| 1. |
- Schwerdtfeger, W, et al.
(författare)
-
Shape Coexistence Near Neutron Number N=20 : First Identification of the E0 Decay from the Deformed First Excited J(pi)=0(+) State in Mg-30
- 2009
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 103:1, s. 012501-
-
Tidskriftsartikel (refereegranskat)abstract
- The 1789 keV state in Mg-30 was identified as the first excited 0(+) state via its electric monopole (E0) transition to the ground state. The measured small value of rho(2)(E0,0(2)(+)-> 0(1)(+))=(26.2 +/- 7.5)x10(-3) implies within a two-level model a small mixing of competing configurations with largely different intrinsic quadrupole deformation near the neutron shell closure at N=20. Axially symmetric configuration mixing calculations identify the ground state of Mg-30 to be based on neutron configurations below the N=20 shell closure, while the excited 0(+) state mainly consists of two neutrons excited into the nu 1f(7/2) orbital. The experimental result represents the first case where an E0 back decay from a strongly deformed second to the normal deformed first nuclear potential minimum well has been unambiguously identified, thus directly proving shape coexistence at the borderline of the much-debated "island of inversion."
|
|
| 2. |
- Boutami, R., et al.
(författare)
-
Nuclear structure of Ac-231
- 2008
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 811:3-4, s. 244-275
-
Tidskriftsartikel (refereegranskat)abstract
- The low-energy structure of Ac-231 has been investigated by means of gamma ray spectroscopy following the beta(-) decay of Ra-231. Multipolarities of 28 transitions have been established by measuring conversion electrons with a MINI-ORANGE electron spectrometer. The decay scheme of Ra-231 -> Ac-231 has been constructed for the first time. The Advanced Time Delayed beta gamma gamma(t) method has been used to measure the half-lives of five levels. The moderately fast B(EI) transition rates derived suggest that the octupole effects., albeit weak, are still present in this exotic nucleus.
|
|
| 3. |
- Ruchowska, E., et al.
(författare)
-
Nuclear structure of Th-229
- 2006
-
Ingår i: Physical Review C. Nuclear Physics. - : American Physical Society. - 0556-2813 .- 1089-490X. ; 73:4
-
Tidskriftsartikel (refereegranskat)abstract
- Lifetimes of excited states in Th-229, populated in the beta decay of Ac-229, have been measured using the advanced time-delayed beta gamma gamma(t) method. Half-lives of 14 states have been determined including 11 of them for the first time. Twenty-seven new gamma lines have been introduced into the beta-decay scheme of Ac-229 based on results of gamma gamma coincidence measurements. Reduced transition probabilities have been determined for more than 70 gamma transitions in Th-229. Average parallel to D-0 parallel to values of 0.029(1), 0.077(3), and 0.024(5) e fm have been deduced for the lowest K-pi=1/2(+/-),3/2(+/-), and 5/2(+/-) parity partner bands, respectively. Excited states in Th-229 and experimental transition rates have been interpreted within the quasiparticle-plus-phonon model. The half-life of the 3.5-eV, 3/2(+) isomeric state is predicted to be about 10 h. Potential energy surfaces on the (beta(2),beta(3)) plane for the lowest single quasiparticle configurations in Th-229 have been calculated using the Strutinsky method.
|
|
| 4. |
|
|
| 5. |
- Mach, Henryk, et al.
(författare)
-
The single-particle and collective features in the nuclei just above Sn-132
- 2007
-
Ingår i: Acta Physica Polonica B. - 0587-4254 .- 1509-5770. ; 38:4, s. 1213-1218
-
Tidskriftsartikel (refereegranskat)abstract
- The Advanced Time Delayed method has been used to measure the lifetimes of excited states in the exotic nuclei Sb-134, Sb-135 and Te-136 populated in the beta decay of Sn-134, Sn-135 and Sn-136, respectively. High purity Sn beams were extracted at the ISOLDE separator using a novel production technique utilizing the molecular SnS+ beams to isolate Sn from contaminating other fission products. Among the new results we have identified the 1/2(+) state in Sb-135 and its E2 transition to the lower-lying 5/2(+) state was found to be surprisingly collective. This measurement represents also one of the first applications of the LaBr3 scintillator to ultra fast timing.
|
|
| 6. |
- Mach, H., et al.
(författare)
-
New structure information on Mg-30, Mg-31 and Mg-32
- 2005
-
Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-601X .- 1434-6001. ; 25, s. 105-109
-
Konferensbidrag (refereegranskat)abstract
- The fast timing beta gamma gamma(t) method was applied to investigate the level lifetimes in Mg-30,Mg-31,Mg-32. Levels in Mg have been populated in beta and beta-delayed neutron emission of Na, at the ISOLDE facility. From the gamma gamma coincidences a number of new states have been identified and new level schemes were constructed for 30 31,32 Mg. The following preliminary half lives have been determined: T-1/2 = 3.9(4) ns for the 1789 keV state in Mg-30, T-1/2 = 133(8) ps and 10.5(8) us for the 221 keV and 461 keV states in Mg-31, respectively, and T1/2 = 16(4) ps for the 885 keV level in 32Mg. The 1789 keV level was established as a candidate for the intruder 0(+) configuration in Mg-30 with a possible strong E0 branch to the ground state.
|
|
| 7. |
- Mach, Henryk, et al.
(författare)
-
Structure of heavy Fe nuclei at the point of transition at N simular to 37
- 2009
-
Ingår i: Acta Physica Polonica B. - 0587-4254 .- 1509-5770. ; 40:3, s. 477-480
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied energy levels in Fe-63 populated in the beta-decay of Mn-63. A new (preliminary) level scheme of Fe-63 includes 10 excited states connected by 21 gamma-rays. The first excited states at 357 and 451 keV have the level half-lives of 110 ps and 780 ps, respectively. Three states, at 357, 451, and 1132 keV, are strongly beta-fed with log ft similar to 5, while there is only a very week beta-feeding, if any at all, to the ground state. The new results imply that Fe-63 departs from a simple shell model structure observed for heavier N = 37 isotones of Ni-65 and Zn-67.
|
|
| 8. |
|
|
