Interference effects in the spectrum of HD: IV: the pure rotational band at room temperature

Abstract

The rotational spectrum of HD has been studied in absorption at room temperature for a density range of 6–57 amagat. Spectra were obtained in the 170- to 360-cm−1 region, including the R0(1), R0(2), and R0(3) transitions, with a 1-m path length and a spectral resolution varying from 0.05 to 0.20 cm−1. The observed line strengths were used to determine values for the dipole transition moments of HD in the range of 7.4 to 7.8 × 10−4 D, which is somewhat lower than currently accepted theoretical values of about 8.3–8.4 × 10−4 D. Only very small effects (≈0.2% per amagat) were found due to collisional interference on the line strengths; this result contrasts with much larger interference effects observed in the fundamental band, and it also casts some doubt on other recent studies of the rotational spectrum where larger interference effects were reported.