Wigner Crystals of 229Th for Optical Excitation of the Nuclear Isomer

TL;DR

This paper reports the creation of laser-cooled Wigner crystals of 229Th3+ ions, measurements of hyperfine constants and isotope shifts, and deduces a nuclear quadrupole moment, advancing the goal of optical excitation of the 229Th nuclear isomer.

Contribution

It introduces the formation of Wigner crystals of 229Th3+ ions and provides new hyperfine and isotope shift data crucial for nuclear excitation studies.

Findings

Measured hyperfine constants for four electronic levels.

Determined isotope shifts for three optical transitions.

Deduced nuclear electric quadrupole moment Q = 3.11(16) eb.

Abstract

We have produced laser-cooled Wigner crystals of 229Th3+ in a linear Paul trap. The magnetic dipole (A) and electric quadrupole (B) hyperfine constants for four low-lying electronic levels and the relative isotope shifts with respect to 232Th3+ for three low-lying optical transitions are measured. Using the hyperfine B constants in conjunction with prior atomic structure calculations, a new value of the spectroscopic nuclear electric quadrupole moment Q = 3.11(16) eb is deduced. These results are a step towards optical excitation of the low-lying isomer level in the 229Th nucleus.