-
M Sasano,
G Perdikakis,
R G T Zegers,
Sam M Austin,
D Bazin,
B A Brown,
C Caesar,
A L Cole,
J M Deaven,
N Ferrante, [......],
R Meharchand,
F Montes,
J Palardy,
A Prinke, L A Riley,
H Sakai,
M Scott,
A Stolz,
L Valdez,
K Yako
[show abstract]
[hide abstract]
ABSTRACT: A new technique to measure (p,n) charge-exchange reactions in inverse kinematics at intermediate energies on unstable isotopes was successfully developed and used to study the (56)Ni(p,n) reaction at 110 MeV/u. Gamow-Teller transition strengths from (56)Ni leading to (56)Cu were obtained and compared with shell-model predictions in the pf shell using the KB3G and GXPF1A interactions. The calculations with the GXPF1A interaction reproduce the experimental strength distribution much better than the calculations that employed the KB3G interaction, indicating deficiencies in the spin-orbit and proton-neutron residual potentials for the latter. The results are important for improving the description of electron-capture rates on nuclei in the iron region, which are important for modeling the late evolution of core-collapse and thermonuclear supernovae.
Physical Review Letters 11/2011; 107(20):202501. · 7.37 Impact Factor
-
L. A. Riley,
P. Adrich,
T. R. Baugher,
D. Bazin,
B. A. Brown,
J. M. Cook,
P. D. Cottle,
C. Aa. Diget,
A. Gade,
D. A. Garland,
T. Glasmacher,
K. E. Hosier,
K. W. Kemper,
A. Ratkiewicz,
K. P. Siwek,
J. A. Tostevin,
D. Weisshaar
[show abstract]
[hide abstract]
ABSTRACT: The recent assertion that shape coexistence occurs in the neutron-rich isotope 43S implies that a state observed at 940 keV in a previous study is a rotational excitation of the deformed ground state. Here we use results from two intermediate-energy reactions to demonstrate that this state—assigned an energy of 971 keV in the present work—is indeed a rotational state. This result strengthens the case for shape coexistence in 43S.
Phys. Rev. C. 09/2009; 80(3).
-
S. Ettenauer,
H. Zwahlen,
P. Adrich,
D. Bazin,
C. M. Campbell,
J. M. Cook,
A. D. Davies,
D.-C. Dinca,
A. Gade,
T. Glasmacher,
J.-L. Lecouey,
W. F. Mueller,
T. Otsuka,
R. R. Reynolds, L. A. Riley,
J. R. Terry,
Y. Utsuno,
K. Yoneda
[show abstract]
[hide abstract]
ABSTRACT: The neutron-rich nucleus 30Na in the vicinity of the “Island of Inversion” was investigated using intermediate-energy Coulomb excitation. A single γ-ray transition was observed and attributed to the 31+→2gs+ decay. A transition probability of B(E2;2gs+→31+)=147(21) e2 fm4 was determined and found in agreement with a previous experiment and with large-scale shell-model calculations. Evidence for the strong excitation of the 41+ state predicted by the shell-model calculations was not observed.
Phys. Rev. C. 07/2008; 78(1).
