Why does electron capture occur and under what conditions?

[Reshma]

Electron capture is a form of beta-decay. Here, an orbital electron(usually in K-shell) can combine with proton to form a neutron and a neutrino. $$p + \beta^{-}\rightarrow n + \nu$$

Can someone explain me why this phenomenon occurs and under what conditions?

 

[nishant]

from the equation itself it shows that it occurs so that the n/p ratio increases

 

[SpaceTiger]

This reaction occurs in the cores of massive stars when they're undergoing the transition to a neutron star (as might be obvious from the name), so high density is certainly one condition in which it might occur. This process also occurs in the early universe during nuceosynthesis, when there is an equilibrium between proton and neutron-creating processes. This, of course, is at very high temperature.

 

[mathman]

The reaction occurs in radioactive isotopes where the proton to neutron ratio is too high. Positron emission leads to the same result, so these tend to be competitive.

 

[Meir Achuz]

The process is usually called "K capture" from an archaic designation of electron shells as K,L,M,... The K shell is the innermost one, and its electrons can be captured as the other posts said.