Gamow-Teller strength and giant resonances in 90Zr(n,p) at 198 MeV

doi:10.1016/0370-2693(88)90703-4

Physics Letters B

Volume 206, Issue 4, 2 June 1988, Pages 597-600

https://doi.org/10.1016/0370-2693(88)90703-4 Get rights and content

Abstract

The ⁹⁰Zr(n,p)⁹⁰Y reaction has been studied at a bombarding energy of 198 MeV in a search of GT⁺ strength. Up to 10 MeV excitation in ⁹⁰Y, we obtain a firm upper limit of S_β⁺ ⩽ 3.6. The majority of the strength at low excitations is identified as spin dipole.

References (26)

C. Gaarde
Nucl. Phys. A
(1980)
A. Bohr et al.
Phys. Lett. B
(1981)
T.D. Ford
Phys. Lett. B
(1987)
R. Henderson
Nucl. Instrum. Methods A
(1987)
D.C. Kocher
Nucl. Data Sheets
(1975)
W.J. Courtney et al.
At. Nucl. Data Tables
(1975)
C. Gaarde
Nucl. Phys. A
(1981)
I.S. Towner
Nucl. Phys. A
(1985)
S. DroŻdŻ
Nucl. Phys. A
(1986)
C.D. Goodman
Phys. Rev. Lett
(1980)

J. Rapaport

G.F. Bertsch et al.

Phys. Rev. C

(1982)

F. Osterfeld et al.

Phys. Rev. C

(1985)

Cited by (21)

Deeply bound pionic states in heavy nuclei
2012, Physics Reports
The present paper reviews theoretical and experimental studies of a new type of nuclear spectroscopy for the structure of deeply bound $π^{-}$ states and their formation processes through “pion-transfer” nuclear reactions. The calculated energy levels of deeply bound pionic states in heavy nuclei using the standard pion–nucleus optical potential are found to be narrow discrete states even for the $1 s$ state in ²⁰⁸Pb. These hitherto unexpected results are caused by the repulsive pion–nucleus optical potential which pushes pionic wavefunctions outwards so that the nuclear absorption of the bound pions is weakened. Theoretical studies on pion-transfer reactions were carried out as a methodological guide to produce these deeply bound pionic states experimentally. In particular, various predictions were made on the pion-transfer proton-pickup reactions $(n, d)$ and ( $d$ , ³He). Following these theoretical studies successful experiments on high-resolution spectroscopy of ( $d$ , ³He) reactions were carried out at GSI. The experimental procedures and results together with their theoretical implications are also reviewed. The most important feature of deeply bound $1 s$ states of $π^{-}$ in heavy nuclei is that it provides unique information on the $s$ -wave isovector $π^{-} N$ interaction which is connected to reduction of chiral symmetry breaking in the nuclear medium. Recent experiments on Pb and Sn isotopes have yielded clear evidence for partial restoration of chiral symmetry in the nuclear medium.
Isovector giant resonances in 6He, 12B, 90Y, 120In, and 208Tl observed in the (7Li,7Be) charge-exchange reaction
1999, Nuclear Physics A
The (⁷Li,⁷Be) and (⁷Li,⁷Beγ) reactions have been studied at bombarding energies of 50 A MeV on targets of ⁶Li, ¹²C, ⁹⁰Zr, ¹²⁰Sn, ²⁰⁸Pb, and polystyrene. The detection of Doppler-shifted γ-rays from excited ⁷Be permits the identification of the spinflip and non-spinflip characteristics. Transitions to over 20 discrete states and resonances have been observed. Angular distributions for ⁶Li and ¹²C are well described by microscopic one-step distorted-waves calculations with shell-model transition amplitudes. The transitions to the ground states of ⁶He and ¹²C exhibit significant Gamow-Teller strength, but ∼7% and ∼17%, respectively, of the calculated cross sections at θ ≈ 0° arise from the tensor interaction. A broad resonance at ∼5.6 MeV in the halo nucleus ⁶He with J^π = (2⁺,1⁻,0⁺) seems to correspond to a structure predicted at this excitation energy containing soft modes of excitation with J^π = 0⁺and/or 2⁺. A resonance in ¹²B at ∼4.5 MeV is described by a superposition of known 2⁻ and 4⁻ states, and another one at ∼7.5 MeV is dominated by a transition to a 2⁻ state with weaker contributions from two 1⁻ states (spin dipole and giant dipole). Four to six resonances each, mostly spin-dipole resonances, were identified in the final nuclei ⁹⁰Y, ¹²⁰In, and ²⁰⁸Tl. The non-resonant quasi-free charge-exchange reaction p_bound(⁷Li,⁷Be)n_free was observed for all targets up to effective excitation energies of 50 MeV. The mechanism is related to that on free protons. The effective number of participating protons was determined.
Nuclear data sheets for A = 90
1997, Nuclear Data Sheets
Experimental data for all nuclei with mass number A = 90 have been evaluated, and their corresponding level schemes from radioactive decay and reaction studies are presented.
This evaluation shows levels in⁹⁰Tc and⁹⁰Ru from (HI, xpxnγ) reactions seen for the first time, and new levels up to spin J = 25 in⁹⁰Mo. A new precise measurement (93Mi04) of γ rays using the⁸⁹Y(n, γ) reaction provided a complete level scheme for⁹⁰Y, which has superseded that of 83De27.
Cutoff Date:All data received by May 1, 1997 were evaluated.
General Policies and Organization of Material:See the January issue of Nuclear Data Sheets.
The orbital magnetic dipole response of nonspherical nuclei
1996, Nuclear Physics A
We discuss experimental facts and theoretical models of the isovector M1 response in nuclei. The three isospin components (T₂ = −1, 0, 1), orbital and spin components are identified and introduced by isospin decomposition of the nuclear M1 operator. Microscopic descriptions of the low-lying orbital ΔT₂ = 0 excitation are given. The collective interpretation of this mode is discussed in some detail with the conclusion that though it is an isovector rotational oscillation, a small but important shape vibrational admixture is present, allowing rotation without separation of the proton and neutron densities, in contrast to the scissors mode visualization.
Nuclear data sheets for A = 90
1992, Nuclear Data Sheets
The 90Zr(n, p)90Y reaction at E<inf>n</inf>=98 MeV
1992, Nuclear Physics, Section A
Double-differential cross sections of the ⁹⁰Zr(n, p) reaction have been measured at 98 MeV in the angular range 0°–30° for excitation energies up to 40 MeV. The spectra have been interpreted in terms of direct and multistep reactions. The contributions from the latter have been calculated using a statistical theory of multistep direct reactions. The direct parts of the spectra have been decomposed into their different multipole components by using peak-fitting and multipole-decomposition techniques, based on sample angular distributions calculated within the distorted-wave Born approximation. An extensive microscopic calculation based on the random-phase approximation has also been performed and the results are compared with the experimental data. A value S_β⁺ = 1.7±0.2 is extracted for the Gamow-Teller strength, suggesting an occupancy ν² = 0.09±0.01 for the $1 g_{92}$ proton orbital. This value has been compared with recent results from (d, ³He) proton pickup and (e, e′p) knockout reactions.

