PULSED-BEAM MICROWAVE FOURIER-TRANSFORM MEASUREMENTS ON ISOTOPICALLY SUBSTITUTED VAN-DER-WAALS DIMER NE-OCS

Pure rotational spectra of seven isotopomers of Ne-OCS (Ne-OCS, Ne-22- OCS, Ne-21-OCS, Ne-(OCS)-O-18, Ne-(OCS)-C-13, Ne-(OCS)-S-34, and Ne-(O CS)-S-33) have been investigated using a pulsed jet cavity microwave F ourier transform spectrometer. Rotational and centrifugal distortion c onstants have been determined for all species, as well as the nuclear quadrupole coupling constants of S-33 and Ne-21 in Ne-(OCS)-S-33 and N e-21-OCS, respectively. Harmonic force field analyses have been perfor med which account for the Variations in the distortion constants betwe en the isotopomers. Effective and ground state average structures have been obtained and are discussed in light of the nuclear quadrupole co upling constants and of dipole moment measurements. The determined cou pling constants have provided a means of comparing the effects of pert urbation of the electronic structures of both constituents upon comple xation. An electrostatic model has been applied to calculate the Ne-21 coupling constants and a possible source of their disagreement with e xperiment is discussed. (C) 1995 Academic Press, Inc.