Search results for "Coulomb [force]"
showing 10 items of 103 documents
Coulomb excitation of pear-shaped nuclei
2019
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 have observed the low-lying quantum states in 224Rn and 226Rn 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 condition…
Evolution of Octupole Deformation in Radium Nuclei from Coulomb Excitation of Radioactive Ra222 and Ra228 Beams
2020
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.
Development of quadrupole collectivity in the neutron-rich Ni, Zn, Ge, and Se isotopes
2003
An experiment was performed to study the collective properties of neutron-rich Ni, Zn, Ge, and Se isotopes. Of particular interest is the vicinity of the N = 50 and Z = 28 shell closures. For most neutron-rich nuclei in this region of the chart of nuclei the B(E2) values of the transitions from the ground to the first excited 2+ states are unknown. This information would give valuable insight into the changes in nuclear structure when going to more neutron-rich nuclei.
Enhanced Quadrupole and Octupole Strength in Doubly Magic Sn132
2018
The first 2+ and 3- states of the doubly magic nucleus Sn132 are populated via safe Coulomb excitation employing the recently commissioned HIE-ISOLDE accelerator at CERN in conjunction with the highly efficient MINIBALL array. The Sn132 ions are accelerated to an energy of 5.49 MeV/nucleon and impinged on a Pb206 target. Deexciting γ rays from the low-lying excited states of the target and the projectile are recorded in coincidence with scattered particles. The reduced transition strengths are determined for the transitions 0g.s.+→21+, 0g.s.+→31-, and 21+→31- in Sn132. The results on these states provide crucial information on cross-shell configurations which are determined within large-sca…
The REX-ISOLDE project
2002
REX-ISOLDE is a pilot experiment at ISOLDE/CERN to study the structure of neutron-rich nuclei (N=20, N=28) with post-accelerated radioactive ion beams (1). Therefore radioactive ions with charge state 1+, which are delivered by the online mass separator ISOLDE, are accelerated up to 2.2 MeV/u by means of a new concept. The radioactive ions are first accumulated in a Penning trap, then charge breeded to a charge-to-mass ratio of 1/4.5 in an Electron Beam Ion Source (EBIS) and finally accelerated. The LINAC consists of three components, namely a Radio Frequency Quadrupole (RFQ) accelerator, which accelerates the ions from 5 to 300 keV/u, an interdigital H-type structure (IH) with a final ener…
Coulomb Excitation of Neutron-Rich Zn Isotopes: First Observation of the21+State inZn80
2007
Neutron-rich, radioactive Zn isotopes were investigated at the Radioactive Ion Beam facility REX-ISOLDE (CERN) using low-energy Coulomb excitation. The energy of the 2(1)+ state in 78Zn could be firmly established and for the first time the 2+ --> 0(1)+ transition in 80Zn was observed at 1492(1) keV. B(E2,2(1)+ --> 0(1)+) values were extracted for (74,76,78,80)Zn and compared to large scale shell model calculations. With only two protons outside the Z=28 proton core, 80Zn is the lightest N=50 isotone for which spectroscopic information has been obtained to date. Two sets of advanced shell model calculations reproduce the observed B(E2) systematics. The results for N=50 isotones indicate a g…
Coulomb Excitation of (142) Xe
2017
5 pags., 2 figs. -- Open Access funded by Creative Commons Atribution Licence 4.0. -- Presented at the XXXV Mazurian Lakes Conference on Physics, Piaski, Poland, September 3–9, 2017.
Sub-Barrier Coulomb Excitation ofSn110and Its Implications for theSn100Shell Closure
2007
The first excited 2(+) state of the unstable isotope Sn-110 has been studied in safe Coulomb excitation at 2.82 MeV/u using the MINIBALL array at the REX-ISOLDE post accelerator at CERN. This is the first measurement of the reduced transition probability of this state using this method for a neutron deficient Sn isotope. The strength of the approach lies in the excellent peak-to-background ratio that is achieved. The extracted reduced transition probability, B(E2 : 0(+) -> 2(+)) 0.220 +/- 0.022e(2) b(2), strengthens the observation of the evolution of the B(E2) values of neutron deficient Sn isotopes that was observed recently in intermediate-energy Coulomb excitation of Sn-108. It implies …
Shape Coexistence in the Neutron-Deficient Even-EvenHg182−188Isotopes Studied via Coulomb Excitation
2014
Coulomb-excitation experiments to study electromagnetic properties of radioactive even-even Hg isotopes were performed with 2.85 MeV/nucleon mercury beams from REX-ISOLDE. Magnitudes and relative signs of the reduced E2 matrix elements that couple the ground state and low-lying excited states in Hg182-188 were extracted. Information on the deformation of the ground and the first excited 0(+) states was deduced using the quadrupole sum rules approach. Results show that the ground state is slightly deformed and of oblate nature, while a larger deformation for the excited 0(+) state was noted in Hg-182; 184. The results are compared to beyond mean field and interacting-boson based models and i…
Studies of pear-shaped nuclei using accelerated radioactive beams
2013
There is strong circumstantial evidence that certain heavy, unstable atomic nuclei are ‘octupole deformed’, that is, distorted into a pear shape. This contrasts with the more prevalent rugby-ball shape of nuclei with reflection-symmetric, quadrupole deformations. The elusive octupole deformed nuclei are of importance for nuclear structure theory, and also in searches for physics beyond the standard model; any measurable electric-dipole moment (a signature of the latter) is expected to be amplified in such nuclei. Here we determine electric octupole transition strengths (a direct measure of octupole correlations) for short-lived isotopes of radon and radium. Coulomb excitation experiments we…