-
A Gade,
P Adrich,
D. Bazin,
M D Bowen,
B A Brown,
C M Campbell,
J M Cook,
T. Glasmacher,
K Hosier,
S McDaniel,
D McGlinchery,
A. Obertelli, L A Riley,
K Siwek,
J A Tostevin,
D. Weisshaar
[show abstract]
[hide abstract]
ABSTRACT: We report on the first in-beam $\gamma$-ray spectroscopy of \nuc{23}{Al} using two different reactions at intermediate beam energies: inelastic scattering off \nuc{9}{Be} and heavy-ion induced one-proton pickup, \nuc{9}{Be}(\nuc{22}{Mg},\nuc{23}{Al}$+\gamma$)X, at 75.1 MeV/nucleon. A $\gamma$-ray transition at 1616(8) keV -- exceeding the proton separation energy by 1494 keV -- was observed in both reactions. From shell model and proton decay calculations we argue that this $\gamma$-ray decay proceeds from the core-excited $7/2^+$ state to the $5/2^+$ ground state of \nuc{23}{Al}. The proposed nature of this state, $[\nuc{22}{Mg}(2^+_1) \otimes \pi d_{5/2}]_{7/2+}$, is consistent with the presence of a gamma-branch and with the population of this state in the two reactions. Comment: Physics Letters B, accepted
07/2008;
-
A. Gade,
P. Adrich,
D. Bazin,
M. D. Bowen,
B. A. Brown,
C. M. Campbell,
J. M. Cook,
T. Glasmacher,
K. Hosier,
S. McDaniel,
D. McGlinchery,
A. Obertelli, L. A. Riley,
K. Siwek,
D. Weisshaar
[show abstract]
[hide abstract]
ABSTRACT: We report on the first determination of the 21+ energy of 20Mg, the most neutron-deficient Mg isotope known to exist. The result, E(21+)=1598(10) keV, obtained from in-beam γ-ray spectroscopy following the two-neutron removal from a 22Mg secondary beam, is discussed in the framework of the isobaric mass multiplet equation (IMME). Resulting predictions for the excitation energies of the T=2,2+ states in the 20F and 20Na isobars are presented. The mirror energy difference, E(21+,20Mg)-E(21+,20O)=-77(10) keV, is compared to a recent prediction within the nuclear shell model based on the “USDm - gap Z14<” modification of the universal sd (USD) effective interaction.
Phys. Rev. C. 08/2007; 76(2).
-
A. Gade,
B. A. Brown,
D. Bazin,
C. M. Campbell,
J. A. Church,
D. C. Dinca,
J. Enders,
T. Glasmacher,
M. Horoi,
Z. Hu,
K. W. Kemper,
W. F. Mueller,
T. Otsuka, L. A. Riley,
B. T. Roeder,
T. Suzuki,
J. R. Terry,
K. L. Yurkewicz,
H. Zwahlen
[show abstract]
[hide abstract]
ABSTRACT: The energy of the first excited state in the neutron-rich N=28 nucleus 45Cl has been established via in-beam γ-ray spectroscopy following proton removal. This energy value completes the systematics of the E(1/21+)-E(3/21+) level spacing in odd-mass K, Cl, and P isotopes for N=20-28. The results are discussed in the framework of shell-model calculations in the sd-fp model space. The contribution of the central, spin-orbit, and tensor components is discussed from a calculation based on a proton single-hole spectrum from G-matrix and π+ρ meson exchange potentials. A composite model for the proton 0d3/2-1s1/2 single-particle energy shift is presented.
Phys. Rev. C. 09/2006; 74(3).
-
A Gade,
B A Brown,
D Bazin,
C M Campbell,
J A Church,
D C Dinca,
J Enders,
T Glasmacher,
M Horoi,
Z Hu,
K W Kemper,
W F Mueller,
T Otsuka, L A Riley,
B T Roeder,
T Suzuki,
J R Terry,
K L Yurkewicz,
H Zwahlen
[show abstract]
[hide abstract]
ABSTRACT: The energy of the first excited state in the neutron-rich N=28 nucleus 45Cl has been established via in-beam γ-ray spectroscopy following proton removal. This energy value completes the systematics of the E(1/21+)-E(3/21+) level spacing in odd-mass K, Cl, and P isotopes for N=20-28. The results are discussed in the framework of shell-model calculations in the sd-fp model space. The contribution of the central, spin-orbit, and tensor components is discussed from a calculation based on a proton single-hole spectrum from G-matrix and π+ρ meson exchange potentials. A composite model for the proton 0d3/2-1s1/2 single-particle energy shift is presented.
Physical Review C. 01/2006; 74(3):034322 1-5.
-
J. A. Church,
C. M. Campbell,
D.-C. Dinca,
J. Enders,
A. Gade,
T. Glasmacher,
Z. Hu,
R. V. F. Janssens,
W. F. Mueller,
H. Olliver,
B. C. Perry, L. A. Riley,
K. L. Yurkewicz
[show abstract]
[hide abstract]
ABSTRACT: The degree of collectivity in the neutron-rich nuclei 32Mg and 34Mg has been determined via intermediate-energy Coulomb excitation in inverse kinematics. Measured energies of the first excited 2+ states and reduced electric quadrupole transition probabilities B(E2;0g.s.+→21+) are presented for 32Mg and 34Mg. The results agree with previous measurements and confirm the placement of both nuclei within the “island of inversion.”
