Hyperfine structure of molecular hydrogen

Accurate experimental studies of rovibrational transitions in the ground electronic state of molecular hydrogen isotopologues provide a stringent test of quantum electrodynamics for molecules and can be used to put constraints on hypothetical beyond-Standard-Model interactions. As the accuracy of both theoretical and experimental data surpasses the MHz level, the influence of the underlying hyperfine structure, originating from the interactions involving the nuclear spin or electric quadrupole moment of the deuteron, is necessary to consider in the experimental analysis.

Here, we analyze the leading hyperfine interactions in the six molecular isotopologues of hydrogen: H₂, HD, D₂, HT, DT and T₂. We present the calculated coupling constants: spin-rotation, spin-spin dipole and, in the case of deuterium-bearing species, the electric quadrupole coupling constants for all bound states in the ground electronic state of the six isotopologues. We provide a list of positions and intensities of 1 503 057 hyperfine components of 86 015 rovibrational electric dipole and quadrupole transitions and we discuss the influence of hyperfine splittings on the Doppler-limited spectra.