Laser Probing of Neutron-Rich Nuclei in Light Atoms

TL;DR

This paper combines advanced laser spectroscopy and atomic theory to measure nuclear charge radii of neutron-rich helium, lithium, and beryllium isotopes, providing new insights into nuclear structure without relying on models.

Contribution

It presents the first model-independent determination of charge radii for light halo nuclei using laser spectroscopy and atomic theory advancements.

Findings

Charge radii of 6He and 8He measured independently of nuclear models.

Atomic isotope shifts agree with theoretical calculations.

Results inform nuclear force understanding in neutron-rich environments.

Abstract

The neutron-rich 6He and 8He isotopes exhibit an exotic nuclear structure that consists of a tightly bound 4He-like core with additional neutrons orbiting at a relatively large distance, forming a halo. Recent experimental efforts have succeeded in laser trapping and cooling these short-lived, rare helium atoms, and have measured the atomic isotope shifts along the 4He-6He-8He chain by performing laser spectroscopy on individual trapped atoms. Meanwhile, the few-electron atomic structure theory, including relativistic and QED corrections, has reached a comparable degree of accuracy in the calculation of the isotope shifts. In parallel efforts, also by measuring atomic isotope shifts, the nuclear charge radii of lithium and beryllium isotopes have been studied. The techniques employed were resonance ionization spectroscopy on neutral, thermal lithium atoms and collinear laser spectroscopy on beryllium ions. Combining advances in both atomic theory and laser spectroscopy, the charge radii of these light halo nuclei have now been determined for the first time independent of nuclear structure models. The results are compared with the values predicted by a number of nuclear structure calculations, and are used to guide our understanding of the nuclear forces in the extremely neutron-rich environment.