Coulomb Excitation of Levels inSe77

An investigation has been made of the gamma rays which de-excite levels of ${\mathrm{Se}}^{77}$ that have been Coulomb excited by means of variable-energy alpha particles (2.1 to 8.0 Mev). The energies (in kev), spins and parities, and $B{\mathrm{}\left(E2\mathrm{}\right)\mathrm{}}_{\mathrm{ex}}\text{'}\mathrm{s}$ (in units of $e^2$ ${\mathrm{cm}}^4$×${10}^{-50\mathrm{}}$) found for the levels are: 242±2, $\frac{3}{2}-$, and 18.2±1.6; 248±5, $\frac{5}{2}-$, and 0.37±0.09; 440±4, $\frac{5}{2}-$, and 25.9±1.7; and 515±8, $\frac{3}{2}-$, and 1.0±0.2. New evidence for the two close-lying levels at 242 and 248 kev has been provided by coincidence studies. A comparison of the $B{\mathrm{}\left(E2\mathrm{}\right)\mathrm{}}_{\mathrm{ex}}\text{'}\mathrm{s}$ to the $B{\mathrm{}\left(E2\mathrm{}\right)\mathrm{}}_{\mathrm{sp}}$ suggests that the 242- and 440-kev levels result from collective excitations of the ground-state configuration, and that the 248- and 515-kev levels result from changes in the ground-state configuration. Besides the ground-state transitions from these Coulomb-excited levels, gamma rays with energies of 87, 161, 203, and 283 kev were observed. Excitation curves of the 87- and 161-kev transitions indicate that they cascade from the 248-kev level. From the measurements of the gamma-ray angular distributions, values for ${\left(\frac{E2\mathrm{}}{M1\mathrm{}}\right)}^{\frac{1}{2}}$ of 0.18±0.03 and 0.05±0.03 were obtained, respectively, for the 242-kev gamma ray and for the 203-kev gamma ray, which originates at the 440-kev level.