Experimental and theoretical studies of the CN–Ar van der Waals complex.

The CN–Ar van der Waals complex has been observed using the B ²Σ⁺-X ²Σ⁺ and A ²Π-X ²Σ⁺ electronic transitions. The spectra yield a dissociation energy of D₀^″=102±2 cm^-1 and a zero-point rotational constant of B₀^″=0.067±0.005 cm^-1 for CN(X)–Ar. The dissociation energy for CN(A)–Ar was found to be D₀^′=125±2 cm^-1. Transitions to vibrationally excited levels of CN(B)–Ar dominated the B-X spectrum, indicative of substantial differences in the intermolecular potential energy surfaces (PESs) for the X and B states. Ab initio PESs were calculated for the X and B states. These were used to predict rovibrational energy levels and van der Waals bond energies (D₀^″=115 and D₀^′=183 cm^-1). The results for the X state were in reasonably good agreement with the experimental data. Spectral simulations based on the ab initio potentials yielded qualitative insights concerning the B-X spectrum, but the level of agreement was not sufficient to permit vibronic assignment. Electronic predissociation was observed for both CN(A)–Ar and CN(B)–Ar. The process leading to the production of CN(A,ν=8,9) fragments from the predissociation of CN(B,ν=0)–Ar was characterized using time-resolved fluorescence and optical-optical double resonance measurements. [ABSTRACT FROM AUTHOR]