Fermi-contact hyperfine interaction and the electron spin g factor in H2 d(3p) 3Πu

Abstract

Microwave optical magnetic resonance induced by electrons (MOMRIE) experiments have been continued on the d(3p) ³Π_u states of ortho‐ and para‐H₂. Transitions that would at the high magnetic field limit be forbidden have been observed at low field (∼ 2 kG). Four such transitions in ortho‐H₂ and two in para‐H₂ have been accurately measured. Previously MOMRIE transitions within these states of H₂ had been observed in the 12–15 kG range where selection rules permit only transitions which are insensitive to the electron spin g factor g_s and the Fermi‐contact hyperfine interaction a_F. The newly observed transitions are sensitive to these parameters and when combined with previous high field data determine g_s in the ν = 0–3 vibrational levels of ortho‐ and para‐H₂ and a_F in the ν = 0–3 vibrational levels of ortho‐H₂. The values of a_F are comparable to those for the c(2p) ³Π_u state of H₂ and the ${\mathrm{X\hspace{0.17em}}}^2{\Sigma }_g^{+}$ state of ${\mathrm{H}}_2^{+}$ , but interestingly (for a given ν) are larger than either value. The values of g_s are found to be close to the free electron spin g factor for all the measured vibrational levels of ortho‐ and para‐H₂. However, they show a slight deviation to the high side of the free electron value, comparable to the experimental error.