Phys. Rev. C. 11/2005; 72(5).
-
A Gade,
D Bazin,
B A Brown,
C M Campbell,
J A Church,
D-C Dinca,
J Enders,
T Glasmacher,
P G Hansen,
M Honma,
T Mizusaki,
W F Mueller,
H Olliver,
T Otsuka, L A Riley,
J R Terry,
J A Tostevin,
K L Yurkewicz
[show abstract]
[hide abstract]
ABSTRACT: Quadrupole collectivity in the proximity of the doubly-magic shell closure at N = Z = 28 has been studied using intermediate-energy Coulomb excitation of 54,56,58Ni and 52Fe. The results will be summarized and discussed in comparison to large-scale shell model calculations. A complementary experimental approach sensitive to the single-particle structure of exotic nuclei, one-neutron knockout at intermediate beam energies, has been applied to the proton-rich N = 16 isotones 34Ar, 33Cl and 32S as well as to 32Ar where the knockout residue 31Ar is the last particle-bound Z = 18 isotope. The reduction of single-particle strength (''quenching'') compared to shell-model calculations using the USD interaction is discussed in the framework of correlation effects beyond effective-interaction theory.
Journal of Physics Conference Series 09/2005; 20(1):95.
-
L. A. Riley,
M. A. Abdelqader,
D. Bazin,
M. J. Bojazi,
B. A. Brown,
C. M. Campbell,
J. A. Church,
P. D. Cottle,
D. -C. Dinca,
J. Enders, [......],
Z. Hu,
K. W. Kemper,
W. F. Mueller,
H. Olliver,
T. Otsuka,
B. C. Perry,
B. T. Roeder,
B. M. Sherrill,
T. P. Spencer,
J. R. Terry
[show abstract]
[hide abstract]
ABSTRACT: Low-lying excited states of 46Ar have been studied via inverse-kinematics proton scattering with a thick target. Coupled-channels calculations have been used to extract the deformation length of the 21+ state. This result, combined with existing Coulomb excitation data, yields a ratio of the neutron-to-proton transition matrix elements of Mn/Mp=1.19(25)N/Z, showing a departure from the proton dominance observed in the N=28 isotones above 48Ca. The status of the N=28 shell below 48Ca is discussed.
Phys. Rev. C. 08/2005; 72(2).
-
J A Church,
C M Campbell,
D C Dinca,
J Enders,
A Gade,
T Glasmacher,
Z Hu,
R V F Janssens,
W F Mueller,
H Olliver,
B C Perry, L A Riley,
K L Yurkewicz
[show abstract]
[hide abstract]
ABSTRACT: The degree of collectivity in the neutron-rich nuclei 32Mg and 34Mg has been determined via intermediate-energy Coulomb excitation in inverse kinematics. Measured energies of the first excited 2+ states and reduced electric quadrupole transition probabilities B(E2;0g.s.+→21+) are presented for 32Mg and 34Mg. The results agree with previous measurements and confirm the placement of both nuclei within the “island of inversion.”
Physical Review C. 01/2005; 72(5):054320 1-6.
-
L A Riley,
M A Abdelqader,
D Bazin,
M J Bojazi,
B A Brown,
C M Campbell,
J A Church,
P D Cottle,
D C Dinca,
J Enders, [......],
Z Hu,
K W Kemper,
W F Mueller,
H Olliver,
T Otsuka,
B C Perry,
B T Roeder,
B M Sherrill,
T P Spencer,
J R Terry
[show abstract]
[hide abstract]
ABSTRACT: Low-lying excited states of 46Ar have been studied via inverse-kinematics proton scattering with a thick target. Coupled-channels calculations have been used to extract the deformation length of the 21+ state. This result, combined with existing Coulomb excitation data, yields a ratio of the neutron-to-proton transition matrix elements of Mn/Mp=1.19(25)N/Z, showing a departure from the proton dominance observed in the N=28 isotones above 48Ca. The status of the N=28 shell below 48Ca is discussed.
