Astrophysics and Charge-Exchange

Electron-capture reactions are important in a variety of astrophysical phenomena. For example, electron-captures play a prominent role in the late evolution of stars, just before they become supernovae. To help understand such explosions, such as Type 1a (thermonuclear) and Type II (core collapse) supernova, electron-capture rates for many nuclei most be known with reasonable accuracy. These rates are calculated from nuclear structure data. Since there are many relevant nuclei and transitions may occur from excited states, theoretical models are necessary. Data from experiments validates theoretical calculations and improves the underlying models.

Charge-exchange and electron-capture reactions connect the same initial and final states of the mother and daughter nuclei. For example, consider the (t,³He) charge-exchange reaction on ⁵⁸Ni, which produces ⁵⁸Co. If the same ⁵⁸Ni nucleus were to capture an electron, one of its protons would be converted to a neutron (while producing a neutrino), leaving a ⁵⁸Co nucleus; the same nuclear product. Even though the forces that drive these charge-exchange and electron-capture reactions are different (the strong and the weak force, respectively), the nuclear structure information (the Gamow-Teller strength) needed to calculate electron capture rates can be extracted from cross section measurements in charge-exchange experiments.

the remnent from a Type 1a supernova explosion (white dot in the square)