Using the experimental data on total { \it S}=1 transition cross-sections \, for $^4$He$(\gamma,p)$$^3$H and $^4$He$(\gamma,n)$$^3$He reactions as the base, the paper describes the possibility of measuring the probability of { \it P}-states in the $^4$He nucleus. The { \it S}=1 transitions may originate from $^3P_0$ states of the nucleus, or be the result of the spin-flip of the final-state particle system from $^1S_0$, or $^5D_0$ states of the $^4$He nucleus, and also as a result of the secondary effects. The analysis of the experimental data has suggested the conclusion that within the statistical error the ratio of the { \it S}=1 transition cross-sections in the collinear geometry to reaction cross-sections at polar nucleon-exit angle $\theta_N$=$90^{ \circ}$ $\nu_p$ and $\nu_n$ in the photon energy range 22$\le$E$_{ \gamma}$$\le$100 MeV is independent of the photon energy. This is in agreement with the assumption that the { \it S}=1 transitions can originate from $^3P_0$ states of the $^4$He nucleus. Average values of magnitude $\nu_p$ and $\nu_n$ in the mentioned photon energy range are calculated $\nu_p$=0.01$\pm$0.002 and $\nu_n$=0.015$\pm$0.003. The errors are statistical only.
Categories: nucl-ex nucl-th