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C Fransen,
A Dewald,
T Baumann,
D Bazin,
A Blazhev,
B A Brown, A Chester,
A Gade,
T Glasmacher,
P T Greenlees, [......],
W Rother,
P Ruotsalainen,
J Saren,
C Scholey,
J Sorri,
K Starosta,
A Stolz,
J Uusitalo,
P Voss,
D Weisshaar
[show abstract]
[hide abstract]
ABSTRACT: Absolute transition probabilities are fundamental observables for nuclear structure. The recoil-distance-Doppler-shift (RDDS) technique, also called plunger technique, is a well established tool for the determination of these important experimental quantities via the measurement of lifetimes of excited nuclear states. Nowadays nuclear structure investigations are concentrated on exotic nuclei which are often produced with extremely small cross sections or with very low beam intensities. In order to use the RDDS technique also for the investigation of very exotic nuclei this method has to be adapted to the specific needs of these special reactions. This article gives an overview on recent RDDS measurements with the new differential plunger in combination with particle detectors and recoil spectrometers. These were done with projectile multistep Coulomb excitation at low beam energies (≈ 5 MeV/u) and at intermediate beam energies (≈ 100 MeV/u) using one step Coulomb excitations and knockout reactions.
Journal of Physics Conference Series 02/2010; 205(1):012043.
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A. Dewald,
K. Starosta,
P. Petkov,
M. Hackstein,
W. Rother,
P. Adrich,
A. M. Amthor,
T. Baumann,
D. Bazin,
M. Bowen, [......],
D. Miller,
V. Moeller,
R. P. Norris,
T. Pissulla,
M. Portillo,
Y. Shimbara,
A. Stolz,
C. Vaman,
P. Voss,
D. Weisshaar
[show abstract]
[hide abstract]
ABSTRACT: Absolute transition probabilities of the first 2+ state in 110,114Pd were remeasured using the recoil distance Doppler shift technique following projectile Coulomb excitation at intermediate beam energies for the first time. The 110Pd experiment served to check the novel technique as well as the method used for the data analysis which is based on the examination of γ‐ray lineshapes. Whereas the measured B(E2) value for 110Pd agrees very well with the literature, the value obtained for 114Pd differs considerably. The data is also used to test a novel concept, called the valence proton symmetry, which allows one to extrapolate nuclear properties to very neutron rich nuclei.
AIP Conference Proceedings. 01/2009; 1090(1):135-139.
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C Vaman,
C Andreoiu,
D Bazin,
A Becerril,
B A Brown,
C M Campbell, A Chester,
J M Cook,
D C Dinca,
A Gade, [......],
D Miller,
V Moeller,
W F Mueller,
A Schiller,
K Starosta,
A Stolz,
J R Terry,
A Volya,
V Zelevinsky,
H Zwahlen
[show abstract]
[hide abstract]
ABSTRACT: Rare isotope beams of neutron-deficient 106,108,110Sn from the fragmentation of 124Xe were employed in an intermediate-energy Coulomb excitation experiment. The measured B(E2,0(1)(+)-->2(1)(+)) values for 108Sn and 110Sn and the results obtained for the 106Sn show that the transition strengths for these nuclei are larger than predicted by current state-of-the-art shell-model calculations. This discrepancy might be explained by contributions of the protons from within the Z = 50 shell to the structure of low-energy excited states in this region.
Physical Review Letters 10/2007; 99(16):162501. · 7.37 Impact Factor
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C. Vaman,
C. Andreoiu,
D. Bazin,
A. Becerril,
B. A. Brown,
C. M. Campbell, A. Chester,
J. M. Cook,
D. C. Dinca,
A. Gade, [......],
D. Miller,
V. Moeller,
W. F. Mueller,
A. Schiller,
K. Starosta,
A. Stolz,
J. R. Terry,
A. Volya,
V. Zelevinsky,
H. Zwahlen
[show abstract]
[hide abstract]
ABSTRACT: Rare isotope beams of neutron-deficient Sn106,108,110 from the
fragmentation of Xe124 were employed in an intermediate-energy Coulomb
excitation experiment. The measured
B(E2,01+→21+) values
for Sn108 and Sn110 and the results obtained for the Sn106 show that the
transition strengths for these nuclei are larger than predicted by
current state-of-the-art shell-model calculations. This discrepancy
might be explained by contributions of the protons from within the Z=50
shell to the structure of low-energy excited states in this region.
Physical Review Letters 09/2007; 99(16):162501. · 7.37 Impact Factor
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K Starosta,
A Dewald,
A Dunomes,
P Adrich,
A M Amthor,
T Baumann,
D Bazin,
M Bowen,
B A Brown, A Chester, [......],
R P Norris,
T Pissulla,
M Portillo,
W Rother,
Y Shimbara,
A Stolz,
C Vaman,
P Voss,
D Weisshaar,
V Zelevinsky
[show abstract]
[hide abstract]
ABSTRACT: Transition rate measurements are reported for the 2(1)+ and 2(2)+ states in N=Z 64Ge. The experimental results are in excellent agreement with large-scale shell-model calculations applying the recently developed GXPF1A interactions. The measurement was done using the recoil distance method (RDM) and a unique combination of state-of-the-art instruments at the National Superconducting Cyclotron Laboratory (NSCL). States of interest were populated via an intermediate-energy single-neutron knockout reaction. RDM studies of knockout and fragmentation reaction products hold the promise of reaching far from stability and providing lifetime information for excited states in a wide range of nuclei.
