Spectroscopic study of the mixed rare-gas–molecule van der Waals trimer NeArHCl

Abstract

The van der Waals trimer NeArHCl was studied with a pulsed molecular beam Fourier transform microwave spectrometer. The trimer is of the type rare-gas–rare-gas′–linear molecule that is relatively unexplored and is of considerable importance for the understanding of new correction terms proposed in current investigations of nonadditive contributions in weakly bound molecular systems. Pure rotational spectra of four isotopomers of NeArHCl, i.e., 20NeArH 35Cl, 20NeArH 37Cl, 22NeArH 35Cl, and 20NeArD 35Cl were investigated. Nuclear quadrupole hyperfine structures due to the 35Cl, 37Cl, and D nuclei were observed and assigned. The resulting nuclear quadrupole coupling constants were used to provide information about the angular anisotropy of the NeArHCl potential energy surface. Structural parameters of the trimer were determined from the rotational constants obtained. A pseudotriatomic harmonic force field analysis was performed to provide qualitative frequency predictions of the heavy atom van der Waals vibrational motions. Information about the additive and nonadditive interactions from structural and force field analyses is discussed.