An interferometric method is used to improve the accuracy of the 7S-7P transition frequencies of three francium isotopes by 1 order of magnitude. The deduced isotope shifts for 209-211Fr confirm the ISOLDE data. The frequency of the D2 transition of 212Fr--the accepted reference for all Fr isotope shifts--is revised, and a significant difference with the ISOLDE value is found. Our results will be a benchmark for the accuracy of the theory of Fr energy levels, a necessary step to investigate fundamental symmetries.
We have measured the hyperfine relaxation time of cesium vapor in the presence of foreign gases. We have therefore been able to measure the diffusion coefficient Do and the cross section 0&&. && of hyperfine relaxation due to the collisions with the foreign gas. The values of Do for He, Ne, Ar, and N2 are 0.204+0. 04, 0. 153+0.014, 0. 134+0.02, and 0.073+0.015 cm2/sec at O'C and 760 Torr, respectively. The cross sections are 2. 80+0.3, 9.27+0. 9, 104+10, and 55. 2+4.4 in units of 10-3 cm for He, Ne, Ar, and N&, respectively. We have also improved on the measurement of the spin-exchange cross section oe obtaining the value (2. 18+0.12) x10~4 cm . We compare the problems arising in the study of hyperfine and Zeeman relaxation and we discuss the results.
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