S-factor

The astrophysical S-factor S(E) is a rescaled variant of the total cross section σ(E) that accounts for the Coulomb repulsion between charged reactants.

DefinitionEdit

The quantity is defined as^[1]

${\displaystyle S(E)\equiv {\frac {E}{\exp(-2\pi \eta )}}\sigma (E)}$

Here, η is the dimensionless Sommerfeld parameter,

${\displaystyle \eta \equiv {\frac {Z_{1}Z_{2}e^{2}}{4\pi \epsilon _{0}\hbar v}}}$

where

• Z₁ Z₂ e² is the product of the charges of the reactants and
• v is the magnitude of the relative incident velocity.

MotivationEdit

See also: Gamow factor

The Coulomb barrier causes the cross section to have a strong exponential dependence on the center-of-mass energy E. The S-factor remedies this by factoring out the Coulomb component of the cross section. 

This article uses material from the Wikipedia article  Metasyntactic variable, which is released under the  Creative Commons Attribution-ShareAlike 3.0 Unported License.