Cavity-enhanced absorption and dispersion spectroscopy of the 1238-nm line of H2

Doppler-broadened absorption and dispersion spectra of the Q(1) line in the first overtone band of H2 2 were recorded together with a comb-locked cavity-enhanced spectroscopy instrument. On the basis of the HartmannTran profile, the absorption and dispersion spectra were fitted independently, resulting in two consistent sets of line profile parameters. The intensities obtained by the two methods reached an accuracy below 0.1%, and agree well with the theoretical results. This work not only provides a test of high-level quantum chemistry calculations of the simplest neutral molecule, but also demonstrates the potential for SI-traceable high-precision molecular density measurements based on laser spectroscopy.