The S Reaction Switch

The S switch is one of the parameters in the structure nhead in the directory of the `library' file, and its purpose is the tell the significance of some other parameters in nhead, namely, X₁, X₂, X₃, and X₄. For an explanation of nhead see Section 3.2.3.

0:

There is no X data.

1:

The parameter X₁ is the excitation level in Mev.

2:

These are pre-equilibrium and unresolved direct-interaction processes, and there is no X data. Note for example, that the ENDL library has two separate ²³⁵U(n,$\gamma$) reactions ( $\tt C$ = 46), a cluster reaction with $\tt S$ = 0 and a direct-interaction process with $\tt S$ = 2.

3:

We have gamma-ray production, and X₁ is the energy of the emitted photon in Mev.

5:

This is an activation process, X₁ = 1000*Z + A to identify the atomic number and mass number of the residual, X₂ is the excitation level of the residual in Mev, and X₃ is its halflife in seconds.

7:

We have delayed fission groups, and X₁ is the halflife of this group. But if X₁ = 0, then the data is a sum over all delayed groups.

8:

This is a time-sequential cluster model, and X₁ gives the excitation level in Mev.

91:

In this case X₁ designates the subshell.