Fig. 1: Overview of the experimental results.
Top: ion rate obtained during the laser scan of 78Cu as a function of resonant laser frequency relative to the hyperfine structure centroid. Error bars show the statistical uncertainty (one standard deviation). The solid line shows the best-fitting set of Voigt profiles centred at the resonance locations (see Methods). Bottom: values of \(\delta \left\langle {r}^{2}\right\rangle\) for 63−66,68−78Cu (relative to 65Cu) from this work as a function of neutron number N, alongside the literature values for 58−62,67Cu (ref. 9). The inset shows the OES of the radii defined by equation (1). Error bars are statistical (one standard deviation). In the main plot, these errors are too small to be seen except for 78Cu. The blue shaded area represents the systematic uncertainty due to the atomic parameters.
