sig tot X(n, a) Y is less than the Sig P1+SigP2+Sigp3 where sigP1= sig{ X(n, 2n+p)Y----p-> Z}, sigP2= sig{ X(n, n+2p)U----n-> Z}, sigP1= sig{ X(n, He) Z}....
I think you meant sig tot X(n,a) Z? In that case the answer could be that Y or U can decay via other channels that do not lead to Z.
The general mechanism of X(n, a)Z is usually the formation of the compound nucleus, i. e. the formation of a high excited nucleus at intermediate state with relatively long time compared to the traversal time( an elapsed time for passing a nucleon through a nucleus:T=10^{-21}sec . According to Bohr hypothesis, the compound nucleus can form by different entrance channels and subsequently this nucleus decays through the different exit channels. One of assumptions for this model is that the formed compound nucleus forget the way of formation and the decay of the compound nucleus is independent of its formation. Therefore:
sig_{reaction}=sig_{formation}*sig_{decay}
In the X(n, a)Z reaction, the decay cross section, sig_{decay } includes all of decay channels, so that:
sig_{decay}=sum{i=1, n}sig_{production of specific radionuclide of Z}
As shown the above relations, the cross section of production of a specific radionuclide is less than the total formation cross section.
The total interaction cross-section is at least 10E4 - 10E6 times larger than any nuclear cross section.
- Badges
- Science topic
- Similar topics
- Clinical Pharmacology
- Dosing