Isotope shift in the electron affinity of chlorine.

The specific mass shift in the electron affinity between 35Cl and 37Cl has been determined by tunable laser photodetachment spectroscopy to be −0.51(14) GHz. The isotope shift was observed as a difference in the onset of the photodetachment process for the two isotopes. In addition, the electron affinity of Cl was found to be 29 138.59(22) cm−1, giving a factor of 2 improvement in the accuracy over earlier measurements. Many-body calculations including lowest-order correlation effects demonstrates the sensitivity of the specific mass shift and show that the inclusion of higherorder correlation effects would be necessary for a quantitative description.