The decay of 20Na: Measurements of isospin mixing and the weak vector coupling constant as well as other new decay data

Abstract

Kinematic shifts of α particles from the β + delayed α decay of 20Na have been measured as a function of the energy of the coincident β + particles. Beta-neutrino-alpha triple-correlation coefficients were determined for six β + transitions from 20Na( J π , T = 2 +, 1) to excited 2 + states in 20Ne; ft values were also deduced. For the superallowed 2 + → 2 + transition to the T = 1 analogue state in 20Ne the results yielded a measurement of the vector weak coupling constant, G' V/( c) 3 = (1.103±0.028) × 10 −5GeV −2. For the other five (allowed Gamow-Teller) transitions, limits were established for the vector (Fermi) component and, from them, limits deduced on isospin mixing amplitudes for the daughter states in 20Ne. Weak, previously unknown, β-transitions were assigned to the decay of 20Na based on the observation of new α groups and one new γ-transition.