41 research outputs found
Quadrupole moment of the 6â isomeric state in 66Cu: Interplay between different nuclear deformation driving forces
AbstractWe have measured the spectroscopic quadrupole moment of the 6â isomeric state in 66Cu to be |Qs|=18.6(12) efm2. This state results from a weak coupling of the Ïp3/2 and the Îœg9/2 orbitals, which lead to sizable deformation at oblate and prolate shapes, correspondingly, in the 68Ni region. The interplay between these two different deformation-driving orbitals is observed at N=37 for the 6â state resulting in a most probable oblate shape
Calibration of the ISOLDE acceleration voltage using a high-precision voltage divider and applying collinear fast beam laser spectroscopy
A high-voltage divider with accuracy at the ppm level and collinear laser
spectroscopy were used to calibrate the highvoltage installation at the
radioactive ion beam facility ISOLDE at CERN. The accurate knowledge of this
voltage is particularly important for collinear laser spectroscopy
measurements. Beam velocity measurements using frequencycomb based collinear
laser spectroscopy agree with the new calibration. Applying this, one obtains
consistent results for isotope shifts of stable magnesium isotopes measured
using collinear spectroscopy and laser spectroscopy on laser-cooled ions in a
trap. The long-term stability and the transient behavior during recovery from a
voltage dropout were investigated for the different power supplies currently
applied at ISOLDE.Comment: 13 pages, 6 figure
Unexpected high-energy Îł emission from decaying exotic nuclei
Abstract The N = 52 Ga 83 ÎČ decay was studied at ALTO. The radioactive 83Ga beam was produced through the ISOL photofission technique and collected on a movable tape for the measurement of Îł-ray emission following ÎČ decay. While ÎČ-delayed neutron emission has been measured to be 56â85% of the decay path, in this experiment an unexpected high-energy 5â9 MeV Îł-ray yield of 16(4)% was observed, coming from states several MeVs above the neutron separation threshold. This result is compared with cutting-edge QRPA calculations, which show that when neutrons deeply bound in the core of the nucleus decay into protons via a GamowâTeller transition, they give rise to a dipolar oscillation of nuclear matter in the nucleus. This leads to large electromagnetic transition probabilities which can compete with neutron emission, thus affecting the ÎČ-decay path. This process is enhanced by an excess of neutrons on the nuclear surface and may thus be a common feature for very neutron-rich isotopes, challenging the present understanding of decay properties of exotic nuclei
Perspective on light- and intermediate-mass nuclei from a dedicated laser spectroscopy
International audienc
Instrumentation for high-resolution laser spectroscopy at the ALTO radioactive-beam facility
International audienceCollinear laser spectroscopy is one of the essential tools for nuclear-structure studies. It allows nuclear electromagnetic properties of ground and isomeric states to be extracted with high experimental precision. Radioactive-beam facilities worldwide strive to introduce such capabilities or to improve existing ones. Here we present the implementation of collinear laser spectroscopy at the ALTO research laboratory, along with data from successful off-line commissioning using sodium beam. The instrumental constituents are discussed with emphasis on simple technical solutions and maximized use of standard equipment. Potential future applications are outlined
Magnetism of an Excited Self-Conjugate Nucleus: Precise Measurement of the g Factor of the 2(1)(+) State in Mg-24
International audienceA precise measurement of the g factor of the first-excited state in the self-conjugate (N = Z) nucleus Mg-24 is performed by a new time-differential recoil-in-vacuum method based on the hyperfine field of hydrogenlike ions. Theory predicts that the g factors of such states, in which protons and neutrons occupy the same orbits, should depart from 0.5 by a few percent due to configuration mixing and meson-exchange effects. The experimental result, g = 0.538 +/- 0.013, is in excellent agreement with recent shell-model calculations and shows a departure from 0.5 by almost 3 standard deviations, thus achieving, for the first time, the precision and accuracy needed to test theory. Proof of the new method opens the way for wide applications including measurements of the magnetism of excited states of exotic nuclei produced as radioactive beams
Evidence for Increased neutron and proton excitations between 51-63Mn
The hyperfine structures of the odd-even 51â63Mn atoms (N = 26 â 38) were measured using bunched
beam collinear laser spectroscopy at ISOLDE, CERN. The extracted spins and magnetic dipole moments
have been compared to large-scale shell-model calculations using different model spaces and effective
interactions. In the case of 61,63Mn, the results show the increasing importance of neutron excitations
across the N = 40 subshell closure, and of proton excitations across the Z = 28 shell gap. These
measurements provide the first direct proof that proton and neutron excitations across shell gaps are
playing an important role in the ground state wave functions of the neutron-rich Mn isotopes.peerReviewe