Quantitative determination of the (2,0) band of deuterium in the near infrared via off-axis ICOS

Near-infrared off-axis integrated cavity output spectroscopy (oa-ICOS) was used to study the S(0)–S(3) transitions of the (2,0) vibrational band of deuterium from 6000 to 6350 cm−1. By varying the gas pressure from 50 to 950 Torr, the transition line strengths, pressure shifts, and effects due to pressure narrowing were quantified. Likewise, by simultaneously measuring the cavity-enhanced absorption spectra of a well-characterized reference gases, the absolute frequencies of the deuterium quadrupole transitions were determined and used to refine the molecular parameters. These measurements have applications in astrophysics and the determination of fundamental molecular constants.