Isomeric Cross Section Ratios in Alpha-Particle Reactions

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Isomeric cross section ratios for reactions Mn^<55>(α, n)Co,^<58m, g>Fe^<56>(α, pn) Co^<58m, g> and Rb^<85>(α, 2n)Y^<87m, g> were measured 'by the activation method using a stacked-foil technique. The experimental results of the energy dependence of σ_m/σ_g for Mn^<55>(α, n)Co,^<58m, g> reaction were compared with the calculation using the square-well potential with the interaction radius parameter of r_0 =1.7 fermi and the energy level density parameter of α = 2 MeV^<-1> in Fermi gas model. From the comparison, it seems that as the spin level density parameter either a constant value between σ=3 to σ =4 or the value dependent on nuclear temperature corresponding to 2σ^2 = 14.4T = fits comparatively well in experimental results. However, the experimental result on this reaction shows that the σ_m/σ_g reaches a maximum value at about 25 MeV and then decrease. This behavior may be interpreted by a mechanism of direct interaction. The energy dependence ofσ_m/σ_g for Fe^<56>(α, pn)Co^<58m>, g> reaction qualitatively indicates that the reaction advances through the compound nucleus formation process, contrary to the results for Co^<59>(p, pn) Co^<58m> reaction measured by Meadows et al. in which the same compound nucleus is formed.
社団法人日本物理学会の論文
1962-09-05