Excited States ofXe128

Gamma rays accompanying the decay of 25-min ${}_{}{}^{128}{}_{}{}^{}\mathrm{I}$ and 3-min ${}_{}{}^{128}{}_{}{}^{}\mathrm{Cs}$ have been studied with 8-cc and 30-cc Ge(Li) spectrometers. Coincidences between $\gamma$ rays were studied using two 7.6-cm×7.6-cm NaI(Tl) scintillators. In the decay of ${}_{}{}^{128}{}_{}{}^{}\mathrm{I}$, $\gamma$ rays of the following energies were observed (relative intensities in parentheses): 443.3 (100.0), 526.4 (9.9), 743.3 (1.0), 969.7 (2.7), and 1139.9 (0.08) keV. In the decay of ${}_{}{}^{128}{}_{}{}^{}\mathrm{Cs}$, $\gamma$ rays of the following energies were observed (relative intensities in parentheses): 443.0 (100.0), 511.1 (414.0), 526.5 (7.3), 613.5 (0.93), 969.5 (1.6), 1030.8 (0.61), 1139.9 (4.0), 1304.9 (0.47), 1514.2 (0.14), 1631.0 (0.36), 1685.9 (0.32), 1981.9 (0.11), 2041.8 (0.074), 2157.2 (0.62), 2193.0 (0.13), 2277.8 (0.040), 2365.2 (0.15), 2398.2 (0.052), 2419.9 (0.082), 2592.4 (0.011), 2840.5 (0.011), and 2862.2 (0.016) keV. A level scheme for ${}_{}{}^{128}{}_{}{}^{}\mathrm{Xe}$ has been constructed with levels at 443.2 ($2^{+}$), 969.6 ($2^{+}$), 1583.1 ($0^{+}$,$1^{+}$,$2^{+}$), 2275.2, 2484.3, 2600.5, 2841.1, and 2862.8 keV. The most important result of these studies is that no evidence has been found for the existence of a $0^{+}$ member of a possible two-phonon vibrational triplet.