High resolution infrared spectra of H2–Ar, HD–Ar, and D2–Ar van der Waals complexes between 160 and 8620 cm−1

Spectra of weakly bound hydrogen–argon complexes have been studied at high spectral resolution (0.04–0.10 cm−1) using a long-path (154 m), low-temperature (77 K) absorption cell and a Fourier transform infrared spectrometer. The observations cover a wide spectral range from the far-infrared D2–Ar S0(0) band at 180 cm−1 to the near-infrared H2–Ar S2(1) band at 8600 cm−1. Compared to earlier studies, the new results have considerably improved resolution and accuracy. They also extend to new regions, namely the first overtone band of H2 and the pure rotational band of H2 and D2, and they include weak transitions involving excitation of the van der Waals stretching motion. These data serve as a basis for determining a greatly improved three-dimensional intermolecular potential energy surface for the hydrogen–argon system in the following paper.