Summary
An experiment on the14N(α, γ)18F reaction leading to the parity- and isospin-forbidden 0+ level at 6.138 MeV is reported. A14N gas target was exposed to a pulsed singly charged α-particle beam from the CN accelerator of the Laboratori Nazionali di Legnaro, and γ-rays emitted in coincidence with the beam were measured with a 90 cm3 Ge(Li) detector. A similar run with the same target as well as an activation experiment were carried out on the nearby parity-allowed resonance at 6.241 MeV, in order to test the electronic gain and the efficiency in the parity-violating experiment. The energy spectrum from the Ge(Li) shows no peak due to the decay of the 6.138 MeV state and allows to set an upper limit of 2·10−3 eV for the parity-violating width of this resonance.
Riassunto
Si descrive un’esperienza sulla reazione14N(α, γ)18F che porti al livello 0+ a 6.138 MeV proibito dalla conservazione della parità e dell’isospin. Essa è basata sull'esposizione di un bersaglio gassoso di14N ad un fascio pulsato di particelle α con ionizzazione singola ottenuto con l’acceleratori CN dei Laboratori Nazionali di Legnaro e sulla misura dei raggi γ emessi in coincidenza col fascio misurati con un rivelatore Ge(Li) di 90 cm3. Per controllare il guadagno elettronico e l’efficienza della nostra esperienza sulla violazione della parità, si è compiuta un'esperienza simile sul livello vicino a 6.241 MeV, permesso dalla parità, con lo stesso bersaglio, nonché un’esperienza di attivazione. Lo spettro di energia ottenuto col Ge(Li) non mostra alcun picco dovuto al decadimento dello stato a 6.138 MeV e permette di porre un limite superiore di 2·10−3 eV sulla larghezza violante la parità di questa risonanza.
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Bellotti, E., Fiorini, E., Negri, P. et al. A search for hadronic nuclear-parity violation with change of isospin. Nuov Cim A 47, 106–114 (1978). https://doi.org/10.1007/BF02896230
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DOI: https://doi.org/10.1007/BF02896230