We have used the atomic-beam magnetic-resonance technique to improve and extend the measurements of Title and Smith on the hyperfine structure of the (6p ) $3/2 ground state of Bi (I= 2 ) . We measured the three zero-field hyperfine intervals and computed the octupole interaction constant. Our experimental results are P~(&= 5 &= 6) = 2884.666(2), &2(&=4 -+=5) =2171. 419(2), and v3(F =3-&=4)=1584.502(2) MHz. From these values, we obtain for the hyperfine-interaction constants, corrected for the pseudo-octupole interactions due to perturbation by neighboring fine-structure levels A = -446.937 (1), B= -305.067(2), and C = 0.0183(1) MHz. The assigned errors include only the experimental errors in the measurement of the three hyperfine intervals, and no estimate of the errors in the theoretical corrections has been made. We have also corrected the data of Lurio and Landman for the (6p ) P3~2 meta-3 2 stable state of bismuth for these octupolelike interactions and have deduced a fairly consistent value for the one-electron octupole-interaction constant. From the average value of the octupole-interaction constant c3~2--0.0206 MHz we find that the nuclear magnetic octupole moment is 0.0086@&b. This value is compared with the prediction of the shell model.

In a hyperfine-optical-pumping experiment we employed the Franzen transient method to determine the total spin-exchange cross sections for Rb 87 -Rb 87 and Rb 87 -Cs 133 collisions at 78°C. Values determined in this way were: (r(Rb 87 -Rb 87 )=(1.9±0.2)X10-14 cm 2 and

The hyperfine structure and isotope shift of five radioactive isotopes of thallium have been measured spectroscopically. Thallium-199 (7.4 hr) and thallium-200 (27 hr) were produced by alpha bombardment of gold; thallium-201 (3 day), thallium-202 (12 day), and thallium-204 (4 year) were produced by deuteron bombardment of liquid mercury. The isotopes were excited in electrodeless-discharge lamps. Approximately 0.001 ug of radio-thallium was used in the lamps. The hfs splittings and isotope shifts in the 6 2 P, 62Pg, and 7 2 Si states were obtained by using a 10-in. plane diffraction grating in autocollimation in a 40-ft mirror monochromator. Previously measured values of the nuclear spins of the odd-even isotopes have been verified. Nuclear magnetic moments or upper limits on the moments have been calculated by comparison of the hyperfine splittings of the radioactive isotopes with the known splittings and moments of the stable thallium isotopes. A definite dependence of the relative isotope shifts on neutron number was observed.

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