The (2–0) R(0) and R(1) transition frequencies of HD determined to a 10⁻¹⁰ relative accuracy by Doppler spectroscopy at 80 K

Abstract

The Doppler broadened R(0) and R(1) lines of the (2–0) vibrational band of HD have been measured at liquid nitrogen temperature. The corresponding transitions frequencies are determined with an accuracy of a few tens of kHz.

The high-accuracy spectroscopy of H2 rovibrational transitions in the (2-0) band near 1.2 μm

“…5, a similar plot for the six (electric dipole) transitions of HD in the (2-0) band whose transition frequencies were recently measured at high accuracy. The experimental values obtained in the saturation regime 8,10,11 and in the Doppler regime 16,17 have a similar accuracy of a few tens of kHz. Very similar (meas.-calc.)…”

“…8,[10][11][12]14 As a result, accuracies on HD transition frequencies achieved in the saturation regime are similar to those obtained in the Doppler regime 15,16 in particular at low temperatures. 17 To the best of our knowledge, in the case of the H 2 major isotopologue, no RV transition frequencies have been reported with sub-MHz accuracy, so far. This situation results both from the above-mentioned weakness of the H 2 RV transitions and from the lack of recent measurements of H 2 spectra referenced to frequency standards.…”

“…Let us mention that the NGP pressure shift parameters of the Q1–Q4 lines agree with the values retrieved in ref. 17 using a Galatry profile (both NGP and Galatry profiles neglect speed-dependent effects).…”

“…8,10–12,14 As a result, accuracies on HD transition frequencies achieved in the saturation regime are similar to those obtained in the Doppler regime 15,16 in particular at low temperatures. 17…”

“…Accuracies better than 100 kHz level have been recently achieved by several groups for a few (2-0) transition frequencies in HD. [8][9][10][11][12][13][14][15][16][17] This level of accuracy represents about onethousandth of the Doppler width of the (2-0) HD transitions at room temperature. Part of the experimental studies was performed in saturation regime in order to circumvent this large Doppler broadening but underlying hyperfine components were found to lead to a dispersive-like spectral structure which limited the final accuracy on the line center determination.…”