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It is well known that a finite neutrino mass would provide a backing not only for modern theories of particle physics beyond the standard model, but, in a literal sense, for the whole universe, also. Whereas particle physicists would accept more or less any positive result as a gauge of their theories, the astrophysicists calculate that a mass of the order of 10 eVlc2 (averaged over the three flavors) of the many relic neutrinos from the big bang would mark the turning point from an open to a closed universe. No wonder, therefore, that physicists set out to hunt the neutrino mass by any possible means.

Microwave transitions between the Zeeman split doublet states 22 P 1/2 and 22 P 3/2 of7Li have been measured using the optical double resonance method. The fine structure separation was determined to bev fs=10.053.184(58) MHz. The hyperfine structure was well resolved and led to considerably improved precision of the diagonal coupling constantsa 1/2=45.914(25) MHz,a 3/2=−3.055(14) MHz,b=−0.221(29) MHz. Furthermore, the contact, spin dipolar and orbital magnetic hyperfine constants are evaluated using additional results from level crossing experiments, which are more sensitive on the non-diagonal magnetic hyperfine constanta 3/2,1/2. The results are in good agreement with recent theoretical calculations. The nuclear quadrupole moment is derived fromb to beQ(7Li)=−41(6) mbarn.

The nuclear Zeeman levels of the ground state of Barium (6s21S0, F=I=3/2) were polarized by means of optical pumping with the resonance line (6s21S0−6s 6p1P1, λ=5535 A). The magnetic field was calibrated by means of optical pumping of sodium. The magnetic moments, calculated from the nuclear Hf-Zeeman-transitions at 228 Gauss are μ135=0,83651 (6) μN μ137=0,93573 (6) μN (with diamagnetic correction).

The3 P 1 state of Ca (τ≈0,5 msec) was populated by resonance-absorption of the intercombination line (λ=6572,8 A). The radio-frequency-transitions between the Zeeman-sublevels of the excited state were observed by means of optical double-resonance. Because of the oscillator-strength of the intercombination line being extremely small, a second excitation method, namely with electron impact, was tried. Both methods yielded equivalent results. In order to determine theg J -value of the3 P 1-state the static magnetic field was calibrated by Zeeman-transitions in the ground state of Na, the transitions being detected by optical pumping,g J was found to be 1,50105(7) in agreement with the theoretical value 1,50108.

The nuclear Zeeman levels of the odd isotopes of Ytterbium (171Yb,171 I=1/2;173Yb,173 I=5/2) were polarized in the atomic ground state (6s 2 1 S 0) by means of optical pumping with the resonance line (6s 2 1 S 0 ↔ 6s6p 1 P 1,λ=3988 a). The magnetic moments, calculated from the nuclear Hf-Zeeman transitions in a magnetic field of 228 Gauss are171 Μ I=0.49188 (2)Μ K 173 Μ I=0,67755 (3)Μ K (with diamagnetic correction applied).