Physical Review C. 01/2005; 72(2):024311 1-7.
-
A. Gade,
D. Bazin,
B. A. Brown,
C. M. Campbell,
J. A. Church,
D.-C. Dinca,
J. Enders,
T. Glasmacher,
P. G. Hansen,
Z. Hu,
K. W. Kemper,
W. F. Mueller,
H. Olliver,
B. C. Perry, L. A. Riley,
B. T. Roeder,
B. M. Sherrill,
J. R. Terry,
J. A. Tostevin,
K. L. Yurkewicz
[show abstract]
[hide abstract]
ABSTRACT: One-neutron knockout at intermediate beam energies, an experimental approach sensitive to the single-particle structure of
exotic nuclei, has been applied to the well-bound N = 16 isotones 34Ar, 33Cl and 32S as well as to the N = 14 nucleus 32Ar where the knockout residue 31Ar is located at the proton drip line. The reduction of single-particle strength compared to USD shell-model calculations
is discussed in the framework of correlation effects beyond the effective-interaction theory employed in the shell-model approach.
12/2004: pages 251-253;
-
K. L. Yurkewicz,
D. Bazin,
B. A. Brown,
C. M. Campbell,
J. A. Church,
D.-C. Dinca,
A. Gade,
T. Glasmacher,
M. Honma,
T. Mizusaki,
W. F. Mueller,
H. Olliver,
T. Otsuka, L. A. Riley,
J. R. Terry
[show abstract]
[hide abstract]
ABSTRACT: The collectivity of the odd-mass nucleus 55Ni was explored via intermediate-energy Coulomb excitation using a powerful combination of particle and γ-ray spectroscopy. A γ-ray at 2879(18) keV was observed and is interpreted to deexcite a member of the core-coupled quintuplet 21+(56Ni)⊗νf7∕2−1 at the same energy. By similarity with the mirror nucleus 55Co, transition probabilities were calculated assuming Jπ=9∕2− and Jπ=11∕2− for this state. Both assumptions lead to a transition strength higher than predicted by a large-scale shell-model calculation using the GXPF1 effective interaction and exceed the value predicted within a simple weak-coupling approach.
Phys. Rev. C. 12/2004; 70(6).
-
K. L. Yurkewicz,
D. Bazin,
B. A. Brown,
C. M. Campbell,
J. A. Church,
D. C. Dinca,
A. Gade,
T. Glasmacher,
M. Honma,
T. Mizusaki,
W. F. Mueller,
H. Olliver,
T. Otsuka, L. A. Riley,
J. R. Terry
[show abstract]
[hide abstract]
ABSTRACT: The isotopes 54Ni, 56Ni, and 58Ni have been studied via intermediate-energy Coulomb excitation at the National Superconducting Cyclotron Laboratory. Absolute B(E2;01+→21+) excitation strengths have been determined for all three nuclei using a consistent experimental approach, and a measure of quadrupole collectivity has been established in the vicinity of the much discussed doubly magic shell closure at N=Z=28. The energy of and excitation strength to the first 2+ state of 54Ni have been observed for the first time. The results are compared to large-scale shell-model calculations that predict that the E2 strength in 54Ni should be divided between the first and second 2+ states.
Phys. Rev. C. 11/2004; 70(5).
-
A Gade,
D Bazin,
B A Brown,
C M Campbell,
J A Church,
D C Dinca,
J Enders,
T Glasmacher,
P G Hansen,
Z Hu,
K W Kemper,
W F Mueller,
H Olliver,
B C Perry, L A Riley,
B T Roeder,
B M Sherrill,
J R Terry,
J A Tostevin,
K L Yurkewicz
[show abstract]
[hide abstract]
ABSTRACT: The 9Be(32Ar, 31Ar)X reaction, leading to the 5/2+ ground state of a nucleus at the proton drip line, has a cross section of 10.4(13) mb at a beam energy of 65.1 MeV/nucleon. This translates into a spectroscopic factor that is only 24(3)% of that predicted by the many-body shell-model theory. We introduce refinements to the eikonal reaction theory used to extract the spectroscopic factor to clarify that this very strong reduction represents an effect of nuclear structure. We suggest that it reflects correlation effects linked to the high neutron separation energy (22.0 MeV) for this state.
