Spectroscopy and dynamics of rare gas-spherical top complexes .3. The infrared 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 has been recorded in a supersonic jet in the region of the SiH4 ν3, triply degenerate stretching vibration at ∼2189 cm-1. The Ne-SiH4 spectrum is complex with no obvious regular band structure; a previous paper has reported the assignment and analysis of bands correlating 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 bands were identified by the use of a theoretical intermolecular potential, with potential parameters determined by reference to the two bands previously fitted; and the relative magnitudes of the Coriolis interactions between the K sublevels within the bands determined by explicit calculation of the Coriolis matrix elements. Having fitted the bands to appropriate energy-level expressions, an effective anisotropic potential for the internal rotation of the SiH4 molecule within the complex was fitted to the total of 15 observed band origins. With a fixed R approximation, the V3 anisotropic term was found to be ∼30 cm-1, approximately one-third that of Ar-SiH4, reflecting the freer rotation of the SiH4 molecule when complexed with the less polarizable Ne atom. However, the overall quality of the fit was an order of magnitude worse than that for Ar-SiH4, indicating increased importance of the radial dependence of the Ne-SiH4 potential compared to that of Ar-SiH4. &#169; 1997 American Institute of Physics.