Ro-vibrational population distribution in the ground state of hydrogen isotopologues in LHD peripheral plasmas deduced from emission spectroscopy

Highlights: • Ro-vibrational population distributions of H2 and D2 in LHD peripheral plasmas were estimated from Fulcher-α Q-branch emission spectra. • Ro-vibrational populations up to v = 2 and n = 11 of H2 and up to v = 3 and n = 14 of D2 in the ground state is deduced for the first time. • The rotational population of every vibrational state follows two-temperature Boltzmann distribution. Wide wavelength range with high-resolution emission spectroscopy was applied to LHD peripheral plasmas. All measured Fulcher-a band Q-branches spectra (600–630 nm) were measured with a single shot exposure time of 100–200 ms for all investigated discharges. Ro-vibrational populations up to v = 2 and N = 11 for H₂ and up to v = 3 and N = 14 for D₂ in the 3p³Π_u state were estimated, where v and N are vibrational and rotational quantum numbers, respectively. It was found that the rotational population of every vibrational state follows two-temperature Boltzmann distribution. From the calculation with a coronal model, ro-vibrational populations distribution up to such high N quantum numbers in the ground state are deduced.