Il Nuovo Cimento (1955-1965)

, 39:442 | Cite as

Investigation of the96Nb disintegration scheme by means of a high-resolution lithium-ion drift germanium gamma-ray spectrometer

  • S. Monaro


The decay of the 24 h96Nb has been the subject of an extensive investigation in order to obtain more detailed information about the level structure of the even-even nucleus96Mo. For such a purpose, a high-resolution lithium-ion drift germanium γ-ray spectrometer has been used. The higher resolution of this γ-ray detector compared to the NaI scintilation spectrometers used in the previous investigations revealed the existence of several previously unreported γ-rays and allowed to measure their energies and intensities with high accuracy. For instance, the composite peak at about 800 keV in the spectrum of the96Nb decay was very well resolved in its 779, 811 and 851 keV components. Moreover, from the precision energy measurements of the transitions appearing in the decay of96Nb, it could be established that the 459.5, 569.3 and 811 keV γ-rays do not de-excite a single level of the even-even96Mo as previously reported, but the 459.5 keV transition de-excites a level at 2438.5 keV, whereas the 569.3 and 811 keV transitions de-excite a 2440.5 keV level. Furthermore, the existence of the second 2+ vibrational level at 1499 keV in96Mo, excited in the96Nb decay, has been shown and the value of the radio cascade/crossover has been measured and found equal to 2.27±0.55. From the measured value of the cascade/crossover ratio and from the knownɛB(E2)exp quantity, found by means of Coulomb excitation experiments, theB(E2, 2+′→0+) d andB(E2, 2+′→2+) d reduced electromagnetic transition rates for the second two plus state have been determined together with the ratioR=(B(E2, 2+′→2+) d )/(B(E2, 2+′→0+) d ). The results areB(E2, 2+′→0+) d ==(0.32±0.08)·10−50,B(E2, 2+′→2+) d =(3±0.95)·10−49 andR=0.97±0.30. These results support a collective model interpretation for the two 2+ levels in question.


Si è studiato con un contatore al litio-germanio il decadimento del96Nb 24 h. La migliore risoluzione di questo contatore in confronto a quelli al NaI usati nelle precedenti investìgazioni ha permesso di rivelare diversi raggi γ mai precedentemente trovati e di determinare la loro energia ed intensità con grande precisione. Per esempio si è potuto separare il picco composto a circa 300 keV nello spettro di decadimento del96Nb nei suoi tre componenti di 779, 811 e 851 keV. Si è potuto inoltre stabilire dalle accurate misure di energia dei raggi γ che le transizioni di 459.5, 569.3 e 811 keV non diseccitano un unico livello nel nucleo pari-pari96Mo, come si supponeva in precedenza, ma invece le due transizioni di 569.3 e 811 keV diseccitano un livello a 2 440.5 keV e la transizione di 459.5 keV un livello a 2 438.5 keV. Si è potuto anche stabilire l’esistenza di un secondo livello 2+ a 1 499 keV nel nucleo96Mo ed eccitato dal decadimento del96Nb. Si è misurato il rapporto « Cascade/Crossover » trovando un valore pari a 2.27±0.55. Da questo valore e dalla conoscenza della quantitàɛB(E2)exp misurata per mezzo della eccitazione coulombiana si sono potuti determinare i valori delle transizioni elettromagnetiche ridotteB(E2, 2+′→0+) d eB(E2, 2+′→2+) d per il secondo stato 2+ nel nucleo96Mo, assieme al rapportoR=B(E2, 2+′→2+) d /B(E2, 2+′→0+) d . I risultati sonoB(E2, 2+′→0+) d =(0.32±0.08)·10−50,B(E2, 2+′→2+) d =(3±0.95)·10−49 eR=0.97±0.30. Questi risultati rafforzano un’interpretazione di modello collettivo per i due livelli 2+ nel nucleo96Mo.


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Copyright information

© Società Italiana di Fisica 1965

Authors and Affiliations

  • S. Monaro
    • 1
  1. 1.Brookhaven National LaboratoryUpton

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