Nonresonant multiphoton excitation spectra of atomic Li-7

The nonresonant multiphoton laser-induced fluorescence excitation spectrum of isotopically purified Li-7 was obtained with a tunable, pulsed, nanoseco nd laser scanned between 13 600 and 14 500 cm(-1). The measured Rydberg ser ies include n P-2 <-- 2(2)S, n F-2 <-- 2(2)S, n P-2 <-- 2(2)P, and n F-2 <- -2(2)P, and term values up to 14 P-2 and 28 F-2 were determined. Features d ue to the ac Stark effect become prominent for the high Rydberg states, but can be eliminated by using circular instead of plane-polarized radiation. Quantum defect values for the n P-2, n D-2, and n F-2 levels were determine d. Those for the n F-2 states cover a range of principal quantum numbers no t previously investigated.