Singlet–triplet anticrossings between the doubly excited 3 1K state and the g (3d) 3Σ+g state of H2

International audienceThe 3 1K, v=1 level of H2 has recently been interpreted as an adiabatic mixture of vibronic levels of the EF 1Sigma s+ and the GK 1Sigma g+ double minimum states, with currently undetermined nonadiabatic corrections. Anticrossing spectra, which are sensitive to these state mixings, have been observed for the 3 1K, v=1, N level and the (3d) 3Sigma g +, v=1, N level of ortho-H2 for the rotational levels N=1 and 3. Linewidths, which are determined by either the singlet-triplet Fermi-contact hyperfine interaction or the spin-orbit interaction, as well as magnetic g values, help provide a detailed description of the 3 1K state. Measured singlet-triplet zero field separations are combined with previously published values to provide the best available value for the energy T 0(a 3Sigma) of the lowest triplet level (a 3Sigma, v=0, N=0) with respect to the ground state, 95076.36±0.20 cm-1