Deformation effects in the compound nucleus decay using the spin-alignment method

Nicolis, N. G.; Sarantites, D. G.; Adler, Laszlo; Dilmanian, F.A.; Honkanen, K.; Majka, Z.; Sobotka, L. G.; Li, Z.; Semkow, T.M.; Beene, J. R.; Halbert, M. L.; Hensley, D. C.; Natowitz, J. B.; Schmitt, R.; Fabris, D.; Nebbia, G.; Mouchaty, G.

doi:10.1103/physrevc.41.2118

Cited by 24 publications

(11 citation statements)

References 36 publications

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“…We will also integrate previous work done at lower energy (143 MeV) on the same reaction [1][2][3][4][5][6]7], where the evidence of a purely statistical gammadecay of nuclei formed in deep inelastic reactions and a strong non-statistical ):-emission in the quasi-elastic region was found.…”

Section: Introductionmentioning

confidence: 84%

“…Regarding the alpha-particles emitted with an energy lower than the Coulomb barrier (region I), in some papers [2,17] they were explained as originating from deformed fused nuclei. This effect cannot be neglected in our reaction (compound nucleus 92Mo) for which GDR deexcitation studies showed the presence of deformation [18].…”

Section: Alpha Particlementioning

confidence: 99%

“…In the present paper we investigate on the gamma-ray multiplicity behavior in the reaction2SSi+64Ni at 163.8 MeV with the aim to solve the contradiction between [1][2][3] and [4]. We will also integrate previous work done at lower energy (143 MeV) on the same reaction [1][2][3][4][5][6]7], where the evidence of a purely statistical gammadecay of nuclei formed in deep inelastic reactions and a strong non-statistical ):-emission in the quasi-elastic region was found.…”

Section: Introductionmentioning

confidence: 99%

“…Recent examples can be found in [2][3][4][5] for fusion and dissipative reactions. The major uncertainty in these analyses arises from the connection between the mean measured ):-ray multiplicity (Mr) and the mean spin of the excited nuclei.…”

Section: Introductionmentioning

confidence: 99%

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Gamma-ray multiplicity measurements in the28Si+64Ni reaction at 163.8 MeV

Pietro

Cardella

Musumarra

et al. 1994

Z. Physik A - Hadrons and Nuclei

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Abstract. The 28Si + 64Ni reaction at 163.8 MeV incident energy is studied by measuring in coincidence 7-rays and charged particles identified from Z=2 to Z=16. The transition from quasi-elastic to more damped reactions is observed when the difference between the detected charge and the projectile one is increased. The strong influence of the particle decay on the measured ):-ray multiplicity is evidenced with the help of the statistical model computer code CASCADE. Dissipative events are well described in the rolling limit with excitation energy equally shared between the fragments. The overall agreement is lost for the fragments with the projectile charge which show a small value of the 7-multiplicity even for dissipative events. This is probably connected with the previously observed non statistical behavior of gamma rays emitted in coincidence with projectile-like fragments. In the alpha-spectrum measured in coincidence with gamma-rays, the deexcitation of fused systems is clearly separated from in flight emission of deep inelastic fragments. The low measured gamma-ray multiplicity for fusion events is qualitatively explained taking into account the effect of alpha-emission in the statistical decay.

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Section: Introductionmentioning

confidence: 84%

Section: Alpha Particlementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Gamma-ray multiplicity measurements in the28Si+64Ni reaction at 163.8 MeV

Pietro

Cardella

Musumarra

et al. 1994

Z. Physik A - Hadrons and Nuclei

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“…Grover and Gilat first discussed this process in work published 25 years ago [5]. These early calculations, as well as more recent ones [7], predict that these "stretched" and "last chance" o. particles would be emitted &om states with lifetimes similar to the K-vacancy lifetime and therefore present an ideal application of the atoxnic clock xnethod. The predicted a-particle energies are low for these "last chance" particle emissions which, despite the angular moxnentum removed by the decay, tend to populate moderate to high spin states of the residue.…”

mentioning

confidence: 99%

Estimation of the time scale of last chance alpha emission using an ‘‘atomic clock’’

et al. 1994

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The probability of Slling a K-vacancy, created on the incoming part of the coQision, before nparticle emission is used to time the decay of Yb compound nuclei. These nuclei were produced in the fusion reaction 250 MeV Ni + Mo. In general the nuclear decays are too fast to be timed by this clock, however, n-particle emitting compound nucleus states have lifetimes sufBciently long for this technique to work when both the a-particle has low energy and the compound nucleus spin is large. This supports the existence of last, or near last, chance o;-particle emission in the deexcitation of high spin compound nuclei.PACS number(s): 24.60. Dr, 25.70.Gh Thirty years ago Gugelot [1] pointed out that one can calibrate the decay width (I', ) of a compound nucleus in terms of the K x-ray width (I' ) for atomic vacancies. All one has to do is prepare an atoxn with an excited nucleus and a K vacancy and then measure the branching ratio I' /I', . In practice, there are several problems in applying this idea. The K-vacancy production probabilities P~are low (of the order of 1%) for typical low energy fusion reactions and, in contrast to atomic collisions below the Coulomb barrier, the x rays of interest must be detected in a large background resulting &om internal conversion x rays and p rays emitted by excited nuclear reaction products. Another important issue is photon production from the filling of vacancies in a charged particle exit channel during the time after exnission but before the emitted particle is well outside the K-shell Bohr radius (molecular orbital emission). Due to these problems, this old idea has met with success only recently [2][3][4].This technique is best suited to the study of the lifetimes of last or near last chance decays of compound systems in the bottom portion (high charge) of the periodic table. Only under these conditions does the K-vacancy lifetime approach the compound nuclear lifetime. Two interesting topics for which this technique is quite promising are: (1) the study of slow fission components and (2) slow "yrast" a-particle emission. The former involves actinide nuclei for which the K-vacancy lifetime is less than 10~s, and the latter, heavy rare earth nuclei with Kvacancy lifetixnes between 10 and 10 s. The recent paper by Molitoris et al. [4] addresses the first of these topics and this work deals with the second.Statistical model codes predict that the emission of a particles competes with p-ray emission at very low excitation energies when the nuclei are trapped near the yrast line at high to moderate spins [5,6]. Grover and Gilat first discussed this process in work published 25 years ago [5]. These early calculations, as well as more recent ones [7], predict that these "stretched" and "last chance" o. particles would be emitted &om states with lifetimes similar to the K-vacancy lifetime and therefore present an ideal application of the atoxnic clock xnethod. The predicted a-particle energies are low for these "last chance" particle emissions which, despite the angular moxnentum re...

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