Probing new bosons and nuclear structure with ytterbium isotope shifts

In this Letter, we present mass-ratio measurements on highly charged Yb${}^{42+}$ ions with a precision of $4\times {10}^{-12}$ and isotope-shift measurements on Yb${}^{+}$ on the ${}^2$S${}_{1\mathrm{/}2}$ $\to$ ${}^2$D${}_{5\mathrm{/}2}$ and ${}^2$S${}_{1\mathrm{/}2}$ $\to$ ${}^2$F${}_{7\mathrm{/}2}$ transitions with a precision of $4\times {10}^{-9}$ for the isotopes ${}^{168,170,172,174,176}$Yb. We present a new method that allows us to extract higher-order changes in the nuclear charge distribution along the Yb isotope chain, benchmarking ab-initio nuclear structure calculations. Additionally, we perform a King plot analysis to set bounds on a fifth force in the keV$\mathrm{/}{c}^2$ to MeV$\mathrm{/}{c}^2$ range coupling to electrons and neutrons.