ROTATIONAL SPECTRA OF THE SIGMA-BEND STATES OF AR-H/DCL AND THE SIGMA-STRETCH OF AR-HCL

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 Cl-35/Cl-37 isotopes of both Ar-HCl and Ar-DCl in the lowest-SIGMA-bending state. The HCl results are in good agreement with previous tunable far-infrared work [J. Chem. Phys. 89, 1268 (1988)]. For (Ar-DCl)-Cl-35 and (Ar-DCl)-Cl-35 the rotational constants B and D and the quadrupole interaction CHI-(aa) (CI) 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. X(aa)(D) for the (Ar-DCl)-Cl-35 was found to be 132(7) kHz. Analysis of the Cl-35/Cl-37 isotope effects shows that the H(D) in H(D) Cl is pointed predominately away from the Ar. Measurement of the J = O --> 1 to J = 4 --> 5 transitions and their hyperfine structure for the SIGMA-stretch state of (Ar-H Cl)-Cl-35 give the rotational constants B, D, H, L, and the quadrupole interaction CHI-(aa)(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 pi-bending state.