The HD spectrum near 2.3 μm by CRDS-VECSEL: Electric quadrupole transition and collision-induced absorption

•Exhaustive review of the HD transitions reported in the literature up to 20,000 cm−1.•First spectra recorded by high sensitivity CRDS-VECSEL near 2.3 μm.•First detection of the S(3) quadrupole electric transition of HD fundamental band.•Agreement with advanced ab initio calculations within experimental uncertainties.•Measurement of the HD collision induced absorption (CIA) near 4360 cm−1.

The HD absorption spectrum is investigated near 2.3 μm with the help of a newly developed Cavity Ring Down Spectrometer (CRDS) using a VECSEL (Vertical External Cavity Surface Emitting Laser) as light source. The HD CRDS spectra were recorded for a series of ten pressure values in the range 50-650 Torr. The sensitivity of the recordings - noise equivalent absorption of the spectra on the order of αmin ≈ 5 × 10−10 cm−1 - has allowed for the first detection of the S(3) quadrupole electric transition of the HD fundamental band, at 4359.940 cm−1. The line center determined with an uncertainty of 0.002 cm−1 agrees with the most recent theoretical calculations. The retrieved value of the line intensity (2.5 × 10−27 cm/molecule at 296 K) agrees within 12% with the ab initio values included in the HITRAN spectroscopic database. We take the opportunity of this contribution to provide an exhaustive review of seventy-three HD absorption lines previously detected up to 20,000 cm−1.From the pressure dependence of the baseline of the CRDS spectra, the binary absorption coefficient of the HD collision induced absorption band is determined to be 1.17(4) × 10−6 cm−1amagat−2 at 4360 cm−1.

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