Coulomb suppression of the stellar enhancement factor

TL;DR

This paper demonstrates that stellar effects can be minimized in charged particle reactions with negative Q values, using the 85Rb(p,n)85Sr reaction as a case study, and confirms a modification of the optical proton potential.

Contribution

It shows that the stellar enhancement factor can be suppressed in charged particle channels even with negative Q values, challenging common assumptions.

Findings

Measured the 85Rb(p,n)85Sr cross section between 2.16 and 3.96 MeV.

Inferred astrophysical reaction rates for (p,n) and (n,p) channels.

Confirmed a modification of the global optical proton potential.

Abstract

It is commonly assumed that reaction measurements for astrophysics should be preferably performed in the direction of positive Q value to minimize the impact of the stellar enhancement factor, i.e. the difference between the laboratory rate and the actual stellar rate. We show that the stellar effects can be minimized in the charged particle channel, even when the reaction Q value is negative. As a demonstration, the cross section of the astrophysically relevant 85Rb(p,n)85Sr reaction has been measured by activation between 2.16 < Ec.m. < 3.96 MeV and the astrophysical reaction rate for (p,n) as well as (n,p) is directly inferred from the data. The presented arguments are also relevant for other alpha and proton-induced reactions in the p and rp processes. Additionally, our results confirm a previously derived modification of a global optical proton potential.