Isospin splitting in double isovector excitations

Abstract
Expressions are derived for the relative locations of the different isospin components of double isovector excitations. The splittings between the isospin components are found to be similar in magnitude to the isospin splittings in single excitations. Formulas are given for the relative strengths for exciting the different isospin components of the double excitations. Energy-weighted centroids are calculated in terms of isovector and isotensor energies. Examples are given, using available data for the double giant-dipole resonance. The Lane potential is found to be similar in magnitude to that for the single giant-dipole resonance.