Radiative electron capture in the first-forbidden unique decay ofKr81

Abstract

The photon spectrum accompanying the orbital K-electron capture in the first-forbidden unique decay of 81 Kr was measured. The total radiation intensity for photon energies larger than 50 keV was found to be 1.42(22) × 10 −4per K capture. Both the shape of the spectrum and its intensity relative to the ordinary, nonradiative capture rate are compared to theoretical predictions. The best agreement is found for the recently developed model that employs the length gauge for the electromagnetic field.

Evidence for the virtualβ−γtransition inNi59decay

“…The nuclear contribution is strongly suppressed in this model but only when there are no close-lying excited states in the daughter or in the parent nucleus [28]. We note that for Λ = 1 we obtain the shape factor for the K-capture in 1u transition, which reproduced so well the experimental data [28,29]. In addition, the shape factor R 2nu , Eq.…”

“…The problem was caused by neglecting the radiation from the nucleus which is not justified in the Coulomb gauge. The length-gauge model, while reproducing exactly the results of Glauber and Martin for allowed decays, was found to describe very well both the shape and the intensity of experimental spectra of 41 Ca and 204 Tl [28] and later also the spectrum of 1u K-capture in 81 Kr [29]. It is because the nuclear radiation is strongly suppressed in this gauge and can be neglected.…”

Investigation of Electron Capture in 176Lu with a LYSO crystal scintillator

“…This photon contributes with his spin to the overall angular momentum conservation. The REC decay has been experimentally observed for the forbidden decay of: 41 Ca, 59 Ni, 81 Kr, 137 La and 204 Tl [17][18][19][20][21].…”