ris4: A program for relativistic isotope shift calculations

Spectral lines from different isotopes display a small separation in energy, commonly referred to as the line isotope shift. The program RIS 4 (Relativistic Isotope Shift) calculates normal and specific mass shift parameters as well as field shift electronic factors from relativistic multiconfiguration Dirac-Hartree–Fock wave functions. These quantities, together with available nuclear data, determine isotope-dependent energy shifts. Using a reformulation of the field shift, it is possible to study, in a model-independent way, the atomic energy shifts arising from changes in nuclear charge distributions, e.g. deformations. The previous version of this program (ADEK_v2_0) may be found at http://dx.doi.org/10.1016/j.cpc.2013.02.015.