# Beta+ decay for Z>N?

1. Jun 5, 2004

### arivero

I have just noticed that the nuclei with Z slightly greater than N have a peculiar pattern of b+ decay. Do someone know if this is justified from the Pauli Term of Weizsaecker formula?

[EDITED:] The phenomena is more apparent for Z=N+1, but just for these nuclei the Pauli Term $${(N-Z)^2\over A}$$ is zero, and only the EM term $$Z^2/A^{1/3}$$ contributes to decay energy.

Last edited: Jun 5, 2004
2. Jun 5, 2004

### swansont

What is peculiar about what you see?

3. Jun 5, 2004

### arivero

Well, for instance if you plot log(energy) vs log(halflife) you will notice that the data points adjust to two clearly distinct slopes.

Or, if you plot log(halflife), or halflife directly, versus atomic number A, you can notice two different groupings, depending of Z being greater or smaller than N. One of them does not present dependence on A, but the other clearly depends on A (or Z or N if you prefer).

4. Jun 5, 2004

### swansont

Can you post the graphs or a link to them?

5. Jun 6, 2004

### arivero

I'll try to upload some plot tomorrow Monday from the fac.

I think I could cope with the existence of a dependence Energy(AtomicNumber) for Z=N+1 even if the EM term does not fit well, because the dropplet model has another terms, such as $$Z^2 A^{1/3}$$, that could take responsability for this.

I am more intrigued about the difference in the dependence HalfLife(Energy) depending if the beta decay occurs for Z>=N or Z<N, ie, if the decaying proton goes to a lower neutron shell or to an upper one. It is not unexpected, but I would like to heard if people is usually able to get some properties of beta decay from this. Of course, the first step is to know if textbooks report this difference.

6. Jun 7, 2004

### arivero

Here are the plots

Hoping moderator approval, here are the plots I was speaking about. The second one, bpluslogT(A).jpg , shows decay time versus mass number for all the beta rays with intensity greater than 50%. The first one show log(E) versus Log(T), and the lower cluster corresponds very well to the hiperbole in the former plot.

I should say we are seeing the typical clusterings depending on if the transition is superallowed, allowed, etcetera... (a senior has been kind enough to partly confirm this). But still, it is impressive.

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