High-resolution study of the $^{9}\mathrm{Be}$($^{3}\mathrm{He}$,$t$)$^{9}\mathrm{B}$ reaction up to the $^{9}\mathrm{B}$ triton threshold

High-resolution study of the ${}^{9}{Be}$ ( ${}^{3}{He}$ , $t$ ) ${}^{9}B$ reaction up to the ${}^{9}B$ triton threshold

C. Scholl, Y. Fujita, T. Adachi, P. von Brentano, H. Fujita, M. Górska, H. Hashimoto, K. Hatanaka, H. Matsubara, K. Nakanishi, T. Ohta, Y. Sakemi, Y. Shimbara, Y. Shimizu, Y. Tameshige, A. Tamii, M. Yosoi, and R. G. T. Zegers

Phys. Rev. C 84, 014308 – Published 12 July 2011

Abstract

A high-energy-resolution ${}^{9}{Be}$ ( ${}^{3}{He}$ , $t$ ) ${}^{9}B$ charge-exchange reaction was performed around a scattering angle of $0^{°}$ and at an intermediate incident energy of 140 MeV/nucleon for the study of precise Gamow-Teller (GT) transition strengths. The energy resolution of 30 keV allowed a precise deconvolution of the spectrum and the determination of angular distributions of cross sections, excitation energies, and decay widths. The GT strength of 10 states has been determined for the first time using the GT strength of the analogous $β$ decays of ${}^{9}{Li}$ and ${}^{9}C$ as standards. The large difference between the GT strengths going to the low-lying $T = 1 / 2$ and the highly excited $T = 3 / 2$ states is interpreted as a result of their different spatial structures. The obtained GT strength distribution is compared to the results of a ( $p$ , $n$ ) experiment with lower resolution performed in the 1980s. In particular, the width of the 16.8 MeV, $J^{π} = (5 / 2^{+}$ ) state has been determined for the first time.

Received 28 March 2011

DOI:https://doi.org/10.1103/PhysRevC.84.014308

Authors & Affiliations

C. Scholl^1,*, Y. Fujita², T. Adachi^2,3,†, P. von Brentano^1,‡, H. Fujita², M. Górska⁴, H. Hashimoto⁵, K. Hatanaka⁵, H. Matsubara^5,6, K. Nakanishi⁶, T. Ohta⁵, Y. Sakemi^5,7, Y. Shimbara^8,9, Y. Shimizu⁵, Y. Tameshige⁵, A. Tamii⁵, M. Yosoi^10,5, and R. G. T. Zegers^8,11

¹Institut für Kernphysik, Universität zu Köln, 50937 Köln, Germany
²Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan
³Kernfysisch Versneller Instituut, 9747 AA Groningen, The Netherlands
⁴GSI Helmholtzzentrum für Schwerionenforschung GmbH, D-64291 Darmstadt, Germany
⁵Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047, Japan
⁶Center for Nuclear Study, University of Tokyo, RIKEN Campus, Wako, Tokyo 351-0198, Japan
⁷CYRIC, Tohoku University, Sendai, Japan
⁸NSCL, Michigan State University, East Lansing, Michigan 48824-1321, USA
⁹RIKEN Nishina Center, Wako, Tokyo 351-0198, Japan
¹⁰Department of Physics, Kyoto University, Sakyo, Kyoto 606-8502, Japan
¹¹Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA

^*scholl@ikp.uni-koeln.de
^†Current adress: Research Center for Electron and Photon Science, Tohoku University, Sendai, Japan.
^‡brentano@ikp.uni-koeln.de

