Absolute (γ, p0) and (γ, p1) cross sections and angular distributions for the closed-neutron shell nucleusY89

Abstract

Absolute ($\ensuremath{\gamma}, {p}_{0}$) and ($\ensuremath{\gamma}, {p}_{1}$) differential cross sections for $^{89}\mathrm{Y}$ were measured at seven angles in the energy interval between 13 and 24.6 MeV, from which the angular distribution coefficients were deduced by fitting a sum of Legendre polynomials. In these cross sections we observe a number of isolated resonances which can be identified as the isobaric analogs of known $\frac{1}{{2}^{+}}$ and $\frac{3}{{2}^{+}}$ excited states in the $^{89}\mathrm{Sr}$ parent nucleus. The appearance of a maximum around 21 MeV excitation energy in both total cross sections may indicate the existence of the ${T}_{>}$ coherent dipole state. From the angular distribution coefficients in the ($\ensuremath{\gamma}, {p}_{0}$) channel, an upper and lower limit for the $E2$ photon absorption were estimated as being equal to 22% and 6%, respectively, of the total $E2$ energy-weighted sum rule.NUCLEAR REACTIONS $^{89}\mathrm{Y}(\ensuremath{\gamma}, {p}_{0})$, ($\ensuremath{\gamma}, {p}_{1}$), $E=13.0\ensuremath{-}24.6$ MeV, $\ensuremath{\theta}=37\ensuremath{-}143\ifmmode^\circ\else\textdegree\fi{}$; measured $\ensuremath{\sigma}(E; \ensuremath{\theta})$ absolutely. Deduced $\ensuremath{\sigma}(E; {p}_{0})$, $\ensuremath{\sigma}(E; {p}_{1})$; $E1$, $E2$ strengths, isobaric analog states, isospin splitting. Natural target.