Physical Review Letters 08/2004; 93(4):042501. · 7.37 Impact Factor
-
A Gade,
D Bazin,
B A Brown,
C M Campbell,
J A Church,
D C Dinca,
J Enders,
T Glasmacher,
P G Hansen,
Z Hu,
K W Kemper,
W F Mueller,
H Olliver,
B C Perry, L A Riley,
B T Roeder,
B M Sherrill,
J R Terry,
J A Tostevin,
K L Yurkewicz
[show abstract]
[hide abstract]
ABSTRACT: The 9Be(32Ar,31Ar)X reaction, leading to the 5/2+ ground state of a nucleus at the proton drip line, has a cross section of 10.4(13) mb at a beam energy of 65.1 MeV/nucleon. This translates into a spectroscopic factor that is only 24(3)% of that predicted by the many-body shell-model theory. We introduce refinements to the eikonal reaction theory used to extract the spectroscopic factor to clarify that this very strong reduction represents an effect of nuclear structure. We suggest that it reflects correlation effects linked to the high neutron separation energy (22.0 MeV) for this state.
Physical Review Letters 01/2004; 93(4):042501 1-4. · 7.37 Impact Factor
-
A. Gade,
D. Bazin,
C. M. Campbell,
J. A. Church,
D. C. Dinca,
J. Enders,
T. Glasmacher,
Z. Hu,
K. W. Kemper,
W. F. Mueller,
H. Olliver,
B. C. Perry, L. A. Riley,
B. T. Roeder,
B. M. Sherrill,
J. R. Terry
[show abstract]
[hide abstract]
ABSTRACT: Intermediate-energy Coulomb excitation is a key method to investigate
collectivity in exotic nuclei far from β stability. We report on
the measurement of the absolute
B(E2;0+1→2+1)
excitation strength in 46Ar for five different minimum impact
parameters. Our findings underline the validity, feasibility, and
perspective of this technique for the study of exotic nuclei also in the
regime of higher beam energy.
Physical Review C 06/2003; 68(1):14302. · 3.31 Impact Factor
-
A Gade,
D Bazin,
C M Campbell,
J A Church,
D C Dinca,
J Enders,
T Glasmacher,
Z Hu,
K W Kemper,
W F Mueller,
H Olliver,
B C Perry, L A Riley,
B T Roeder,
B M Sherrill,
J R Terry
[show abstract]
[hide abstract]
ABSTRACT: Intermediate-energy Coulomb excitation is a key method to investigate collectivity in exotic nuclei far from β stability. We report on the measurement of the absolute B(E2;01+→21+) excitation strength in 46Ar for five different minimum impact parameters. Our findings underline the validity, feasibility, and perspective of this technique for the study of exotic nuclei also in the regime of higher beam energy.
Physical Review C. 01/2003; 68(1):014302 1-4.
-
P D Cottle,
Z Hu,
B V Pritychenko,
J A Church,
M Fauerbach,
T Glasmacher,
R W Ibbotson,
K W Kemper, L A Riley,
H Scheit,
M Steiner
[show abstract]
[hide abstract]
ABSTRACT: We measured the strength of the 0(+)(gs)-->2(+)(1) excitations in the radioactive mirror nuclei 32Ar and 32Si using the techniques of intermediate-energy Coulomb excitation for 32Ar and inelastic proton scattering in inverse kinematics for 32Si. The 32Ar measurement, taken together with previously existing Coulomb excitation data for 32Si, yields the isoscalar and isovector multipole matrix elements for the 0(+)(1)-->2(+)(1) transition between T = 2 states in the A = 32 system. The proton scattering measurement for 32Si, when combined with the Coulomb excitation data for this nucleus, yields a ratio of neutron and proton matrix elements, M(n)/M(p), for 32Si.
Physical Review Letters 05/2002; 88(17):172502. · 7.37 Impact Factor
