In this talk I will present recent theoretical work that can utilise high-precision optical spectroscopy to search for new physics. One idea is that effects of new physics that are much too small to isolate directly in a spectroscopic experiment, but are isotope-dependent, can present a relatively clean signal in the isotope shift. Of particular use is the ‘King plot’ which allows separation of atomic and nuclear sectors independently of theory. With modern optical spectroscopy techniques we can now envisage measurement of isotope shift at the ∼Hz level, where deviations from the linearity King plot will become apparent. While many effects in the Standard Model will manifest deviations from linearity in King plots, it is possible that in many cases these effects are relatively small or can be largely removed by theory. New physics, such as a weakly-coupled light scalar particle, could then be detected.

Novel clocks using transitions in highly-charged ions and nuclei can provide unique leverage to detecting new physics, including variations in fundamental constants and violations of Lorentz invariance. The variety of highly charged ions available provides new opportunities for experiment. For example, choosing HCIs near level crossings allows optical transitions with high sensitivity to variations of the fine-structure constant, and many opportunities to control systematics. Other ions can provide electronic bridges to the low-lying nuclear transitions in Th-229 and U-235.