Laser assisted nuclear decay spectroscopy: A new method for studying neutron-deficient francium

Abstract

Radioactive decay studies of rare isotopes produced at radioactive ion beam facilities have often been hindered by the presence of isobaric and isomeric contamination. The Collinear Resonance Ionization Spectroscopy (CRIS) experiment at ISOLDE, CERN uses laser radiation to stepwise excite and ionize an atomic beam in a particular isomeric state. Detection of this selectively ionized beam of exotic nuclei, from the remaining neutral contaminants, allows ultra-sensitive detection of rare isotopes and nuclear structure measurements in background-free conditions.This thesis outlines the work undertaken in the development of the novel technique of laser assisted nuclear decay spectroscopy. The isomeric ion beam is selected using an atomic resonance of its hyperfine structure, where it is detected to a decay spectroscopy station. This consists of a rotating wheel implantation system for alpha-decay spectroscopy, and up to three germanium detectors around the implantation site for gamma-ray detection.Laser spectroscopy provides a measurement of the spin, moments and change in mean-square charge radii of the ground and isomeric states in the parent nucleus. Complementary information on the level structure of the daughter nucleus comes from the decay spectroscopy, providing further information on the isotope under investigation.The new techniques of collinear resonance ionization spectroscopy and laser assisted nuclear decay spectroscopy have been developed and optimized in the experimental campaign studying the neutron-deficient francium isotopes. In this thesis, the hyperfine structure studies of 202-207,211Fr are presented, alongside the radioactive decay studies of 202,204,218Fr and their isomers.

Date of Award	31 Dec 2013
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Kieran Flanagan (Supervisor)