Evidence for core excitation in single-particle states of 19Na

Abstract

We present an experimental study of 19 Na states in the excitation energy range between 2 and 3 MeV. The presence of 19 Na single-particle levels at these energies was first predicted by a microscopic cluster model and then experimentally confirmed by measuring the elastic and inelastic scattering of a 66 MeV 18 Ne radioactive beam on a (CH 2 ) n target. The H( 18 Ne,p) 18 Ne(g.s.) and H( 18 Ne,p') 18 Ne*(2 + , 1.887 MeV) cross sections have been obtained in the laboratory angular range θ lab = 6.1 • −18.4 • and analyzed by using the R-matrix method. Two new states in 19 Na have been observed at centre of mass energies E c.m. = 2.78 ± 0.01 MeV and 3.09 ± 0.05 MeV. Both resonances exhibit large widths in the 18 Ne(2 + )+p channel, and low branching ratios into the elastic channel. The reduced proton widths confirm the single-particle nature of these states, with a 18 Ne(2 + )+p structure.

The8Li(p,α)5He reaction at low energies, andMendes1, Lépine‐Szily2, Descouvemont3 et al. 2012Phys. Rev. CSelf Cite

“…This technique has been used recently for other nuclei (see, for example, Ref. [30]) and would provide valuable information on the 9 Be structure near the proton threshold. A simultaneous study of the three proton-induced reactions is a challenge for future work.…”

Spectroscopic study of the exotic nucleusP25

“…where h (1) l is the Hankel function of the first kind [34] with orbital angular momentum l. The wave number κ n = √ 2μ n / is determined by the neutron separation energy n and the reduced mass μ of the last nucleon plus core. For isobar analogs of A N Z and A−1 N−1 Z the overlap I lj (r) has a different asymptotic behavior because at large r the Coulomb interactions between the last proton and the protons in A−1 Z (N − 1) break down the mirror symmetry and, in particular, when A Z N is unbound the asymptotics of I lj (r) will contain scattering waves [35][36][37].…”

“…Some states can be narrow because they are built on excited-core configurations. Examples of experimental evidence of such states can be found in 19 Na [1], 16 Ne [2], 15 F [2], 15 Ne [3], and 23 Al [4]. Theory also predicts excited-core-based narrow states in 17 Na [5][6][7] and 21 Al [8].…”

Core excitations and narrow states beyond the proton dripline: The exotic nucleus21Al

“…This can arise from a peculiar structure of such states wherein a few nucleons move around an excited core so that the main decay channel has much smaller energy and thus is held longer by the Coulomb barrier [2]. Experimentally, the existence of several such states was confirmed in 15 F, 16 Ne [2], and in 19 Na [3]. Theory also predicts narrow states in 17 Na (the mirror analog of 17 C) due to a large amplitude of the core excitations [4].…”