Early onset of ground-state deformation in the neutron-deficient polonium isotopes

TL;DR

This study uses laser spectroscopy to measure isotope shifts in polonium isotopes, revealing early nuclear deformation in lighter isotopes, challenging existing theoretical models.

Contribution

First experimental comparison of isotope shifts in polonium isotopes with advanced atomic calculations, highlighting early onset of nuclear deformation.

Findings

Large and early departure from sphericity in lighter polonium isotopes

Partial reproduction of deformation by Beyond Mean Field calculations

Validation of atomic calculations for extracting nuclear charge radii

Abstract

In-source resonant ionization laser spectroscopy of the even-$A$ polonium isotopes $^{192-210,216,218}$Po has been performed using the $6p^37s$ $^5S_2$ to $6p^37p$ $^5P_2$ ($\lambda=843.38$ nm) 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 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.