CARS spectroscopy of the $(v=0\to 1)$ band in ${T_2}_{}$

Molecular hydrogen is a benchmark system for bound state quantum calculation and tests of quantum electrodynamical effects. While spectroscopic measurements on the stable species have progressively improved over the years, high-resolution studies on the radioactive isotopologues $T_2$, $HT$ and $DT$ have been limited. Here we present an accurate determination of T₂ $Q(J=0\text{--}5)$ transition energies in the fundamental vibrational band of the ground electronic state, by means of high-resolution coherent anti-Stokes Raman spectroscopy. With the present experimental uncertainty of $0.02{cm}^{-1}$, which is a fivefold improvement over previous measurements, agreement with the latest theoretical calculations is demonstrated. (paper)