The proton capture reactions on21Na and22Na under hydrogen burning conditions

Abstract

We have updated and recalculated the ZlNa(p,T)ZZMg and 22Na(p, 7)Z3Mg reaction rates for temperatures 107-109K relevant for explosive hydrogen burning in stellar environment. We find the 21Na(p, 7)ZZMg rate lower than recently suggested. Considering various uncertainties in spin and parity assignments of the low energy ZeNa+p resonances we present upper and lower limits for the 22Na(p, 7)23Mg reaction rate which, however, allows for a meaningful discussion of the consequences of the new rates on the Ne-Na cycle under various stellar conditions.

Nuclear Uncertainties in the NeNa‐MgAl Cycles and Production of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcy

“…Estimates of the 21Na(p, c)22Mg reaction rate (CF88) have been provided by and Wiescher & Langanke (1986), considering the Ðrst three levels (Endt 1990) above the proton threshold. With the exception of the Ðrst level, the proton widths are much larger than the c-widths, so that Only the Ðrst two levels and 5.837 MeV) uc B u!…”

Synthesis of the elements in stars: forty years of progress

“…Measurements by Wiescher et al (1989) had indicated that the cross section for this reaction was a factor of 2 smaller than reported by Imhof et al (1959), thereby reducing the rate of heavy element synthesis in any primordial r process. However, a number of more recent measurements (Blackmon et al, 1996, and references therein) are in good agreement with the Imhof (1959) results supporting the reaction rate used in the calculation of heavy element production by Malaney and Fowler (1987).…”

“…A number of authors (Wiescher and Langanke, 1986;Wiescher et al, 1988, van Wormer et al, 1994Herndl et al, 1995;Iliadis et al, 1996b) have examined the reactions in this mass region and have used similar procedures for obtaining resonance parameters. All make use of the known properties of states in stable isobars.…”

“…Proton widths were calculated from both experimental and theoretical single-particle spectroscopic factors. In the case of the 21 Na(p,␥) reaction, the magnitude of the energy shift between analogous states in 22 Mg and 22 Na was used to calculate single-particle reduced widths (Wiescher and Langanke, 1986). This procedure assumes that the states in question are primarily pure single-particle states and this must be justified on a state by state basis.…”

A study of the proton resonant property in 22Mg by elastic scattering of 21Na + p and its astrophysical implication in the 18Ne(α, p)21Na reaction rate

“…The structure of 22 Mg has received great interest in recent years because of its important role in determining the astrophysical reaction rates of 21 Na(p, γ) 22 Mg and 18 Ne(α, p) 21 Na reactions in explosive stellar scenarios [1,2].…”