Fine structure and Zeeman effect in the b(1)3Πu state of 6Li2 by Doppler-free polarization spectroscopy

Abstract

High resolution laser spectroscopy of Cs2. II. Dopplerfree polarization spectroscopy of the C 1Π u ←X 1Σ+ g system The fine structure of the b(1)3TIu state of the lithium dimer was observed for the first time and studied using Doppler-free polarization spectroscopy. The triplet state was accessed by excitation of the A I~u"" {t/; = 2,J =33) -be 1 )3TIu Cv = 9,N = 32,F I ,e) spin-orbit perturbed levels. The remaining two fine structure levels were excited by using the Zeeman interaction to mix levels of different J. Two polarization geometries, 17" pump and cr pump, were used to study separately different groups of M J levels in magnetic fields up to 3 kG. An irreducible tensor derivation of the fine structure and Zeeman Hamiltonian matrix in Hund's case (b) symmetrized basis functions was carried out and used to determine the perturbation parameters and the spin-spin and spin-rotation fine structure constants by a fit to the Zeeman splitting pattern. The spin-orbit contribution to the fine structure is too small in the high J states to be found accurately. The electronic spin-orbit coupling perturbation for the interaction between the singlet and triplet states was also determined to be Hel(A_b) = 0.1172 ± 0.0008 cm -I.In the present study the A I~t (v =2,J = 33) .-b(1)3TIu (v = 9,N = 32), fine structure states were excited from X I~g+ (v = O,J = 34 and J = 32) with a single 928

Hyperfine structures of the 7Li2 b3Πu, 23Πg, and 33Πg states: Continuous wave perturbation facilitated optical–optical double resonance spectroscopy

“…Because of the extremely small size of the spin-orbit interaction matrix element, 15,16,29 only those A 1 ⌺ u ϩ and b 3 ⌸ u levels which satisfy the ⌬Jϭ0, e↔e selection rules, have larger vibrational overlap, and happen to be very close ͑within the Doppler profile͒ can have significant mixing. 15,16,29 Thus even with single mode, frequency stabilized lasers ͑1 MHz linewidth͒ it is impossible to excite selectively only a predominant A 1 ⌺ u ϩ or a predominant b 3 ⌸ u perturbation component.…”

“…15,16,29 Thus even with single mode, frequency stabilized lasers ͑1 MHz linewidth͒ it is impossible to excite selectively only a predominant A 1 ⌺ u ϩ or a predominant b 3 ⌸ u perturbation component. Fine and hyperfine splittings of the b 3 ⌸ u levels are even smaller.…”

“…29,30 While the A 1 ⌺ u ϩ ϳb 3 ⌸ u perturbations of Na 2 and K 2 were detected in the early 1900s, the A 1 ⌺ u ϩ ϳb 3 ⌸ u perturbation of Li 2 was not detected until 1985. 16 Preuss and Baumgartner 16 systematically examined more than 2000 individual rotational-vibrational levels of the A 1 ⌺ u ϩ state of 6 Li 2 , 6 Li 7 Li, and 7 Li 2 , and found that 46 levels have an anomalous lifetime: 44 of the 46 levels have a shortened lifetime while two 6 Li 2 A 1 ⌺ u ϩ levels ͑vϭ2, Jϭ33 and vϭ3, Jϭ51͒ have a longer lifetime.…”

“…Jeng et al, using sub-Doppler polarization Zeeman spectroscopy, resolved the fine structure of the 6 Li 2 b 3 ⌸ u vϭ9, Nϭ32 level and obtained spin-spin, spin-rotation, and spin-orbit parameters. 29,30 Later, three pairs of A 1 ⌺ u ϩ ϳb 3 ⌸ u mixed levels of 7 Li 2 have been identified: 21 …”

The Perturbation between the G1Π and 21Δ States of 7Li2

“…(2), the perturbation of the 1 ⌺ g ϩ states was considered to be the source of the ⌳-doubling of the G 1 ⌸ g state. Since triplet ϳ singlet perturbations are very weak in Li 2 (8,9), the large deviation of the f-parity levels of the G 1 ⌸ g state must be due to perturbations from the nearby 1 ⌸ g or/and 1 ⌬ g states.…”