HYPERFINE STRUCTURES OF THE LI-7(2) B(3)PI(U), 2(3)PI(G), AND 3(3)PI(G) STATES - CONTINUOUS-WAVE PERTURBATION FACILITATED OPTICAL-OPTICAL DOUBLE-RESONANCE SPECTROSCOPY

The hyperfine structure of the b 3 Pi(u), 2 (3) Pi(g), and 3 3 Pi(g) s tates of Li-7(2) has been studied by continuous wave perturbation faci litated optical-optical double resonance fluorescence excitation spect roscopy. The b 3 Pi(u) state has case b(beta J) coupling scheme. The h yperfine splittings of the two perturbed b (3) Pi(u) v=19, N=10, J=11e , s, F-1 and v=19, N=5, J=4e, a, F-3 levels were resolved and hyperfin e constants determined to be +9.90 MHz and -20.94 MHz, respectively. F ermi contact is the main source of the hyperfine interaction and b(F)( b (3) Pi(u))=+107 MHz has been obtained. The coupling schemes of diffe rent 2 (3) Pi(g) levels are different: N=4, 6 levels observed from the b (3) Pi(u) v'=19, N'=5, J'=4e, a, F-3 intermediate level and the N=1 0 levels observed via the b (3) Pi(u) v'=19, N'=10, J'=11e, s, F-1 int ermediate level have case b(beta J) coupling; the N=5 levels observed via the b (3) Pi(u) v'=19, N'=5, J'=4e, a, F-3 intermediate level and the N=9, 11 levels observed from the b (3) Pi(u) v'=19, N'=10, J'=11e, s, F-1 intermediate level are closer to case b(beta S) coupling. Hype rfine constants have been calculated and the Fermi contact constant, b (F)(2(3) Pi(g),)=60 MHz is obtained. The 3 (3) Pi(g), State is a Rydbe rg state and has case b(beta S), coupling with b(F)(3 (3) Pi(g))approx imate to 100 MHz. (C) 1996 American Institute of Physics.