Electronic spectroscopy and predissociation mechanism of Ar–NO in the 3p Rydberg states Original Research Article

Ar–NO in the C̃ and D̃ states, which are correlated to two components of 3p Rydberg complex of NO, C 2Π and D 2Σ+, were studied by using a mass-resolved (2+1) or (1+1′) resonance enhanced multiphoton ionization (REMPI) technique. The REMPI excitation spectra were measured by monitoring parent Ar–NO+ or fragment NO+. The binding energies and the vibrational parameters are determined for the Ar–NO C̃ and D̃ states. The D̃ state was found to have surprisingly large D0 values of 1044 cm−1 for vNO′=0 and 1004 cm−1 for vNO′=1, which are larger than 940 cm−1 for Ar–NO+. From the analysis of these spectra, it was found that Ar–NO in the 3p Rydberg states predissociates into NO and Ar at different rates strongly depending on the Rydberg orbital character, the vibrational quantum number (vNO′) of NO moiety, and the intermolecular stretching quantum number (vstr′) of Ar–NO. Especially, the interaction of the 3p Rydberg states with the nearest-neighboring B̃ state plays an important role in these vNO′- and vstr′-dependent predissociation of Ar–NO C̃(vNO′=0, 1, 2) and D̃(vNO′=0, 1).