This paper presents quasinormal-mode frequencies for Reissner-Nordström black holes calculated using the phase-integral approximation. It is shown that the eigenfrequencies of the first modes (those with small imaginary parts) are accurately determined by the so-called Bohr-Sommerfeld formula. The formula generates frequencies with roughly the same accuracy as obtained in the Schwarzschild case except when the charge is close to its limiting value. For higher modes a generalized formula, recently derived by the present authors, is used. Numerical calculations show that, while it is reasonably accurate for low charges, this formula cannot be trusted for high charges. An intrinsic estimate of the error in the phase-integral calculations is also discussed.

• Received 3 February 1993

DOI:https://doi.org/10.1103/PhysRevD.49.2703