T. E. Cocolios

Studies of pear-shaped nuclei using accelerated radioactive beams

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 were performed using accelerated beams of heavy, radioactive ions. Our data on 220Rn and 224Ra show clear evidence for stronger octupole deformation in the latter. The results enable discrimination between differing theoretical approaches to octupole correlations, and help to constrain suitable candidates for experimental studies of atomic electric-dipole moments that might reveal extensions to the standard model.

Early onset of ground state deformation in neutron deficient polonium isotopes

In-source resonant ionization laser spectroscopy of the even-A polonium isotopes (192-210,216,218)Po has been performed using the 6p(3)7s (5)S(2) to 6p(3)7p (5)P(2) (λ=843.38u2009u2009nm) transition in the polonium atom (Po-I) at the CERN ISOLDE facility. The comparison of the measured isotope shifts in (200-210)Po with a previous data set allows us to test for the first time recent large-scale atomic calculations that are essential to extract the changes in the mean-square charge radius of the atomic nucleus. When going to lighter masses, a surprisingly large and early departure from sphericity is observed, which is only partly reproduced by beyond mean field calculations.

Early onset of deformation in the neutron-deficient polonium isotopes

In-source laser spectroscopy has been performed at CERN-ISOLDE with the RILIS laser ion source on 191–204,206,208–211,216,218Po. New information on the β decay of 199Po were extracted in the process, challenging previous results. Large-scale atomic calculations were performed to extract the changes in the mean-square charge radius δr2 from the isotope shifts. The δr2 for the even-A isotopes reveal a large deviation from the spherical droplet model for N < 116.

Detailed α-decay study of 180Tl

A detailed

Structure of Pb-191 from alpha- and beta-decay spectroscopy

alpha

New Type of Asymmetric Fission in Proton-Rich Nuclei

-decay spectroscopy study of

The Miniball spectrometer

^{180}mathrm{Tl}

New developments of the in-source spectroscopy method at RILIS/ISOLDE

has been performed at ISOLDE (CERN).

In-source laser spectroscopy with the Laser Ion Source and Trap: first direct study of the ground-state properties of 217,219Po

Z

Evolution of fission-fragment mass distributions in the neutron-deficient lead region

-selective ionization by the Resonance Ionization Laser Ion Source (RILIS) coupled to mass separation provided a high-purity beam of