Excited states in {sup 52}Fe and the origin of the yrast trap at I{sup {pi}}=12{sup +}

Excited states in {sup 52}Fe have been studied up to spin 10{h_bar} in the reaction {sup 28}Si+{sup 28}Si at 115 MeV beam energy by using in-beam {gamma}-ray spectroscopy methods at the GASP array. The excitation energy of the yrast 10{sup +} state is 7.381 MeV, almost 0.5 MeV above the well known {beta}{sup +}-decaying yrast 12{sup +} state. Experimental upper limits for the B(E4) transition probabilities from the 12{sup +} isomer to the 8{sub 1}{sup +} and 8{sub 2}{sup +} states have been determined. The mean lifetimes of five excited states have been measured by using the Doppler shift attenuation method. Complete diagonalizations in the pf major shell lead to very good agreement with the experimental level scheme and transition probabilities. The lifetime, log ft value, branching ratios, and B(E4) values are calculated for the 12{sup +} isomer. The positive parity states are also interpreted in terms of a Nilsson projected method. The structure of the yrast levels of {sup 52}Fe is compared with those of its cross conjugate {sup 44}Ti. {copyright} {ital 1998} {ital The American Physical Society}