Level Crossing Determination ofτ(P11)andgJ(P13in Zinc and the hfs ofZn65andZn67

Optical detection of level crossing in the $\mathrm{}\left(4s4p\right)\mathrm{}{}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$ state of stable ${\mathrm{Zn}}^{67}$ and of 245-day ${\mathrm{Zn}}^{65}$, using the intercombination line at 3076 Å, has resulted in a precise determination of the ratios of the dipole and quadrupole hyperfine coupling constants in each of the isotopes to the Landé $g_J$ factor of this state. Using these results and the values of the dipole coupling constant for each isotope, as determined from double resonance experiments, we obtain the following values for the atomic $g$ factor and "isolated" quadrupole interaction constants: ${\mathrm{Zn}}^{67}$: $g_J=1.501006\mathrm{}\left(8\right)\mathrm{}$ and $B=-18.770\mathrm{}\left(12\right)\mathrm{}$ Mc/sec, ${\mathrm{Zn}}^{65}$: $g_J=1.500984\mathrm{}\left(20\right)\mathrm{}$ and $B=2.867\mathrm{}\left(12\right)\mathrm{}$ Mc/sec. The results for $B$ agree with those obtained from double resonance, indicating the adequacy of our treatment of the second-order fine-structure corrections. The lifetime ($\tau$) of the $\mathrm{}\left(4s4p\right)\mathrm{}{}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$ state of Zn has been determined to be $\tau =(1.38\mathrm{}\pm 0.05)\times {10}^{-9\mathrm{}}$ sec through the observation of the zero-field level crossing (Hanle effect), using the resonance line at 2138 Å. These latter experiments were performed with natural zinc (96% even isotopes), and included the quantitative determination of coherence narrowing.