Progress report on the measurements of pressure-broadening of HD rotational transitions for Jovian atmospheres

We have conducted a laboratory study to measure pressure-broadened line shape parameters of hydrogen deuteride (HD) for pure rotational transitions, R(0)-R(3), in the 85-360 cm^-1 region in support of various NASA space telescope missions, such as ISO, Spitzer, Herschel/PACS, upcoming JWST, and future FIR space telescopes (e.g., Origin). D/H ratios are crucial indicators of planetary formation and evolution, and they are most directly obtained from HD and H₂ abundance measurements. The accuracy of spectroscopic parameters has a direct impact on uncertainties in the derived abundances. In particular, the collisional broadening coefficients of the pure rotational transitions of HD listed in the HITRAN 2016 database seem to be off by a factor of about five compared with the values reported in previous laboratory studies. Since pressure broadening parameters are substantially coupled to line intensities, all the spectroscopic parameters (such as position, intensity, linewidth, and pressure shift) are best retrieved simultaneously. The reported work has achieved simultaneous retrieval using the multispectrum fitting package LABFIT. We have performed new high resolution (e.g., 0.0007 cm^-1) spectra using the AILES beamline at Synchrotron Soleil, France, source and a Brucker 125 HR Fourier transform spectrometer. The measurements cover the temperature ranges of 100–296 K. The observed spectra have been analyzed using a state-of-the-art multi-spectrum fitting algorithm adopting non-Voigt line shape profiles, so that we have determined their spectroscopic line parameters and their temperature dependences, including the collisional narrowing coefficients. We will present new results and compare them with previous work and the parameters listed in HITRAN. (Note: Government sponsorship has been acknowledged.)