INFRARED AND MICROWAVE-SPECTRA OF THE N-2-PROPYNE VAN-DER-WAALS CLUSTER

The infrared spectrum of N-14(2)-CH3CCH in the 3.0-mu m region has bee n observed and the rovibrational transitions have been assigned for th e A (m = 0) and E (m = +/- 1) methyl top internal rotor states of this near slipped parallel van der Waals molecule. The E-state transitions were used to estimate the barrier to internal rotation as 10 cm(-1). The observed A-state microwave transitions of N-14(2)-CH3CCH, N-15(2)- CH3CCH, and N-15(2)-CH3CCD are split into doublets, This doubler split ting, which is too small to be observed in the infrared spectrum, is a ttributed to the internal motion of the N-2 moiety about an axis conne cting the centers-of-mass of the molecules in the cluster; i.e., the N -2 molecule relates out of the heavy atom plane of the cluster. The sp littings in the microwave spectra were fit to a barrier height of 71 c m(-1) for the hindered N-2 motion. (C) 1997 Academic Press.