resolution transient frequency modulated absorption spectroscopy. Results for dissociation at 222 nm, 248 nm, 266 nm, and 308 nm are presented. From the Doppler profiles of multiple CN states, we determine branching ratios of the coincident atomic iodine states, and bipolar moments characterizing the CN velocity and angular momentum anisotropy. The measurements provide sensitive tests of the strengths of optical coupling to the excited states contributing to the à band continuum, and the adiabatic and diabatic dynamics leading to the observed product states. Precise velocity measurements resolve differences in the average energy of the ICN molecules leading to selected fragment channels. We find a bond energy for ICN of 26980±100 cm^-1, somewhat higher than previous literature values.