Transition strengths and new band structures in odd-odd {sup 78}Rb

High-spin states in {sup 78}Rb were studied using the {sup 54}Fe({sup 28}Si,3{ital pn}) reaction at 120 MeV and the {sup 58}Ni({sup 23}Na,2{ital pn}) reaction at 65 and 70 MeV. Prompt and delayed {gamma}-{gamma} coincidences were measured using the Pitt-FSU detector array. Results from these experiments have led to new levels partly grouped into new bands, new spin-parity assignments, and a rearrangement of the low-lying portion of the level scheme. States were observed up to (19{sup +}) and (15{sup {minus}}) in the lowest energy positive- and negative-parity bands. Spin assignments were based on both directional correlation of oriented nuclei ratios and angular distributions. For some low-lying levels parity assignments were supported by a measurement of the linear polarizations of {gamma} rays. Lifetimes were determined using the Doppler-shift attenuation method and direct timing. A reversal of signature splitting was observed in the yrast band at the 10{sup +} state. Large alternations were seen in the {ital B}({ital M}1) strengths in the yrast band, while the {ital B}({ital E}2) values in the two most strongly populated bands show a considerable collective enhancement. {copyright} {ital 1996 The American Physical Society.}