Astrophysically important26Sistates studied with the28Si

Abstract

The production of the 26 Al radioisotope in astrophysical environments is not understood, in part, because of large uncertainties in key nuclear reaction rates. The 25 Al(p,␥) 26 Si reaction is one of the most important, but its rate is very uncertain as a result of the lack of information on the 26 Si level structure above the proton threshold. To reduce these uncertainties, we have measured differential cross sections for the 28 Si(p,t) 26 Si reaction and determined excitation energies for states in 26 Si. A total of 21 states in 26 Si were observed, including ten above the proton threshold. One new state at 7019 keV was observed, the excitation energies of several states were corrected, and the uncertainties in the excitation energies of other states were significantly reduced. Spins and parities of several states above the proton threshold were determined for the first time through a distorted-wave Born approximation analysis of the angular distributions. These results substantially clarify the level structure of 26 Si.

High-precision mass measurements of 25Al and 30P at JYFLTRAP

“…Gamma-decay studies of 26 Si performed at Gammasphere [54,60] have shown that there is a 4 + state at 5517.0 keV, a 1 + level at 5675.9 keV and a 0 + state at 5890.1 keV. A 3 + state at 5928.7 keV has been confirmed via beta-decay studies of 26 P [51,58] and it is also supported by [50,53,56]. The spin for the next excited state at 5946 keV is unclear.…”

“…The knowledge of these states has improved considerably thanks to several measurements on the excited levels of 26 Si [49][50][51][52][53][54][55][56][57][58][59][60][61]. Gamma-decay studies of 26 Si performed at Gammasphere [54,60] have shown that there is a 4 + state at 5517.0 keV, a 1 + level at 5675.9 keV and a 0 + state at 5890.1 keV.…”

Nuclear structure of30S and its implications for nucleosynthesis in classical novae

“…A decrease in the abundance of 30 P consequently reduces that of 30 Si produced from 30 P(β + ) 30 Si. The rate of the 30 P(p, γ) 31 S reaction has been evaluated in Refs. [8,67,68] and more recently in Ref.…”

“…In § I, it was emphasized that 29,30 P(p, γ) 30,31 S are the two reactions that are thought to affect the silicon isotopic ratios in nova ejecta.…”

26Si excited states via one-neutron removal from a27Si radioactive ion beam

“…Since a direct measurement of the 25 Al(p,γ) 26 Si reaction is presently untenable due to insufficiently intense beams of 25 Al, transfer reactions and in-beam gamma-ray spectroscopic studies have been used extensively to determine indirectly the important level properties of 26 Si, such as resonance energies and spin-parity assignments [1,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. The rate has been re-evaluated recently [23,[26][27][28], and Ref.…”