TWO-PHOTON SPECTROSCOPY OF THE LOW LYING RYDBERG STATES OF NO: APPLICATION TO THE NO-AR COMPLEX

$^{a}$J. C. Miller, W. C. Cheng, J. Phys. Chem. 89, 1647 (1985). $^{b}$D. A. Mills, C. M. Western, and B. J. Howard, J. Phys. Chem. 90, 3331 (1986), ibd. 90, 4961 (1986). $^{c}$W. M. Fawzy and J. T. Hougen, J. Mol. Spectr. 137, 154(1989).Author Institution: Department of Physics and Astronomy, University of GeorgiaSeveral spectra of the NO-Ar complex in the wavelength region 320-365mm have been recorded under molecular beam conditions using (2+1) resonance enhanced multiphoton ionization detection. Bands around 360mm have been observed previously and assigned to an electronic state correlating with the different vibrational bands of the $C^{2}\Pi$ state of $NO.^{a}$ Additional band systems are found at shorter wavelengths which most likely, correlate with the NO Rydberg states: E $^{2}\Sigma, F^{2}\Delta$, and $H^{2}\Pi, ^{2}\Sigma$. All spectra are dominated by a progression in the NO - Ar stretch coordinate. Each member of a system exhibits similar substructure which we assign as rotational structure. The observed substructures are very different for each system due to the different character of the in involved electronic states. The rotational structure is analyzed in terms of a model (based on ref. b and c) which assumes that the two photon transition is carried solely by the NO moiety. The non-vanishing tensor components determined previously (see above) are transformed from the NO frame into the principal system of the nonlinear NO-Ar complex giving rise to new tensor components. Depending on the electronic state, small but significant deviations from the near T shaped ground state $structure^{b}$ are found