Rotational spectra of the ∑ bend states of Ar–H/DCl and the ∑ stretch of Ar–HCl

Abstract

Rotational transitions of excited van der Waals states of Ar–H/DCl have been observed using the Balle–Flygare pulsed nozzle, Fourier transform, microwave spectrometer. Rotational constants and hyperfine interactions have been determined for the 35Cl/37Cl isotopes of both Ar–HCl and Ar–DCl in the lowest ∑ bending state. The HCl results are in good agreement with previous tunable far-infrared work [J. Chem. Phys. 89, 1268 (1988)]. For Ar–D35Cl and Ar–D37Cl, the rotational constants B and D and the quadrupole interaction χaa(Cl) were determined to be 1727.9887(1) MHz, 39.505(1) kHz, and −28.246(9) MHz, respectively, and 1686.4892(2) MHz, 39.167(4) kHz, and −22.344(10) MHz. χaa(D) for the Ar–D35Cl was found to be 132(7) kHz. Analysis of the 35Cl/37Cl isotope effects shows that the H(D) in H(D)Cl is pointed predominately away from the Ar. Measurement of the J=0→1 to J=4→5 transitions and their hyperfine structure for the ∑-stretch state of Ar–H35Cl give the rotational constants B, D, H, L, and the quadrupole interaction χaa(Cl) to be 1562.876(1) MHz, −67.2(1) kHz, −415(7) Hz, 1.6(1) Hz, and −20.774(7) MHz, respectively. The negative D centrifugal distortion constant and the large H and L constants suggest that this state is strongly perturbed by Coriolis interaction with the π bending state.