Beta Disintegration: Nucleus Absorbing Electrons & Positrons

[ziad1985]

I was studying Beta decay in my nuclear courses few minutes ago, and something came to my attention.
A nucleus can absorb an electron and undergo a beta decay like this:
p + e- ----> n + neutrino
Is the following one possible?
n + e+ ----> p + anti-neutrino?
where a nucleus absorb an positron and undergo a beta decay?

 

[cristo]

I'm not sure whether you're talking about beta decay here, since the beta (minus) decay I recall learning was n--->p+e-+ anti-neutrino. This is called beta-minus, since the beta particle emitted (here the electron) is negative. Of course, to this there is a corresponding beta plus decay: p--->n+ e+ +neutrino, however this requires energy, and so cannot occur in isolation, unlike the beta- decay.

What you seem to be describing, p+e- ---> n+neutrino is what I would call "electron capture," where the nucleus captures an orbiting electron. Thus, I don't think that your second scenario would be allowed, since there are no orbiting positrons.

 

[ziad1985]

Sorry for that, it's a problem when you know something in a 2nd language, and try to explain it in a third one.
(From French to English, and neither are my maternal language)
What I want to know is :
since p + e- ----> n + neutrino is allowed
is n + e+ ----> p + anti-neutrino allowed?
I know that there is no positrons orbiting, but is that the only reason, or is there something else?
if there is no way for a nucleus to absorb a positron , how about (e+,n) scattering? will it be possible then?

 

[Parlyne]

There's really nothing that could forbid a positron capture. It won't happen very often, simply because positrons are rare to begin with and would be repelled by the protons in a nucleus, while lone neutrons decay. However, it should certainly be possible.