Hyperfine transitions in the first overtone mode of hydrogen deuteride

Abstract

Beyond the metrology and computational challenges associated with molecular hydrogen, key data are expected to assess the physics of simple molecular systems, and even the New Physics beyond the Standard Model. To assist the deciphering of Doppler-free spectra obtained at very high accuracy (∼ 10 −9), we report on hyperfine transitions of HD in the lowest vibrational levels of the ground electronic state. Using the spin-rotation, nuclear spin-spin and quadrupolar hyperfine couplings determined by means of high-level quantum-chemical calculations, the hyperfine energy levels, and the associated line intensity have been obtained by using tensorial momentum algebra. To illustrate our purpose, the hyperfine line intensity of two specific transitions (P 1 and R 1) belonging to the first overtone of HD is reported and commented on. The calculated stick spectra emphasize the experimental challenge (in terms of sensitivity and of spectral resolution) associated with the spectral analysis, because the lines can be apart by less than 10 kHz.

Lamb-peak spectrum of the HD (2-0) P(1) line

“…1. Our analysis of the hyperfine structure of this P(1) line is found to be in excellent agreement with that of other recent analyses [28,29].…”

Sub-ppb measurement of a fundamental band rovibrational transition in HD

“…Band origins T v and rotational constants B v and D v are determined by fitting the energies calculated by the program H2Spectre [1] for the first three rotational levels in each vibrational state. The hyperfine parameters c H,v , c D,v , eQq 0,v , and S v ("c dip ") are taken from Dupré [21]; the signs of c H,v and c D,v have been inverted to correctly reproduce the results from that work. Eigenenergies and eigenvectors based on these parameters are calculated using the program spcat [22].…”

Hyperfine components of all rovibrational quadrupole transitions in the H$_{2}$ and D$_{2}$ molecules

“…The disagreement between recent measurements of rovibrational dipole transitions in the HD molecule [17][18][19] has been attributed to the underlying hyperfine structure of rovibrational states, which were recently studied by Diouf et al [37]. Theoretical studies of the hyperfine components of rovibrational dipole lines in HD were reported [38][39][40] but no such a study concerning quadrupole transitions in H 2 or D 2 was performed.…”