Probing the Cl–HCl complex via bond-specific photodissociation of (HCl)2

Infrared–ultraviolet double resonance has been used to photodissociate the free HCl bond of the HCl dimer. This creates Cl–HCl in a coherent superposition of electronic and vibrational states. Measurement of the translational energy of the departing H atom using high-n Rydberg time-of-flight spectroscopy enables the Cl–HCl potential surfaces to be probed. The features thus obtained agree with theoretical estimates. At long IR–UV delays, the fastest H atoms derive primarily from UV photodissociation of internally excited HCl (e.g., high rotational levels) formed by (HCl)2 predissociation.