Principal Investigators:

• D. Budker (Helmholtz Institute Mainz; PRISMA+ Cluster of Excellence;
  Institute for Physics - QUANTUM group, Matter - Antimatter Asymmetry, JGU Mainz)
• Ch. E. Düllmann (Helmholtz Institute Mainz; PRISMA+ Cluster of Excellence;
  Department Chemistry - TRIGA Site, Superheavy Element Chemistry, JGU Mainz;
  GSI Helmholtzzentrum für Schwerionenforschung Darmstadt)
• F. Schmidt-Kaler (Helmholtz Institute Mainz; PRISMA+ Cluster of Excellence;
  Institute for Physics - QUANTUM group, Quantenbit AG, JGU Mainz)
• L. von der Wense (Institute for Physics - QUANTUM group, NuQuant, JGU Mainz)

Research:

TACTICa uses atomic physics methods to investigate thorium isotopes including the metastable low energy nuclear state in ^229mTh. The optical ground state transition of isomeric ²²⁹Th is the only nuclear transition that potentially can be interrogated using lasers. Controlling this transition opens an interesting window into high-precision tests of the standard model and on possible variation of fundamental constants.
Thus TACTICa aims to deploy ion trapping techniques like quantum logic spectroscopy to gain access to the nuclear structure of thorium.

TACTICa aims for combining unique expertise of nuclear chemistry, experimental quantum science, theoretical physics from Budker group, and quantum chemistry from Gaul group.

This way, we will first vastly improve the accuracy of spectroscopic investigations of the nuclear Th isotopes including the isomer in ²²⁹Th, and eventually realize quantum logic spectroscopy and quantum-enhanced measurements on thorium for fundamental research.

Ion trap:

TACTICa uses state of the art ion trapping techniques to test the standard model of physics with highest precision and respect to precise determination of the nuclear moments, hyperfine intervals, and isotopic and isomeric shifts of thorium ions. Thorium ions are trapped and sympathetically cooled inside of a calcium ion crystal in a Paul trap designed and developed in the Quantenbit AG.

Th ion sources:

TACTICa follows two different approaches for Th ion production: 1. Laser ablation of macroscopically samples of thorium and 2. Alpha decay of uranium mother nuclides. Therfore, a laser ablation setup and a newly built buffer gas stopping cell, built in the NuQuant Lab, is being used to implement Th ions into Ca ion crystals. For further information visit Sources of TACTICa.

Results:

As an important first demonstration, in 2018, single ²³²Th⁺ ions were trapped together with Ca⁺ ions forming a so-called “Wigner crystal”, sympathetically cooled and characterized.

We demonstrate the laser-fluence-dependent production of thorium molecular ions in different charge states. Using laser ablation of microgram thorium fluoride crystals, species such as ThF²⁺ and ThF³⁺ are efficiently produced. These múltiply-charged ions are ideal candidates for fundamentel symmetry tests.

The TACTICa collaboration is joined by the NuQuant project led by Lars von der Wense. NuQuant aims to realize laser spectroscopy of the thorium-229 nucleus. With the development of a continuous-wave laser at 150 nm, the project seeks to achieve coherent control of the nuclear excited state, paving the way toward a nuclear optical clock and future applications in nuclear quantum optics.