An Atomic Beam Study of the Hyperfine Structure of the MetastableP322State ofIn115I. The Electric Quadrupole Moment ofIn115

The zero-moment method of atomic beams has been used to investigate the hyperfine structure of the metastable ${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ state of ${\mathrm{In}}^{115}$I. Thirteen zero-moment peaks have been observed, and it is found that their behavior is completely described by the equation for the h. f. s. energy levels, $E=\frac{1}{2}aC+bC(C+1\mathrm{})\mathrm{}$, together with a knowledge of the nuclear $g$ factor. $a$ and $b$ are the interval rule and quadrupole interaction constants, respectively; the numerical values are $\frac{b}{a}=(6.432\mathrm{}\pm 0.04)\times {10}^{-3\mathrm{}}$; $a=(8.10\mathrm{}\pm 0.10)\times {10}^{-3\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$; $b=(0.0521\mathrm{}\pm 0.0009)\times {10}^{-3\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$. From this the total h. f. s. separation is (0.1184±0.0015) ${\mathrm{cm}}^{-1\mathrm{}}$ and the quadrupole moment of ${\mathrm{In}}^{115}$ is 0.84×${10}^{-24\mathrm{}}$ ${\mathrm{cm}}^2$. The nuclear spin is verified to be 9/2. If there is an additional term $c(C^3+4\mathrm{}{C}^2+\frac{4}{5C})$ in the h. f. s. energy level equation, as suggested by Tolansky in the case of iodine, an upper limit of 5×${10}^{-6\mathrm{}}$ may be set on $\frac{c}{a}$.