Doppler-free optogalvanic spectrum of He2 b 3Πg–f 3Δu transition

Abstract

Doppler-Free Lamb dip and intermodulated spectra of He2 b 3Πg–f 3Δu transition have been observed by the technique of optogalvanic spectroscopy. The analysis of the triplet splittings of rotational lines yielded the values of spin-orbit (A), spin–spin (λζ and λ⊥⊥) and spin-orbit (γ) coupling constants of AΠ=−6.753±0.26, λζ=3.069±0.37, λ⊥⊥=−4.480±0.03, γ=−0.009±0.02 GHz for the b 3Πg state, and AΔ=−0.073±0.10, λζ=0276±0.27, and γ=0.016±0.03 GHz for the f 3Δu state. The Λ-type doubling in the b 3Πg state was found negligible. The derived values for the b 3Πg state are compared with those for the H2 c 3Πu state which has the optical electron in the same 2pπ orbital as He2 b 3Πg state, and the departure of the electron configuration in the He2 b 4Πg state from the united atom orbital (UAO) is discussed.