There is a large body of evidence that atomic nuclei can undergo octupole distortion and assume the shape of a pear. This phenomenon is important for measurements of electric-dipole moments of atoms, ...which would indicate CP violation and hence probe physics beyond the Standard Model of particle physics. Isotopes of both radon and radium have been identified as candidates for such measurements. Here, we observed the low-lying quantum states in
Rn and
Rn by accelerating beams of these radioactive nuclei. We show that radon isotopes undergo octupole vibrations but do not possess static pear-shapes in their ground states. We conclude that radon atoms provide less favourable conditions for the enhancement of a measurable atomic electric-dipole moment.
Coulomb excitation of Rn 222 Spagnoletti, P.; Butler, P. A.; Gaffney, L. P. ...
Physical review. C,
02/2022, Letnik:
105, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The nature of quadrupole and octupole collectivity in 222Rn was investigated by determining the electric-quadrupole (E2) and octupole (E3) matrix elements using subbarrier, multistep Coulomb ...excitation. The radioactive 222Rn beam, accelerated to 4.23 MeV/u, was provided by the HIE-ISOLDE facility at CERN. Data were collected in the Miniball γ-ray spectrometer following the bombardment of two targets, 120Sn and 60Ni. Transition E2 matrix elements within the ground-state and octupole bands were measured up to 10ℏ and the results were consistent with a constant intrinsic electric-quadrupole moment, 518(11)efm2. The values of the intrinsic electric-octupole moment for the 0+→3− and 2+→5− transitions were found to be respectively 2360+300−210efm3 and 2300+300−500efm3 while a smaller value, 1200+500−900efm3, was found for the 2+→1− transition. In addition, four excited non-yrast states were identified in this work via γ−γ coincidences.
A novel Monte Carlo technique has been developed to determine lifetimes of excited states in the tens-to-hundreds femtoseconds range in products of low-energy heavy-ion binary reactions, with complex ...velocity distributions. The method is based on a detailed study of Doppler-broadened
γ
-ray lineshapes. Its relevance is demonstrated in connection with the
18
O
(
7.0
MeV/u
)
+
181
Ta
experiment, performed at GANIL with the AGATA+VAMOS+PARIS setup, to study neutron-rich O, C, N, ... nuclei. Excited states in
17
O
and
19
O
, with known lifetimes, are used to validate the method over the
∼
20
-
400
fs
lifetime-sensitivity range. Emphasis is given to the unprecedented position resolution provided by
γ
-tracking arrays, which turns out to be essential for reaching the required accuracy in Doppler-shift correction. The technique is anticipated to be an important tool for lifetime investigations in exotic neutron-rich nuclei, produced with intense ISOL-type beams.
There is sparse direct experimental evidence that atomic nuclei can exhibit stable "pear" shapes arising from strong octupole correlations. In order to investigate the nature of octupole collectivity ...in radium isotopes, electric octupole (E3) matrix elements have been determined for transitions in ^{222,228}Ra nuclei using the method of sub-barrier, multistep Coulomb excitation. Beams of the radioactive radium isotopes were provided by the HIE-ISOLDE facility at CERN. The observed pattern of E3 matrix elements for different nuclear transitions is explained by describing ^{222}Ra as pear shaped with stable octupole deformation, while ^{228}Ra behaves like an octupole vibrator.
Lifetime measurement of excited states in 46Ti Goldkuhle, A.; Fransen, C.; Dewald, A. ...
The European physical journal. A, Hadrons and nuclei,
2019/4, Letnik:
55, Številka:
4
Journal Article
Recenzirano
.
The level lifetimes of the yrast 2
1
+
, 4
1
+
and 6
1
+
states and an upper limit of the lifetime of the 8
1
+
state in
46
Ti have been measured with high accuracy exploiting the recoil distance ...Doppler-shift method (RDDS) and using
γ
γ
coincidences. The nuclei were populated by the fusion evaporation reaction
40
Ca(
9
Be, 2p1n)
46
Ti at a beam energy of
E
=
33
MeV at the FN tandem accelerator of the University of Cologne, Germany. Lifetimes were extracted using the established differential decay curve method (DDCM).
In this study we present the preliminary results about the lifetimes of the 2 2 + , 4 1 + states of 208Po and the upper limit of the lifetime of the 2 1 + state. For measuring the lifetimes of the 2 ...1 + and 4 1 + states the Recoil Distance Doppler Shift (RDDS) method and for the lifetime of the 2 2 + state the Doppler Shift Attenuation method (DSAM) were used. The resulting absolute transition strength B ( M 1 ; 2 2 + → 2 1 + ) ≥ 0.122 ( 20 ) μ N 2 reveals the predominant isovector nature of the 2 2 + state of 208Po.
The lifetimes of the first 2+ excited states of 212,210Po were measured in two transfer reactions 208Pb(12C,8Be)212Po and 208Pb(12C,10Be)210Po by the Recoil Distance Doppler Shift (RDDS) method and ...by the Doppler Shift Attenuation method (DSAM), respectively. The derived absolute B(E2) values of 2.6(3) W.u. for 212Po and 1.83(28) W.u. for 210Po indicate low collectivity. It is shown that the properties of the yrast 21+, 41+, 61+ and 81+ states in both nuclei cannot be described consistently in the framework of nuclear shell models. It is also demonstrated in the case of 210Po that Quasi-particle Phonon Model (QPM) calculations cannot overcome this problem thus indicating the existence of a peculiarity which is neglected in both theoretical approaches.
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