Knowledge Bank

The hyperfine structure of the two resonance lines of gallium I, in the visible, $42P1/2-5S1/2$, 4033A, and $42P3/2-5S1/2$, 4172A has been investigated by means of the absorption of a multiple atomic beam of high collimation, observed with a double Fabry-Perot etalc. The combined Doppler and instrumental width was approximately 5 mK. In the line 4033 A, the components of the two isotopes $Ga69$ and $Ga71$ were very well resolved, their separation being about 4 times their line width, and since 68 independent measurements were made, the probable error in the positions of the hfs components was reduced to approximately 0.1 mK. From these measurements are derived: -- the hfs intervals of the terms $42P1/2$ and $5S1/2$ for $Ga69$ and for $Ga71$, the ratio of the magnetic moments of the nuclei given by each of these terms and the isotope shift for the line. The line 4172 was less well resolved, due to the smaller separations of the components of the two isotopes, and they were mostly observed as blends; but the structure of the level $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}P3/2$ can be derived with an accuracy of the order of 2 mK and an approximate value can be found for quadrupole moments of the nuclei.