Search For Isospin Effects On The Level Density Of Nuclei Involved In The Decay Of Eu-139

Evaporative proton and alpha particle energy spectra and angular distributions have been measured in the decay of the compound nucleus Eu-139 produced at an excitation energy of 90 MeV by the S-32 + Ag-107 reaction. In-plane and out-of-plane angular distributions and energy spectra of alpha particles have been compared with theoretical calculations performed using the statistical Montecarlo code Lilita. Three expressions for the level density parameter have been used: a) without isospin dependence b) with N-Z isospin dependence and c) with Z-Zo isospin dependence, based on the distance of the nucleus from the valley of stability. The predictions by the Z-Zo prescription fail to reproduce the data. Isospin independent and N-Z dependence reasonably well reproduce the data.