SPECTROSCOPY AND DYNAMICS OF RARE GAS-SPHERICAL TOP COMPLEXES .3. THEINFRARED-SPECTRUM OF THE NU(3) BAND OF NE-SIH4 (J=1[-1 AND J=2[-1 TRANSITIONS)

The infrared spectrum of the rare gas-spherical top complex Ne-SiH4 ha s been recorded in a supersonic jet in the region of the SiH4 upsilon( 3) triply degenerate stretching vibration at similar to 2189 cm(-1). T he Ne-SiH4 spectrum is complex with no obvious regular band structure; a previous paper has reported the assignment and analysis of bands co rrelating with the SiH4 R(0) (K=0<--0, K=1<--0) and P(1) (K=0<--0, K=0 <--1) transitions. This paper concludes the study of Ne-SiH4, with the assignment and analysis of bands correlating with the SiH4 Q(1) (K=0< --0, K=1<--0, K=0<--1, K=1<--1) and R(1) (K=0<--0, K=1<--0, K=1<--1, K =2<--1) transitions. This was facilitated by a twofold approach: The b ands were identified by the use of a theoretical intermolecular potent ial, with potential parameters determined by reference to the two band s previously fitted; and the relative magnitudes of the Coriolis inter actions between the K sublevels within the bands determined by explici t calculation of the Coriolis matrix elements. Having fitted the bands to appropriate energy-level expressions, an effective anisotropic pot ential for the internal rotation of the SiH4 molecule within the compl ex was fitted to the total of 15 observed band origins. With a fixed R approximation, the V-3 anisotropic term was found to be similar to 30 cm(-1), approximately one-third that of Ar-SiH4, reflecting the freer rotation of the SiH4 molecule when complexed with the less polarizabl e Ne atom. However, the overall quality of the fit was an order of mag nitude worse than that for Ar-SiH4, indicating increased importance of the radial dependence of the Ne-SiH4 potential compared to that of Ar -SiH4. (C) 1997 American Institute of Physics.