Measurements of Lowest-S-State Lifetimes of Gallium, Indium, and Thalium

The lifetimes of the gallium $5{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$ state, the indium $6{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$ state, and the thallium $7{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$ state were measured using the zero-field level-crossing (Hanle-effect) technique. The life-times obtained were (6.8±0.3) × ${10}^{-9\mathrm{}}$, (7.0±0.3) × ${10}^{-9\mathrm{}}$, and (7.45±0.2) × ${10}^{-9\mathrm{}}$ sec, respectively. Anomalous contributions to the level-crossing signals, from the wavelength dependence of the exciting light intensity and self-absorption by the fluorescing atomic beam, were investigated in detail.