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 84, Iss. 1 — July 2011

Reuse & Permissions

Access Options

Article Available via CHORUS

Download Accepted Manuscript

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
Spectrum of the ${}^{9}{Be}$ ( ${}^{3}{He}$ , $t$ ) ${}^{9}B$ reaction at 140 MeV/nucleon beam energy and at scattering angles $Θ ⩽ 0 . 5^{°}$ . (a) The full spectrum without any cutoffs. The only prominent peaks are the two $T = 1 / 2$ , $J^{π} = 3 / 2^{-}$ (ground state), and $J^{π} = 5 / 2^{-}$ (2.4 MeV) states. (b) The same spectrum with a cutoff at 3000 counts. Weakly excited states at higher excitation energies become visible. The two $T = 3 / 2$ states at 14.65 MeV ( $J^{π} = 3 / 2^{-}$ ) and 17.1 MeV ( $J^{π} = 1 / 2^{-}$ ) are marked in the figure.Reuse & Permissions
Figure 2
Deconvolution of the energy spectrum of the ${}^{9}{Be}$ ( ${}^{3}{He}$ , $t$ ) ${}^{9}B$ reaction at 140 MeV/nucleon beam energy, with the scattering angle $Θ ⩽ 0 . 5^{°}$ . The spectrum has been subdivided in three excitation energy regions for better visibility. In the first spectrum, the ground-state peak was cut off (the maximum lies at $\approx$ 1 20 000 counts). The peaks have been deconvoluted using Lorentzian shapes folded with a spectrometer-specific reponse function. All peaks have numbered labels corresponding to their excitation energy, which are also used in Table .Reuse & Permissions
Figure 3
Angular distribution of cross sections around the zero-degree scattering angle of states excited with $Δ ℓ = 0$ . The line is the angular distribution calculated in DWBA, multiplied for each state by a single scaling factor, which is used to extrapolate the cross section at the zero-degree scattering angle from the experimental cross sections. For the $T = 3 / 2$ states, the DWBA parameters were changed to obtain a good fit to the experimental data. The differential cross sections were calculated using Eq. (8). As mentioned in the text, the error bars include only the statistical errors arising from the deconvolution of the spectrum.Reuse & Permissions
Figure 4
The $A = 9$ isobar diagram. The arrows show the start and end point as well as the direction of the transitions ${}^{9}{Li}$ ( $β^{-}$ ) ${}^{9}{Be}$ , ${}^{9}{Be}$ ( ${}^{3}{He}$ , $t$ ) ${}^{9}B$ , and ${}^{9}C$ ( $β^{+}$ ) ${}^{9}B$ . Adapted from Ref.[26]. The diagrams for individual isobars are shifted vertically to eliminate the neutron-proton mass difference and the Coulomb energy. The energies in square brackets represent the approximate nuclear energy $E_{N} = M (Z, A) - Z M (H) - N M (n) - E_{C}$ , minus the corresponding quantity for ${}^{9}{Be}$ .Reuse & Permissions
Figure 5
(a) Distribution of $B$ (GT) strengths obtained from the ${}^{9}{Be}$ ( ${}^{3}{He}$ , $t$ ) ${}^{9}B$ charge-exchange reaction studied in this work. Transitions to low-lying states in ${}^{9}B$ have large GT strength, whereas the transitions to the highly excited states in ${}^{9}B$ have very small GT strengths. The $B$ (GT) values of all observed GT transitions, including the weak transition strengths indicated by arrows, are given in Table . (b) The same pattern is seen in the “reverse” transition, which shows the distribution of $B$ (GT) strengths obtained from the $β^{+}$ decay of ${}^{9}C$ (data from Refs.[26, 34, 35]). The ${}^{9}C$ $β^{+}$ decay exhibits strong GT transitions to the highly excited states in ${}^{9}B$ , and weak GT transition strengths to the low-lying states. See the $A = 9$ isobar diagram in Fig. 4 for the energy difference and the starting and end points of the respective transitions.Reuse & Permissions
Figure 6
Illustration of the spatial shapes in the $A = 9$ system and interpretation of the distribution of $B$ (GT) strengths in charge-exchange processes in the $A = 9$ system (see Figs. 4 and 5). The ground states of ${}^{9}{Li}$ and ${}^{9}C$ can be considered spherical or mean-field like and have closed $p_{3 / 2}$ shells, while the ground states of ${}^{9}{Be}$ and ${}^{9}B$ are strongly deformed and have a 2 $α +$ $n$ or 2 $α +$ $p$ cluster structure. The weak process, mediated by the $σ τ$ operator, connects states with very different spatial structure only very weakly. Transitions that have a large $B$ (GT) value are marked with a thick arrow, while transitions with small $B$ (GT) values are marked with a thin arrow.Reuse & Permissions

Physical Review C

covering nuclear physics

High-resolution study of the ${}^{9}{Be}$ ( ${}^{3}{He}$ , $t$ ) ${}^{9}B$ reaction up to the ${}^{9}B$ triton threshold

C. Scholl, Y. Fujita, T. Adachi, P. von Brentano, H. Fujita, M. Górska, H. Hashimoto, K. Hatanaka, H. Matsubara, K. Nakanishi, T. Ohta, Y. Sakemi, Y. Shimbara, Y. Shimizu, Y. Tameshige, A. Tamii, M. Yosoi, and R. G. T. Zegers

Phys. Rev. C 84, 014308 – Published 12 July 2011

Abstract

Authors & Affiliations

Article Text (Subscription Required)

References (Subscription Required)

Issue

Access Options

Physical Review C

covering nuclear physics

High-resolution study of the Be9(He3,t)B9 reaction up to the B9 triton threshold

C. Scholl, Y. Fujita, T. Adachi, P. von Brentano, H. Fujita, M. Górska, H. Hashimoto, K. Hatanaka, H. Matsubara, K. Nakanishi, T. Ohta, Y. Sakemi, Y. Shimbara, Y. Shimizu, Y. Tameshige, A. Tamii, M. Yosoi, and R. G. T. Zegers

Phys. Rev. C 84, 014308 – Published 12 July 2011

Abstract

Authors & Affiliations

Article Text (Subscription Required)

References (Subscription Required)

Issue

Access Options

Authorization Required

Other Options

Download & Share

Images

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Log In

Search

Article Lookup

Paste a citation or DOI

Enter a citation

High-resolution study of the ${}^{9}{Be}$ ( ${}^{3}{He}$ , $t$ ) ${}^{9}B$ reaction up to the ${}^{9}B$ triton threshold