Large angle scattering of 100 MeV α-particles from 40, 44, 48Ca

Eickhoff, H.; Frekers, D.; Löhner, H.; Poppensieker, K.; Santo, R.; Gaul, G.; Mayer‐Böricke, C.; Turek, P.

doi:10.1016/0375-9474(75)90503-5

Cited by 49 publications

(18 citation statements)

References 20 publications

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“…In agreement with expectations based on previous data there is a back-angle enhancement of 4~ for energies below 50MeV accompanied by a pronounced structure of the backward angular distribution. At E~ = 61.0 MeV, however, the oscillatory character of the angular distributions is strongly reduced at intermediate angles and the curves are more similar to the data at higher energies [15,16], which are characterized by a smoothly decreasing slope of the cross section following the diffraction region.…”

Section: Experimental Procedures and Resultsmentioning

confidence: 51%

Investigation of large angle structure in ?-scattering from calcium isotopes betweenE ?=36?61 MeV

et al. 1978

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Elastic c~-scattering angular distributions have been measured at E~=36.2MeV, 39.6MeV, 42.6MeV, 49.5MeV, 61.0MeV for 4~ and at E~=36.2MeV, 42.6MeV, 49.5 MeV and 61.0 MeV for 44Ca, respectively. At backward angles the data display an oscillatory structure for E~<50MeV and more smoothly decreasing slopes at E~ =61.0MeV resembling the data obtained at higher energies. The 4~ data below E~ =50MeV show the well known backward enhancement, which at 42.6MeV and 49.5 MeV can be fitted by a p2 and a P~ respectively. Together with previous data, p2_ structures have now been observed for all L-values between L= 8 and L= 16. The slope of the curve L(L + 1) versus excitation energy is slightly smaller for L > 12 than for L < 12. Optical model analyses (within a Woods-Saxon-folding model) lead to large differences between the 44Ca and 4~ parameters. Furthermore, in our parametrization, the 4~ real potential depth shows dramatic changes with energy. This feature seems outside the domain of the optical model and requires consideration of additional effects (e.g. antisymmetrization) not included in the standard optical model. Present microscopic ,calculations on the basis of the Resonating Group Method are discussed in connection with the characteristic features of e-scattering from 4~

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Section: Experimental Procedures and Resultsmentioning

confidence: 51%

Investigation of large angle structure in ?-scattering from calcium isotopes betweenE ?=36?61 MeV

et al. 1978

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“…The α clustering is essential in the 0p-shell and sd shell region and the nuclear structure has been comprehensively understood from the α cluster viewpoint [1]. In the f p shell region, identification of the higher nodal band states with the α+ 40 Ca cluster structure in the fusion excitation functions [2] lead to the prediction of a K = 0 − band, which is a parity-doublet partner of the ground band, in the typical nucleus 44 Ti [3][4][5]. The observation of the K = 0 − band in experiment [6,7] showed that the α cluster picture is also essential in 44 Ti.…”

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confidence: 99%

Existence of higher nodal band states withα+Ca48cluster structure inTi52

Ohkubo

2020

Phys. Rev. C

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It is shown that recently observed α cluster states a few MeV above the α threshold energy in 52 Ti correspond to the higher nodal band states with the α+ 48 Ca cluster structure, i.e. a vibrational mode in which the intercluster relative motion is excited. The existence of the higher nodal states in the 48 Ca core region in addition to the well-known higher nodal states in 20 Ne and 44 Ti reinforces the importance of the concept of vibrational motion due to clustering even in medium-weight nuclei with a jj-shell closed core. The higher nodal band and the shell-like ground band in 52 Ti are described in a unified way by a Luneburg lens-like deep local potential due to the Pauli principle, which explains the emergence of backward angle anomaly (anomalous large angle scattering (ALAS)) at low energies, prerainbows at intermediate energies and nuclear rainbows at high energies in α+ 48 Ca scattering. The existence of a K = 0 − α cluster band analog to 44 Ti midway between the ground band and the higher nodal band is inevitably predicted.The α clustering is essential in the 0p-shell and sd shell region and the nuclear structure has been comprehensively understood from the α cluster viewpoint [1]. In the f p shell region, identification of the higher nodal band states with the α+ 40 Ca cluster structure in the fusion excitation functions [2] lead to the prediction of a K = 0 − band, which is a parity-doublet partner of the ground band, in the typical nucleus 44 Ti [3-5]. The observation of the K = 0 − band in experiment [6,7] showed that the α cluster picture is also essential in 44 Ti. Systematic theoretical and experimental studies in the 44 Ti region [8][9][10][11][12][13] confirmed the existence of the α cluster in the beginning of the f p-shell above the double magic nucleus 40 Ca.α clustering aspects in nuclei beyond 44 Ti have been explored in the medium weight mass region around A=50 such as 48 Cr [14,15] and 46,50 Cr [16,17] as well as in the heavy mass region such as 94 Mo and 212 Po [18][19][20][21]. 52 Ti, which is a typical nucleus with two protons and two neutrons outside the doubly closed core 48 Ca analog to 20 Ne and 44 Ti, has been mostly studied in the shell model [22][23][24][25][26][27]. The ground band 0 + , 2 + and 4 + states are selectively enhanced in the α-transfer reactions such as 48 Ca( 16 O, 12 C) 52 Ti [28] and 48 Ca( 12 C, 8 Be) 52 Ti [29]. However a microscopic α+ 48 Ca cluster model calculation with Brink-Boeker force B1 using the generator coordinate method (GCM) [30] did not give the ground band as well as in the α+ 40 Ca cluster model calculation for 44 Ti. On the other hand, Ohkubo et al. [31] and Ohkubo and Hiraoka[32] reproduced the ground band of 52 Ti in the α cluster model with a local potential similar to 44 Ti [3, 4]. No experimental data that suggest clear α cluster states hampered to conclude that the α cluster picture persists in 52 Ti in the jj-shell closed 48 Ca core region. Very recently Bailey et al.[33] reported that they newly observed α cluster states at the highl...

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“…Our analysis shows these same nuclear refraction effects to be present at much lower energies. A parametrization of the S-matrix given by (1) and (2) is capable of describing quantitatively the observed [20,21,22] intermediate energy a-nucleus angular distributions [23]. At these energies there is no longer an outer barrier in the e-nucleus potential.…”

Section: Discussionmentioning

confidence: 99%

Anomalous large angle alpha scattering

Hartmann¹

1977

Z Physik A

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For e-nucleus potentials which contain a pocket, the scattering matrix may be split into 'barrier' and 'internal' components. Using simple parametrizations for these components, analytic expressions are derived for the corresponding 'barrier' and 'internal' cross sections. The oscillations present in these cross sections are interpreted as arising from interference between various terms in the Poisson summation formula for the scattering amplitudes. At backward angles the 'internal' cross section and the cross sections resulting from various Regge pole models are shown to have the same angular dependence. A method is given to locate roughly the position of the dominant Regge pole of the scattering matrix. At more foreward angles the 'internal' cross section, unlike those from the Regge pole models, describes the nuclear refraction undergone by eparticles that are transmitted through the target. Such refraction effects have previously been invoked to explain intermediate energy c~-nucleus scattering.

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Large angle scattering of 100 MeV α-particles from 40, 44, 48Ca

Cited by 49 publications

References 20 publications

Investigation of large angle structure in ?-scattering from calcium isotopes betweenE ?=36?61 MeV

Investigation of large angle structure in ?-scattering from calcium isotopes betweenE ?=36?61 MeV

Existence of higher nodal band states withα+Ca48cluster structure inTi52

Anomalous large angle alpha scattering

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