Physics Division Seminars bring us speakers on a variety of physics related subjects. Usually these are held in the Building 6008 large Conference Room, at 3:00 pm on the chosen day, but times and locations may vary. For more information, contact our seminar chairman,
Tel (Office): (865) 574-6124 (FAX): (865) 574-1268
In the nuclear electron capture (EC) decay sometimes, with a probability of about 10-4, a photon is emitted together with an electron neutrino. Such a process is called radiative electron capture (REC). Our Warsaw group has been investigating this phenomenon over many years, focusing, in particular, on forbidden transitions. These studies revealed a strong disagreement of measured spectra with theoretical models. This was especially puzzling in case of first-forbidden unique (1u) decays, where the observed gamma spectrum should be determined solely by quantum electrodynamics, as the nuclear matrix elements cancel out. A few years ago, a new theoretical description succeeded to finally solve the REC puzzle for the decays of 1u type. Recently, we have extended this model also to second forbidden non-unique (2nu) decays and we applied it to the case of 59Ni, measured already long time ago. The result was surprising - it yielded the first evidence for a virtual beta-gamma transition. A possibility for such a virtual decay path was predicted already in the sixties, but all attempts to observe it were unsuccessful. The present identification of this phenomenon was possible due to the new, correct theoretical description of the radiative EC decays. In my talk, I will present a long path leading us to the understanding of this basic nuclear process.
Contact: Alfredo Galindo-Uribarri (865) 574-6124