This page provides access to the theoretical information used in the numerical calculation of the energy levels and transition frequencies given by this database. Also provided is a link to a page that gives the output matrices of the 2002 CODATA least-squares adjustment. These matrices can be used obtain the data provided here. The energy level and transition frequency data may be accessed in a variety of forms as indicated by the links below.

Theory, Input Data, and Matrices
	Theory and theoretical input data	Least-squares adjustment matrices

Output Data
	Total energies	Differences of transition frequencies
	Transition frequencies

Theoretical compilation and background:                 Ulrich D. Jentschura, Svetlana Kotochigova, Eric O. Le Bigot, Peter J. Mohr, and Barry N. Taylor Database development and implementation:                 Svetlana Kotochigova and Peter J. Mohr