TD09		15min10:54

TH. BRUPBACHER, W. JÄGER, M. C. L. GERRY, Department of Chemistry, University of British Columbia, Vancouver, B.C., V6T 1Z1, Canada; D. F. EGGERS, Department of Chemistry, University of Washington, Seattle, WA 98195, U. S. A..

\addtocountermpfootnote1 The microwave spectrum of the Xe-propyne Van der Waals complex has been recorded between 4---22~GHz, using a newly-developed pulsed molecular beam Fourier transform microwave spectrometer incorporating automated frequency scanning. The spectra of five isotopomers, involving ¹²⁹Xe, ¹³¹Xe, ¹³²Xe, ¹³⁴Xe, and ¹³⁶Xe, were observed in natural abundance.

The geometry of Xe-propyne is T-shaped, comparable to that of Ar -- propyne. Hindered internal rotation of the methyl group in propyne splits the levels into A and E species. The A species transitions could be analysed using predictions from an on-going analysis of the infrared spectrum. The microwave spectrum was analysed using a rotation-internal rotation Hamiltonian. The barrier to internal rotation V₃ was found to be ~ 22cm^-1, comparable to that of Ar-propyne.