Microwave spectroscopic investigation of the Ne–acetylene van der Waals dimer

Abstract

Rotational spectra of eight isotopomers of the Ne–acetylene van der Waals dimer were measured in the frequency range of 5 to 23 GHz, using a pulsed molecular beam Fourier transform microwave spectrometer. Transitions within both the Σ0 ground state and the Σ1 first excited van der Waals bending state were measured for the isotopomers containing HCCH and H13C13CH, respectively. For the Ne–DCCD isotopomers, Σ0 and Π1 transitions were recorded, indicating a reversal of the energy level ordering upon deuterium substitution. The observed transitions indicate a Coriolis perturbation of the Σ1 and Π1 energy levels. The Σ1/Π1 state is no longer metastable for the Ne–DCCH isotopomers, so only ground state transitions were recorded. Nuclear quadrupole hyperfine structures were observed and partially resolved for isotopomers containing deuterium nuclei. The measured transition frequencies were compared to the values obtained by Bemish et al. from an ab initio potential energy surface using nuclear dynamical calculations. [R. J. Bemish, R. E. Miller, R. Moszynski, T. G. Heijmen, T. Korona, P. E. S. Wormer and A. van der Avoird, J. Chem. Phys., 1998, 109, 8968].