ELECTRONIC SPECTROSCOPY AND DYNAMICS OF THE CH D-NE VAN-DER-WAALS COMPLEX/

Rotationally resolved spectra for the ($) over tilde B-2 Sigma-X(2) Pi transition of CH/D-Ne have been recorded. Bands of the complex were o bserved in association with the monomer 0-0 and 1-0 transitions. Analy ses of the rovibronic structure show that the complex is weakly bound in both the ($) over tilde X and ($) over tilde B states. Excitation t o the ($) over tilde B state weakens and lengthens the intermolecular bond. Hindered internal rotation (HIR) was observed in the ($) over ti lde B state, which has a linear equilibrium geometry. Rotational predi ssociation was evident in spectra for the n = 2 HIR levels of CH/D-Ne, and the n = 1, K = 0 level of CH-Ne. The rotational levels of CH/D(X) -Ne were characterized by half-integer quantum numbers. In contrast, t he rotational levels of CH/D(X)-Ar are known to be consistent with int eger quantum numbers (G. W. Lemire, M. J. McQuaid, A. J. Kotlar and R. C. Sausa, J. Chem. Phys., 1993, 99, 91). Models of the angular moment um coupling in CH(X)-Rg complexes have been used to examine possible c auses for this qualitative difference.