View all citing articles on Scopus

^☆: This research is supported in part by the Natural Sciences and Engineering Research Council of Canada, and by the Australian Research Grants Scheme.

View full text

Article preview

Physics Letters B

Abstract

References (26)

Nucl. Phys. A

Phys. Lett. B

Phys. Lett. B

Nucl. Instrum. Methods A

Nucl. Data Sheets

At. Nucl. Data Tables

Nucl. Phys. A

Nucl. Phys. A

Nucl. Phys. A

Phys. Rev. Lett

Phys. Rev. C

Phys. Rev. C

Cited by (21)

Deeply bound pionic states in heavy nuclei

Isovector giant resonances in <sup>6</sup>He, <sup>12</sup>B, <sup>90</sup>Y, <sup>120</sup>In, and <sup>208</sup>Tl observed in the (<sup>7</sup>Li,<sup>7</sup>Be) charge-exchange reaction

Nuclear data sheets for A = 90

The orbital magnetic dipole response of nonspherical nuclei

Nuclear data sheets for A = 90

The <sup>90</sup>Zr(n, p)<sup>90</sup>Y reaction at E<inf>n</inf>=98 MeV

Physics Letters B

Gamow-Teller strength and giant resonances in 90Zr(n,p) at 198 MeV☆

Abstract

Nucl. Phys. A

Phys. Lett. B

Phys. Lett. B

Nucl. Instrum. Methods A

Nucl. Data Sheets

At. Nucl. Data Tables

Nucl. Phys. A

Nucl. Phys. A

Nucl. Phys. A

Phys. Rev. Lett

Phys. Rev. C

Phys. Rev. C

Deeply bound pionic states in heavy nuclei

Isovector giant resonances in <sup>6</sup>He, <sup>12</sup>B, <sup>90</sup>Y, <sup>120</sup>In, and <sup>208</sup>Tl observed in the (<sup>7</sup>Li,<sup>7</sup>Be) charge-exchange reaction

Nuclear data sheets for A = 90

The orbital magnetic dipole response of nonspherical nuclei

Nuclear data sheets for A = 90

The <sup>90</sup>Zr(n, p)<sup>90</sup>Y reaction at E<inf>n</inf>=98 MeV

Gamow-Teller strength and giant resonances in ⁹⁰Zr(n,p) at 198 MeV☆