Decay ofSn109and the Level Structure ofIn109

The excited levels of ${\mathrm{In}}^{109}$ have been investigated from the decay of ${\mathrm{Sn}}^{109}$ with high-resolution Ge(Li) and Si(Li) detectors and with standard scintillation counters. ${\mathrm{Sn}}^{109}$ was produced by the ($\alpha , n$) reaction on enriched ${\mathrm{Cd}}^{106}$. $\gamma$ rays of the following energies (in keV) and intensities have been assigned to the decay of ${\mathrm{Sn}}^{109}$: 119(<1), 223(∼2), 330.5(17.1), 335(4.5), 345(3), 390(6.4), 437(4.6), 442(5), 526(5.5), 609(2), 649.5(68), 725(1.5), 790(∼2), 839(0.7), 843(0.6), 872(∼1), 950(<1), 1028(17.8), 1037(12.7), 1098(100), 1120(9.1), 1221(0.7), 1321 (37.4), 1443(1.8), 1465(33.8), 1488(17.8), 1497(∼1), 1574(18.8), 1618 and 1622(2.5), 1688(2.0), 1712(1.9), 1729(2.6), 1741(1), 1762(3.5), 1823(1.5), 1841(<1), 1912(15.5), 1930(1.4), 1935(0.3), 1944(3.1), 1952(0.3), 1963(0.1), 1976(0.2), 2053(5.8), 2126(3.6), 2160(2.3), 2193(3.7), 2275 and 2278(1.6), 2349(<1), 2541(7.9), 2595(1.5), 2786(3.9), 2811(0.8), 2860(2.3), 2939(0.27), 3010(0.37), 3033(0.37), 3050(0.97), 3062(0.23), 3074(0.08), 3314(0.22), 3360(0.07), and 3393 (0.35). The use of two Ge(Li) detectors in coincidence studies has revealed the presence of several previously unreported transitions. Based on $\gamma -\gamma$ and $\beta -\gamma$ coincidence results, a consistent level scheme of ${\mathrm{In}}^{109}$ is given. The spin and parity assignments of some of the low excited levels of ${\mathrm{In}}^{109}$ are discussed.