Excited states in 52Fe and the origin of the yrast trap at Iπ=12+

Excited states in Fe-52 have been studied up to spin 10h in the reaction Si-28 + Si-28 at 115 MeV beam energy by using in-beam gamma-ray spectroscopy methods at the GASP array. The excitation energy of the yrast 10(+) state is 7.381 MeV, almost 0.5 MeV above the well known beta(+)-decaying yrast 12(+) state. Experimental upper limits for the B(E4) transition probabilities from the 12(+) isomer to the 8(1)(+) and 8(2)(+) 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+ isomer. The positive parity states are also interpreted in terms of a Nilsson projected method. The structure of the yrast levels of 52Fe is compared with those of its cross conjugate Ti-44. [S0556-2813(98)02610-7].