Direct Experimental Evidence for a Soft-Dipole Response in
                    <sup>6</sup>
                    He

Sakuta, S.B.; Ogloblin, A. A.; Osadchy, O.; Glukhov, Yu.A.; Ershov, S. N.; Gareev, F.A.; Vaagen, J. S.

doi:10.1209/0295-5075/22/7/006

Cited by 24 publications

(18 citation statements)

References 18 publications

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“…As a result, we get a flat total distribution extending over a rather wide angular range on the high-energy slope of the second bump. These results are in qualitative agreement with experimental data on the 6 Li( 7 Li, 7 Be) 6 He * reaction [27,28] if we scale angular distribution according to the transferred momentum q.…”

Section: Fixed Excitation Energysupporting

confidence: 90%

Halo excitation of6He in inelastic and charge-exchange reactions

et al. 1997

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Four-body distorted wave theory appropriate for nucleon-nucleus reactions leading to 3-body continuum excitations of two-neutron Borromean halo nuclei is developed. The peculiarities of the halo bound state and 3-body continuum are fully taken into account by using the method of hyperspherical harmonics. The procedure is applied for A = 6 test-bench nuclei; thus we report detailed studies of inclusive cross sections for inelastic 6 He(p,p ′ ) 6 He * and charge-exchange 6 Li(n,p) 6 He * reactions at nucleon energy 50 MeV. The theoretical low-energy spectra exhibit two resonance-like structures. The first (narrow) is the excitation of the well-known 2 + three-body resonance. The second (broad) bump is a composition of overlapping soft modes of multipolarities 1 − , 2 + , 1 + , 0 + whose relative weights depend on transferred momentum and reaction type. Inelastic scattering is the most selective tool for studying the soft dipole excitation mode.Recent success in developing experimental methods for dripline nuclei, that in particular allow exploration of halo phenomena in light nuclei, has put on the agenda a need for appropriate theoretical methods which take into account the peculiarities of weakly bound and spatially extended systems. For Borromean two-neutron halo nuclei ( 6 He, 11 Li, etc.) an understanding of the essential halo structure has been obtained in the framework of 3-body models [1]. Reactions involving these nuclei present however, at least a 4-body problem. The direct solution of 4-body systems is extremely difficult, and approximate methods are required. For high energy elastic scattering and relativistic fragmentation of Borromean halo nuclei, a 4-body Glauber method has been developed [2,3]. For Coulomb breakup or electromagnetic dissociation (EMD) the first order (Alder-Winther) perturbation theory or an equivalent semiclassical treatment [4] has been used, but with exact 3-body continuum wave functions [5][6][7]. Also for the (anti)neutrino induced reactions on 6 Li populating the 6 He and 6 Be 3-body continua, have proper final state wave functions recently been used [8].The most reliable information on properties of halo nuclei, especially for the low-lying part of excitation spectra, is experimentally obtainable by intermediate energy elastic and inelastic scattering and charge-exchange reactions. The distorted wave theory is the most common way to analyse such processes [9], but for halo systems their spatial granularity as well as peculiarities of their quantum structure have to be taken into account. The 3-body interaction dynamics defines the low-lying part of excitation spectra, in particular the soft modes of Borromean systems, and has to be treated properly. Until now, only the hyperspherical harmonics (HH) method [10] is able to provide a formulation of the scattering theory to the 3-body Borromean continuum. The Faddeev equations technique [11] has been developed to investigate breakup of 3-nucleon systems, but has hitherto not been applied to investigate the continuum in Borromean...

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Section: Fixed Excitation Energysupporting

confidence: 90%

Halo excitation of6He in inelastic and charge-exchange reactions

et al. 1997

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“…In each case, the spectra are compared with (y, n) spectra on the same target that have been shifted according to the reaction Q [5,50]. Recently, Sakuta et al [9]reported that three resonances around E = 6, 12, and 20 MeV are observed in He from the 6Li(7Li, 7Be)6He reaction at a beam energy of 82 MeV [9].…”

Section: A Mda Resultsmentioning

confidence: 99%

Dipole excitations inp-shell nuclei via (p,n) reactions

et al. 1995

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Using the neutron time-of-flight facility at the Indiana University Cyclotron Facility we have studied (p, n) reactions on the light nuclei Li, ' "B,and ' ' C. Double differential cross sections have been measured between Hi, b=0' and 50' in 5' intervals, at E"=186MeV. Contributions of the quasifree reaction in the giant resonance region are estimated. Energy spectra of EL=1 transitions have been extracted using multipole decomposition analysis. The resulting EL=1 spectra are compared with results of photonuclear reactions.Empirical results are also compared with distorted wave impulse approximation calculations. PACS number(s): 25.40.Ep, 27.20.+n, 24.70.+s

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“…Experimental investigations on the soft DR in 6 He have been carried out by using various reactions [5][6][7][8][9]. In ͑n, p͒-like charge exchange reactions on 6 Li [5-7], a broad resonancelike structure was observed at an excitation energy of E x ϳ 7 MeV where an analog of the GDR is expected to be excited.…”

Section: (Received 30 November 1999)mentioning

confidence: 99%

“…In ͑n, p͒-like charge exchange reactions on 6 Li [5-7], a broad resonancelike structure was observed at an excitation energy of E x ϳ 7 MeV where an analog of the GDR is expected to be excited. Sakuta et al [5] showed evidence for a resonance with DL 1 at E x ϳ 6 MeV in the ͑ 7 Li, 7 Be͒ reaction at a low incident energy of 82 MeV.…”

Section: (Received 30 November 1999)mentioning

confidence: 99%

Soft Dipole Resonance in the Neutron-Skin NucleusH6e

et al. 2000

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A candidate for a soft dipole resonance, a dipole oscillation mode between a core cluster and a neutron skin, was observed at Ex = 4+/-1 MeV and with a width of 4+/-1 MeV in 6He via the 6Li( 7Li, 7Be) reaction at an incident energy of 65A MeV and forward scattering angles including 0 degrees. Its cross section is deduced to be sigma(0 degrees ) = 0.9+/-0.2 mb/sr. This value is comparable to that of the giant dipole resonance simultaneously measured.

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Direct Experimental Evidence for a Soft-Dipole Response in ⁶ He

Abstract: The differential cross-sections of the charge exchange reaction 6Li(7Li, 7Be) 6He

Cited by 24 publications

References 18 publications

Halo excitation of6He in inelastic and charge-exchange reactions

Halo excitation of6He in inelastic and charge-exchange reactions

Dipole excitations inp-shell nuclei via (p,n) reactions

Soft Dipole Resonance in the Neutron-Skin NucleusH6e

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Direct Experimental Evidence for a Soft-Dipole Response in 6 He

Abstract: The differential cross-sections of the charge exchange reaction 6Li(7Li, 7Be) 6He

Cited by 24 publications

References 18 publications

Halo excitation of6He in inelastic and charge-exchange reactions

Halo excitation of6He in inelastic and charge-exchange reactions

Dipole excitations inp-shell nuclei via (p,n) reactions

Soft Dipole Resonance in the Neutron-Skin NucleusH6e

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Product

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Direct Experimental Evidence for a Soft-Dipole Response in ⁶ He