MEASUREMENTS OF THE RESONANCE LINES OF LI-6 AND LI-7 BY DOPPLER-FREE FREQUENCY-MODULATION SPECTROSCOPY

Using Doppler-free frequency-modulation spectroscopy, we have measured most of the hyperfine components and the centers of gravity of the D-1 line of Li-7 and the D-2 line of Li-6. By using previously measured fine- and hyperfine-structure splittings, we have also determined centers of gravity for the D-2 line of Li-7 and the D-1 line of Li-6. Our present results are more accurate than previously reported values by a factor of more than 100. The wave numbers are Li-7 D-2: 14 903.983 468 (14) cm(-1); Li-7 D-1: 14 903.648 130 (14) cm(-1); Li-6 D-2: 14 903.632 116(18) cm(-1); Li-6 D-1: 14 903.296 792 (23) cm(-1). Values for the isotope shifts of the resonance lines of 0.351 338 (21) cm(-1) for the D-1 line and 0.351 352 (15) cm(-1) for the D-2 line have been derived. All uncertainties represent a 95% level of confidence.