Measurement Of Isotope Shifts Of 2-Photon Transitions In Beryllium

We have measured $^{10}\mathrm{Be}$${:}^{9}$Be isotope shifts in the $^{1}\mathrm{S}$ and $^{1}\mathrm{D}$ Rydberg series by resonance-ionization mass spectrometry. Pronounced interference of exchange and correlation contributions to the isotope shift is observed in the $^{1}\mathrm{D}$ series, reflecting strong interaction of 2snd and 2pnp channels. The finite-mass correction to the ionization energy of $^{10}\mathrm{Be}$ is inferred to be 270\ifmmode\pm\else\textpm\fi{}40 MHz.