Abstract
The screening constant in the double Rydberg formula is estimated using the intrashell configuration-interaction states. Its explicit dependence on the bending rovibrational quantum numbers is included. Comparison of the energy levels so obtained with elaborate numerical results indicates its utility for doubly excited states of highly charged ions and also points to its geometrical origin. Procedures are introduced to generalize the formula to intershell doubly excited states and to doubly excited states of multielectron atoms. A number of specific numerical results are presented.