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. Program title: ris 4 Program Files doi: http://dx.doi.org/10.17632/8vjpf69zch.1 Licensing provisions: MIT Programming language: Fortran 77 and Fortran 90 Journal reference of previous version: Comput. Phys. Comm. 184 (2013) 2187 Does the new version supersede the previous version?: Yes Subprograms used: grasp 2K VERSION 1_1 Nature of problem: Prediction of level and transition isotope shifts in atoms using four-component relativistic wave functions. Solution method: The nuclear mass shifts and field shifts are treated using first order perturbation theory. The electron density and the normal and specific mass shift parameters can be expressed as ∑μ,νcμcν〈Φ(γμPJMJ)|Vˆ|Φ(γνPJMJ)〉, where Vˆ is the relevant operator and Ψ(γPJMJ)=∑ν=1McνΦ(γνPJMJ) is the configuration state expansion, where P, J and MJ are the parity and angular quantum numbers, respectively. The matrix elements, in turn, can be decomposed as sums over radial integrals multiplied by angular coefficients. The angular coefficients are calculated using routines from the grasp2K version 1_1 package 1. Reasons for new version: This new version calculates field shift electronic factors resulting from non-constant (varying) electron densities inside the nucleus. Summary of revisions: This new version uses an expression of the field shift that through a polynomial expansion of the electron density contains higher order radial moments and thus takes the varying electron density within the nuclear volume into account. Restrictions: The complexity of the cases that can be handled is entirely determined by the grasp2K package 1 used for the generation of the electronic wave functions. Unusual features: Using a reformulation of the field shift, it is possible to study the atomic energy shifts arising from changes in nuclear charge distributions, e.g. deformations. References: 1 P. Jönsson, G. Gaigalas, J. Bieroń, C. Froese Fischer, I.P. Grant, New version: Grasp2K relativistic atomic structure package, Comput. Phys. Commun. 184 (9) (2013) 2197–2203.