Grant: Subatomic Physics Envelope - Project

Radioactive molecules, in which one or more of its constituting atoms contain a short-lived radioactive nucleus, have recently been introduced as fascinating objects in fundamental physics research. These radioactive atoms are opening up an additional degree of freedom to synthesise molecular systems which can be tailored to maximise the sensitivity to new physics beyond the standard model of particle physics. For instance, radioactive molecules are intriguing probes for molecular electric dipole moments (EDMs) with unprecedented sensitivity to nuclear time--reversal--breaking Schiff moments. Due to the link between time--reversal breaking and the violation of the combined symmetry of charge conjugation and parity (CP), the discovery of new sources of time--reversal violation could resolve one of the most tantalising puzzles in contemporary physics, i.e. the matter--antimatter asymmetry in the universe. However, radioactive molecules are challenging to address experimentally. In addition to the short half-lives, radioactive samples are only available in minute quantities at dedicated radioactive ion beam facilities such as at the Isotope Separator and Accelerator (ISAC) and Advanced Rare Isotope Laboratory (ARIEL) at TRIUMF, Vancouver. The goal of the present proposal is to pursue the foundational work on selected radioactive molecules which are predicted to exhibit extraordinary enhancements in searches for new physics. First, we will measure the s--wave scattering length between francium atoms. This is the first critical step in order to assembly the ultracold molecule 223FrAg from laser-cooled francium and silver atoms. Second, we will build and operate a cryogenic, buffer-gas-filled ion trap in order to perform spectroscopy of (ionic) radioactive molecules. In particular,  AcF+ promises large EDM enhancements when it incorporates the octupole-deformed Actinium isotopes 223Ac and 225Ac.  In addition to its use for molecular spectroscopy, the device can at a later stage be exploited to cool the molecular degrees of freedom in the RaF- anion as a first step towards experiments with ultra-cold and trapped RaF.  This will establish such a cryogenic trap as a critical tool in order to prepare radioactive molecules for future precision studies in search of new physics.