Charge exchange reactions of neutron-rich nuclei

Abstract

Charge exchange reactions of (p,n) and (d,2n) were measured for Li-11 and Li-9 nuclei employing the inverse kinematics and invariant mass methods at 63 A MeV. The experiments were performed at the RIKEN (Institute of Physical and Chemical Research) secondary beam line called RIPS (RIKEN Projectile fragment Separator). The isobaric analog state (IAS) of Li-11 nucleus in the relative energy spectrum of the Li-9 + p + n system produced by the H-1(Li-11,Be-11(sup star) to Li-9 + p + n)n reaction was observed. IAS has been identified by the comparison between the relative energy spectra for the H-1 and H-2 targets and the angular distribution of the Li-9 + p + n center-of-mass system. It was found that IAS mainly decayed, through an s-wave proton emission, to s-wave scattering states of the Li-9 + n system; which could be identified as an s-wave resonance. The excitation energy and width of IAS of Li-11 nucleus were deduced to be E(sub x) = 21.14 +/- 0.03 MeV and Gamma = 0.25 + 0.2/- 0.1 MeV, respectively, by an R-matrix analysis.

(p,n)と(d,2n)の荷電交換反応をLi-11とLi-9について63AMeVで、逆運動学と不変質量法を使って測定した。実験は理化学研究所のRIPS(理化学研究所破砕核分離装置)の2次ビームラインで行った。H-1(Li-11,Be-11(sup star) to Li-9 +p+n)n反応で生成したLi-9+p+n系の相対エネルギースペクトル中のLi-11核のアイソバリックアナログ状態(IAS)を観測した。IASはH-1とH-2標的に関する相対エネルギースペクトルと Li-9+p+n重心系での角度分布との間の比較で同定した。IASは主にs波陽子放出を通してLi-9+p+n系のs波散乱状態へと崩壊することがわかった。そしてこの状態はs波共鳴状態に同定できるかも知れない。Rマトリックス解析により、Li-11核のIASの励起エネルギー、E(sub x)=21.14+/-0.03MeV、そして励起幅、Γ=0.25+0.2/-0.1MeVを求めた。