M. REZAEI, N. MOAZZEN-AHMADI, Department of Physics and Astronomy, University of Calgary, 2500 University Dr., N.W., Calgary, Alberta T2N 1N4, Canada; K. H. MICHAELIAN, Natural Resources Canada, CanmetENERGY, 1 Oil Patch Drive, Suite A202 Devon, Alberta, T9G 1A8, Canada; A. R. W. MCKELLAR, National Research Council of Canada, Ottawa, Ontario, K1A 0R6, Canada.

Spectra of the van der Waals trimers Ar2-N2O and Ne2-N2O are studied in the region of the N2O nu1 fundamental ( sim2224~cm-1) using a tunable quantum cascade laser to probe a pulsed supersonic expansion from a slit jet nozzle. Improved data are also obtained for the dimers Ar-N2O and Ne-N2O, with the latter representing a significant improvement on the best previous results. As well, a feature in the spectrum is tentatively assigned as the Q-branch of Ar3-N2O. The observed vibrational shifts for Nen-N2O are almost exactly linear for n~=~0-2. However, for Arn-N2O the n~=~2 band origin is slightly blue-shifted compared to the linear prediction, and the n~=~3 origin (if correct) is more significantly blue-shifted (by 0.09~cm-1).