The lifetime of the first excited ${}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$ state of zinc, calcium, and strontium has been measured by the zero-field level-crossing technique. The results are: zinc $\tau \left({}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}\right)=1.41\mathrm{}\pm 0.04\times {10}^{-9\mathrm{}}$ sec, calcium $\tau \left({}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}\right)=4.48\mathrm{}\pm 0.15\times {10}^{-9\mathrm{}}$ sec, and strontium $\tau \left({}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}\right)=4.97\mathrm{}\pm 0.15\times {10}^{-9\mathrm{}}$ sec. The results are compared to earlier experimental results and also to theoretical predictions. It is found that our results are in excellent agreement with the Bates and Damgaard Coulomb approximation method for estimating the oscillator strengths.

• Received 9 January 1964

DOI:https://doi.org/10.1103/PhysRev.134.A1198