Étude expérimentale du premier état excité de ⁹Be

Abstract

The origin of the α-group from the ¹⁰B(t, α) reaction, sometimes but not always supposed to be associated with a level of ⁹Be between 1.65 and 1.80 MeV, has been carefully analysed as a monokinetic group by comparing the experimental variation of the peak versus the angle of emission for E_t = 1–3 MeV with other different possible theoretical processes: two-step reactions, three-step reactions and breakup with or without interaction in the final state. The excitation has been measured at 1750±25 keV, the corresponding width is 220±8 keV. The results of the same study with ⁹Be(α, α′)⁹Be are in agreement with these values. The angular distribution of the peak of ¹⁰B(t, α)⁹Be (1.75 MeV) has been analysed in DWBA at E_t = 2.5 MeV as a pick-up process and is, under this hypothesis, in agreement with $\text{J}{}_{\mathrm{\pi }}\text{=}\text{1}\text{2}{}^{\mathrm{+}}$. The parameters for the ingoing channel are deduced from a measurement of ¹⁰B(t, t)¹⁰B elastic scattering between 1 and 3 MeV.