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Hirabayashi, Y.; Ohkubo, S.

doi:10.1103/physrevc.88.014314

Cited by 21 publications

(25 citation statements)

References 30 publications

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“…The phenomenon was first discussed in connection with 16 O(α,α) 16 O and 40 Ca(α,α) 40 Ca elastic scattering. For these reactions it was noticed later that the so-called anomalous cross sections are related to weak absorption of the doubly-magic target nuclei, and it is possible to describe the angular distributions within the OM [64][65][66][67][68][69]. Contrary to these findings, it turned out that the reproduction of the backward angular range in, e.g., 6 Li(α,α) 6 Li or 20 Ne(α,α) 20 Ne remains extremely difficult, and various explanations for the backward rise have been suggested: inelastic coupling to low-lying excited states, compound-elastic contributions, elastic α transfer, and angular-momentum-dependent absorption (e.g., [70][71][72][73]).…”

Section: Alas For 64 Zn?mentioning

confidence: 99%

“…Inelastic scattering leading to the first four exited states of 64 Zn was also measured in an angular range limited to a more backward region. Using the activation technique, the cross sections of the 64 Zn(α,γ ) 68 Ge, 64 Zn(α,n) 67 Ge, and 64 Zn(α,p) 67 Ga reactions were also measured at the same energies. Since the experimental techniques of both the scattering and activation experiments were already described in detail elsewhere [9,37], here only the most important features of the measurements and the results are presented.…”

Section: Experimental Setup and Proceduresmentioning

confidence: 99%

“…The cyclotron accelerator provided the α beam which bombarded a thin natural isotopic composition Zn target on Al foil backing. The number of the 68 Ge, 67 Ge, and 67 Ga isotopes produced by the 64 Zn(α,γ ) 68 Ge, 64 Zn(α,n) 67 Ge, and 64 Zn(α,p) 67 Ga reactions, respectively, was determined offline by measuring the γ radiation following the decay of the reaction products with a shielded 100% relative efficiency HPGe detector. Table I summarizes the results of the activation crosssection measurements.…”

Section: B Activation Experimentsmentioning

confidence: 99%

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α scattering and α -induced reaction cross sections of Zn64 at low energies

Ornelas¹,

Mohr²,

Gyürky³

et al. 2016

Phys. Rev. C

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Background: α-nucleus potentials play an essential role for the calculation of α-induced reaction cross sections at low energies in the statistical model. Uncertainties of these calculations are related to ambiguities in the adjustment of the potential parameters to experimental elastic scattering angular distributions and to the energy dependence of the effective α-nucleus potentials. Purpose: The present work studies the total reaction cross section σ reac of α-induced reactions at low energies which can be determined from the elastic scattering angular distribution or from the sum over the cross sections of all open nonelastic channels. Method: Elastic and inelastic64 Zn(α,α) 64 Zn angular distributions were measured at two energies around the Coulomb barrier, at 12.1 and 16.1 MeV. Reaction cross sections of the (α,γ ), (α,n), and (α,p) reactions were measured at the same energies using the activation technique. The contributions of missing nonelastic channels were estimated from statistical model calculations. Results: The total reaction cross sections from elastic scattering and from the sum of the cross sections over all open nonelastic channels agree well within the uncertainties. This finding confirms the consistency of the experimental data. At the higher energy of 16.1 MeV, the predicted significant contribution of compound-inelastic scattering to the total reaction cross section is confirmed experimentally. As a by-product it is found that most recent global α-nucleus potentials are able to describe the reaction cross sections for 64 Zn around the Coulomb barrier. Conclusions: Total reaction cross sections of α-induced reactions can be well determined from elastic scattering angular distributions. The present study proves experimentally that the total cross section from elastic scattering is identical to the sum of nonelastic reaction cross sections. Thus, the statistical model can reliably be used to distribute the total reaction cross section among the different open channels.

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Section: Alas For 64 Zn?mentioning

confidence: 99%

Section: Experimental Setup and Proceduresmentioning

confidence: 99%

Section: B Activation Experimentsmentioning

confidence: 99%

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α scattering and α -induced reaction cross sections of Zn64 at low energies

Ornelas¹,

Mohr²,

Gyürky³

et al. 2016

Phys. Rev. C

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“…Inelastic rainbow scattering has also been especially powerful in understanding the highly excited cluster structure near and above the threshold energy, such as the α particle condensation of the Hoyle state in 12 C and the Hoyle-analog state in 16 O [21][22][23][24][25]. A recent systematic study of the evolution of the Airy structure in inelastic scattering for the typical α+ 16 O system [26] showed that the cluster structure with core excitation in 20 Ne near the threshold energy region and the inelastic nuclear rainbow scattering can be understood in a unified way by using reliable interaction potentials for the inelastic channels. This urges us to study inelastic rainbow scattering with heavy ions in order to determine the interaction potentials in inelastic channels, which will make it possible to understand the molecular structure with core excitation, for which phenomenological shallow potentials have been used widely instead of a deep potential [27].…”

