Study on the α decay of highly excited states of deformed nuclei by means of (n, α) reactions

The (n, α) reaction on the 151Eu, sup(155,157)Gd, sup(171)Yb, sup(177)Hf and sup(187,189)Os deformed target nuclei was studied using the resonance neutrons. The measurements were carried out by the time-of-flight technique. The magnitudes of the total α-widths have been determined by the relative method using 147Sm resonance at E0=3.42 eV with the widths of GITAsub(α)=(1.8+-0.2) μeV, GITAsub(n)=(1.31+-0.034) meV, GITA=(66+-3) meV as a reference resonance. The lifetimes tausub(α) respective to the α-decay are estimated. For the nuclei studied 0.01 < tausub(α) < 1 μs, while for the spherical nUclei studied earlier 0.001 < tausub(α) < 10 ns. The neutron resonances may be considered as a quasistable ones, and the α-decay of the high-exited states may be treated by analogy with the α-decay of ground states. The mean ratios of the experimentally measured total α-widths to the theoretically calculated ones are equal to Ksub(def)=3.2+-1.5 and Ksub(spher)=1.2+-0.2 for the deformed (150 < A < 478) and the spherical (60 < A < 150) nuclei respectively. These ratios give indirect estimation of the influence of nonsphericity of nuclei on the probabilities of α-decays of high-exited states