Far infrared laser Stark spectroscopy of the Σ bending vibration of ArHCl

Abstract
A complete analysis of the FIR laser Stark/microwave double resonance spectrum of the Σ bending vibration of ArHCl is given. Hyperfine-resolved spectra of the R(0), R(1), R(2), and P(1) transitions were measured near 25 cm-1 for both chlorine isotopes. Accurate values for the band origins, rotational constants, dipole moments, and quadrupole hyperfine constants were obtained. Comparison with Hutson's close-coupling calculations provide very strong support for the existence of a secondary minimum in the intermolecular potential surface at the linear ArClH geometry.