On properties of the discrete and continuous spectrum for the radial dirac equation

To characterize the Dirac radial equation spectrum, we introduce the notion of a quantum defect _k, which is a generalization of this notion for the Schrödinger radial equation. The existence of _k is proved and explicit formulas for calculating _k are found for a broad class of potentials.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 108, No. 1, pp. 36–49, July, 1996.