Physical Review Letters 08/2007; 99(4):042503. · 7.37 Impact Factor
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K. Starosta,
A. Dewald,
A. Dunomes,
P Adrich,
A. M. Amthor,
T. Baumann,
D. Bazin,
M. Bowen,
B A Brown, A. Chester, [......],
R. P. Norris,
T. Pissulla,
M. Portillo,
W. Rother,
Y. Shimbara,
A. Stolz,
C. Vaman,
P Voss,
D. Weisshaar,
V. Zelevinsky
[show abstract]
[hide abstract]
ABSTRACT: Transition rate measurements are reported for the first and the second 2+ states in N=Z 64Ge. The experimental results are in excellent agreement with large-scale Shell Model calculations applying the recently developed GXPF1A interactions. Theoretical analysis suggests that 64Ge is a collective gamma-soft anharmonic vibrator. The measurement was done using the Recoil Distance Method (RDM) and a unique combination of state-of-the-art instruments at the National Superconducting Cyclotron Laboratory (NSCL). States of interest were populated via an intermediate-energy single-neutron knock-out reaction. RDM studies of knock-out and fragmentation reaction products hold the promise of reaching far from stability and providing lifetime information for excited states in a wide range of nuclei.
04/2007;
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C. Vaman,
C. Andreoiu,
D. Bazin,
A. Becerril,
A Brown,
C M Campbell, A. Chester,
J M Cook,
D C Dinca,
A Gade, [......],
D Miller,
V. Moeller,
W. F. Mueller,
A. Schiller,
K. Starosta,
A. Stolz,
J R Terry,
A. Volya,
V. Zelevinsky,
H. Zwahlen
[show abstract]
[hide abstract]
ABSTRACT: Rare isotope beams of neutron-deficient $^{106,108,110}$Sn nuclei from the fragmentation of $^{124}$Xe were employed in an intermediate-energy Coulomb excitation experiment yielding $B(E2, 0^+_1 \to 2^+_1)$ transition strengths. The results indicate that these $B(E2,0^+_1 \to 2^+_1)$ values are much larger than predicted by current state-of-the-art shell model calculations. This discrepancy can be explained if protons from within the Z = 50 shell are contributing to the structure of low-energy excited states in this region. Such contributions imply a breaking of the doubly-magic $^{100}$Sn core in the light Sn isotopes.
01/2007;
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[show abstract]
[hide abstract]
ABSTRACT: Parity is a key observable in nuclear spectroscopy. Linear polarization measurements of $\gamma$-rays are a probe to access the parities of energy levels. Utilizing the segmentation of detectors in the Segmented Germanium Array (SeGA) at the NSCL and analyzing the positions of interaction therein allows the detectors to be used as Compton polarimeters. Unlike other segmented detectors, SeGA detectors are irradiated from the side to utilize the transversal segmentation for better Doppler corrections. Sensitivity in such an orientation has previously been untested. A linear polarization sensitivity $Q \approx 0.14$ has been measured in the 350-keV energy range for SeGA detectors using $\alpha$-$\gamma$ correlations from a \nuc{249}{Cf} source. Comment: 7 pages, 9 figures
12/2006;
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A. Chester,
P Adrich,
A. Becerril,
D. Bazin,
C M Campbell,
J M Cook,
D C Dinca,
W. F. Mueller,
D Miller,
V. Moeller,
R. P. Norris,
M. Portillo,
K. Starosta,
A. Stolz,
J R Terry,
H. Zwahlen,
C. Vaman,
A. Dewald
[show abstract]
[hide abstract]
ABSTRACT: A novel method for picosecond lifetime measurements of excited gamma-ray emitting nuclear states has been developed for fast beams from fragmentation reactions. A test measurement was carried out with a beam of 124Xe at an energy of ~55 MeV/u. The beam ions were Coulomb excited to the first 2+ state on a movable target. Excited nuclei emerged from the target and decayed in flight after a distance related to the lifetime. A stationary degrader positioned downstream with respect to the target was used to further reduce the velocity of the excited nuclei. As a consequence, the gamma-ray decays from the 2+ excited state that occurred before or after traversing the degrader were measured at a different Doppler shift. The gamma-ray spectra were analyzed from the forward ring of the Segmented Germanium Array; this ring positioned at 37 deg. simultaneously provides the largest sensitivity to changes in velocity and the best energy resolution. The ratio of intensities in the peaks at different Doppler shifts gives information about the lifetime if the velocity is measured. The results and range of the application of the method are discussed. Comment: 24 pages, 10 figures
12/2005;
