Hole-vibration coupling in 115In

Abstract

The collective states of 115In have been studied by Coulomb excitation with 16O and 12C ions, and by inelastic scattering of 12 MeV deuterons. In both experiments the excitation strength is strongly concentrated on a group of levels in the region of 900 to 1500 keV. A number of additional levels were observed in the (d, d')reaction. Several strong M1 transitions between the excited levels were observed in theγ-decay spectra. The levels directly excited by Coulomb excitation (in keV), their B( E2↑) transition probabilities (in 10 −2 e 2 · b 2), and the inferred spin-parity assignments are: 941.7(0.27) 5 2 + , 1078.2(2.2) 5 2 + , 1133.1(10.0) 11 2 + , 1290.6(5.0) 13 2 + , 1449.4(1.24) 9 2 + , 1463.7(1.24) 7 2 + , and 1486.6(0.60) 9 2 + . Large Doppler broadenings were observed in the decays of the 1133 and 1464 keV levels, indicating predominantly M1 downward transitions. A calculation of the 115In spectrum involving strong coupling of a 1g 9 2 proton hole to the vibrational states of 116Sn was performed. The results are in good agreement with the level positions, B( E2) values, and ground state quadrupole moment, and with the relative spectroscopic factors observed in the 116Sn(d, 3He) 115In reaction. The M1 transition strengths are also predicted reasonably well. No support was found for the existence of a proposed rotational band in 115In.