Electromagnetic transitions in 51Mn

Abstract

The nuclear structure of 51 25Mn was studied by γ-ray spectroscopy in the 54Fe(p, α) 51 Mn reaction ( E p = 9.0–13.2 MeV) and the 14N+ 39K, 16O+ 40Ca and 14N+ 40Ca fusion-evaporation reactions ( E beam = 36 MeV). In the 54Fe(p, αγ) 51Mn reaction γ-rays were detected in coincidence with α-particles emitted near 180°; mean lifetimes and γ-ray mixing and branching ratios were deduced from Doppler shift attenuation and α-γ angular correlation measurements, respectively. Definite spin assignments are: 237 and 2416 keV, J π = 7 2 − ; 1140 keV, 9 2 −; 1488 keV, 11 2 −; 1825 and 2140 keV, 3 2 −. The results for other states below 3 MeV are consistent with the existence of rotational bands (/kh 2/2/OI/t~ 95 keV) built on the ( 3 2 +) 1817 keV and 1 2 + 2276 keV hole states. The various measurements together with an earlier value for the lifetime of the first-excited state determine unambiguously the B(M1) and B(E2) values for all of the decay branches of the 7 2 −, 9 2 − and 11 2 − lowest three excited states. From the γ-singles and γ-γ coincidence observations with fusion-evaporation reactions, the yrast cascade proceeds through these three states and higher states at 2957, 3250,3680 and 4139 keV which are suggested to have J π = 13 2 − , 15 2 −, 15 2 − and 19 2 −, respectively. The various experimental results for the 5 2 − → ( 19 2 −) yrast states are in good overall agreement with shell-model calculations in the (f 7 2 ∗ space.