Speaker
Description
In the search for $\mathcal{P,T}$-odd effects, polar molecules can exhibit orders of magnitude larger enhancements than atoms [1,2] due to large internal fields. Choosing molecules, however, imposes additional challenges, such as the need of molecular instead of atomic theory or an analysis of congested rovibronic spectra. The initial difficulty is the search for suitable systems with large enhancements of $\mathcal{P,T}$-odd properties, that are easy to produce, simple to handle and, preferably, contain optical cycling centers for laser-cooling. Highly-charged actinide molecules like PaF$^{3+}$ [3] are predicted to fullfill these criteria.
Ions have the experimental advantage that they can be guided by electric fields and sympathetically cooled [4] with long trapping times which might open up a pathway for subsequent direct laser-cooling of well chosen systems. With increasing charge, relativistic effects become more dominant, which increases the $\mathcal{P,T}$-violating enhancement factors and the electronic spectra become typically compressed, which is favourable for the search for variation of fundamental constans.
In this contribution we will discuss trends in the enhancement of various properties relevant for tests of fundamental physics of simple diatomic, molecular ions with the focus on molecules with a doublet ground state. The properties are computed using the quasi-relativistic toolbox approach outlined in [5].
[1] D. DeMille, Physics Today (2015), 68, 34.
[2] V. Andreev et al., Nature (2018), 562, 355.
[3] C. Zülch, K. Gaul, S. M. Giesen, R. F. G. Ruiz, R. Berger, arXiv (2022), 2203.10333.
[4] W. B. Cairncross et al., Phys. Rev. Lett. (2017), 119, 153001.
[5] K. Gaul and R. Berger, J. Chem. Phys. (2020), 152, 044101.
