FOURIER-TRANSFORM-SPECTROSCOPY MEASUREMENTS IN THE SPECTRA OF NEUTRAL LITHIUM, LI-6-I AND LI-7-I (LI-I)

The most recent measurements leading to improved Li I energy levels appeared in the late 1950s. Since then, many high- and ultrahigh-precision spectroscopy techniques have been used to measure the fine and hyperfine structures and isotope shifts of this atom. Most previous measurements were made on Li-7. Using high- and low-current hollow cathode sources and Fourier-transform spectrometry, we have made measurements in both Li-7 and Li-6 including nine previously unmeasured infrared lines. Wave-number measurements were obtained on 34 Lines from 1829 to 30 925 cm(-1). The strongest lines have been determined to +/-0.0010 cm(-1). We also measured 22 new isotope shifts, and added specific mass shifts for five levels. The resonance lines at 6707 Angstrom in both isotopes, emitted by low-current, commercial lithium hollow cathode sources, were measured to +/- 0.0005 cm(-1). The energy levels have been recalculated using the new data.