Laser and decay spectroscopy of the short-lived isotope Fr214 in the vicinity of the N=126 shell closure

Abstract

Combined decay and laser spectroscopy measurements of the isotope 214 Fr are reported, using the collinear resonance ionization spectroscopy (CRIS) technique at the ISOLDE facility at CERN. For the I π = (1 − ) spin assignment, the g-factor value of g( 214 Fr) = +0.241(16) corresponds to a relatively pure (π 1h 9/2 ⊗ ν2g 9/2 ) ground-state configuration. An alternative interpretation with g( 214 Fr) = +0.144(10), for a (2 − ) spin assignment suggests a greater contribution of configuration mixing with the ν1i 11/2 orbital. As the N = 126 shell closure is passed, a kink is observed at the δ r 2 213,214 value, which is analogous to the behavior observed in the neighboring isotopic chains.

Collinear laser spectroscopy at ISOLDE: new methods and highlights

“…The 1.5GHz linewidth laser system has proved an ideal method for rapidly locating resonances, which has been recently demonstrated by the measurement of the hyperfine structure and isotope shift of 214 Fr. With a half-life of 5(1)ms, this is the shortest-lived nuclear ground state to be measured with laser spectroscopy [85,105], where ISOL production is the limiting factor.…”

Charge radii, moments and masses of mercury isotopes across the N = 126 shell closure

“…The kink in the relative mean square charge radii (δ r 2 ) at the N = 126 shell closure has long been considered as a benchmark for testing theoretical calculations. Traditionally the lead isotopic chain was employed [1][2][3][4][5], but new experimental results in this region revealing the systemics of other isotopic chains [6][7][8][9], mass measurements, and odd-even staggering (OES) in charge radii offer the opportunity to broaden this benchmark. The droplet model is unable to reproduce this kink because of the absence of single-particle degrees of freedom [10].…”

Optimising the Collinear Resonance Ionisation Spectroscopy (CRIS) experiment at CERN-ISOLDE

“…These measurements allow nuclear model independent studies of the electromagnetic properties of exotic isotopes, such as the nuclear spin, nuclear magnetic dipole and electric quadrupole moments as well as changes in mean squared charge radii [5]. States with half-lives as short as t 1/2 =5 ms ( 214 Fr) have been measured using this technique [6].…”