Monday 27 August 2018

nuclear physics - What is the "penetrability factor"?


I have read/heard this term a few times in nuclear physics papers. I'm guessing it has something to do with the Coloumb barrier of a nucleus. Could you maybe explain what this "penetrability factor" is?


[See page 63 of this paper]



Answer



The penetrability factor is a carefully defined factor that separates the coulomb-force and the interesting nuclear-forces in the relationship between the partial decay width and the reduced width (for R-Matrix analysis) of a particular resonance.


$$\Gamma = 2\gamma^2P(l,\rho,\eta)$$


Here $\Gamma$ is the partial decay width, $\gamma$ is the reduced width, $l$ is the orbital angular momentum of the state, $\rho$ is defined as $k$ (wavenumber) multiplied by $r$ the target particle radius, $\eta$ is the sommerfeld [nuclear] parameter, and $P(l,\eta,\rho)$ is the penetrability factor. The penetrability factor is defined as,



$$P(l,\rho,\eta)=\frac{\rho}{\left(F_l (\eta,\rho)\right)^2+\left(G_l (\eta,\rho)\right)^2}$$


where $F$ and $G$ are the regular and irregular coulomb wave functions, respectively.


Source: http://www.scholarpedia.org/article/The_R-matrix_theory_in_nuclear_and_atomic_physics (equation 10 and 13)


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