Section: O+mentioning

confidence: 99%

Refractive effects and Airy structure in inelasticO16+C12rainbow scattering

et al. 2014

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Inelastic16 O + 12 C rainbow scattering to the 2 + (4.44 MeV) state of 12 C was measured at the incident energies, EL = 170, 181, 200, 260 and 281 MeV. A systematic analysis of the experimental angular distributions was performed using the coupled channels method with an extended double folding potential derived from realistic wave functions for 12 C and 16 O calculated with a microscopic α cluster model and a finite-range density-dependent nucleon-nucleon force. The coupled channels analysis of the measured inelastic scattering data shows consistently some Airy-like structure in the inelastic scattering cross sections for the first 2 + state of 12 C, which is somewhat obscured and still not clearly visible in the measured data. The Airy minimum was identified from the analysis and the systematic energy evolution of the Airy structure was studied. The Airy minimum in inelastic scattering is found to be shifted backward compared with that in elastic scattering.

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“…[21], which reproduces almost all the energy levels well up to E x ≈ 13 MeV and the electric transition probabilities in 16 O. The wave functions have been successfully used for the systematic analysis of elastic and inelastic α + 16 O scattering over a wide range of incident energies and the α cluster structure study of 20 Ne [22]. ρ 12 C, which is calculated using the microscopic three-α-cluster model in the resonating group method [23].…”

mentioning

confidence: 99%

Evidence for a secondary bow in Newton's zero-order nuclear rainbow

Ohkubo

Hirabayashi

2014

Phys. Rev. C

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Rainbows are generally considered to be caused by static refraction and reflection. A primary and a secondary rainbow appear due to refraction and internal reflection in a raindrop as explained by Newton. The quantum nuclear rainbow, which is generated by refraction in the nucleus droplet, only has a "primary" rainbow. Here we show for the first time evidence for the existence of a secondary nuclear rainbow generated dynamically by coupling to an excited state without internal reflection. This has been demonstrated for experimental 16 Newton, who explained the mechanism of the rainbow by refraction and reflection [1][2][3], believed in the existence of the zero-order rainbow without internal reflection in a droplet. Newton's zero-order rainbow [4] was realized in quantum systems when Goldberg et al.[5] observed a nuclear rainbow in high-energy α-particle scattering. The quantum nuclear rainbow is generated by the nuclear potential, which acts as a Luneburg lens [6], where refraction is the only active mechanism and a "primary" rainbow can only exist because there are no higher-order terms like in Nussenzveig's expansion for the meteorological rainbow [7]. We report here evidence for the unexpected existence of a secondary bow in the nuclear rainbow.The nuclear rainbow is very important in determining the interaction potential family up to the internal region without discrete ambiguity [5] and has been studied extensively [8,9]. The nuclear rainbow is also powerful for studies of nuclear cluster structure in the bound and unbound energy regions. In fact, the global nuclear potential, which describes nuclear rainbow scattering for typical α + 16 O, α + 40 Ca, and 16 O + 16 O systems, can reproduce scattering over a wide range of incident energies and cluster structures of 20 Ne, 44 Ti, and 32 S in the bound and unbound energy regions, respectively, in a unified way [10][11][12]. In contrast to the 16 O + 16 O system, the Airy structure of the nuclear rainbow for the asymmetric 16 O + 12 C system, for which refraction is very strong, is clearly observed in experimental angular distributions without being obscured by symmetrization. For this system, a global potential that reproduces the energy evolution of the Airy minimum in the angular distributions over a wide range of incident energies at E L = 62 ∼1503 MeV [13][14][15][16][17] • ). It has been impossible to model a first-order Airy minimum A1 at this large angle with the established global potential [19]. Thus, the reason why the global potential fails to reproduce the Airy minimum of the nuclear rainbow at E L = 281 MeV has been a mystery and raised a serious question of the common belief that nuclear rainbow scattering can determine the potential uniquely.The purpose of this paper is to present for the first time evidence for the existence of a secondary nuclear rainbow in the 16 O + 12 C scattering generated dynamically by a quantum effect without internal reflections of classical concept, which is completely different from the Newton's meteorological se...

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Unification of Airy structure in inelasticα+16O scattering andα-cluster structure with core excitation in20

Cited by 21 publications

References 30 publications

α scattering and α -induced reaction cross sections of Zn64 at low energies

α scattering and α -induced reaction cross sections of Zn64 at low energies

Refractive effects and Airy structure in inelasticO16+C12rainbow scattering

Evidence for a secondary bow in Newton's zero-order nuclear rainbow

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