The new NIST Atomic Spectra Database

The new Atomic Spectra Database (ASD), Version 2.0, of the National Institu te of Standards and Technology (NIST) contains significantly more data and covers a wider range of atomic and ionic transitions and energy levels than earlier versions. AU data are integrated. It also has a new user interface and search engine. ASD contains spectral reference data which have been cr itically evaluated and compiled by NIST. Version 2.0 contains data on 900 s pectra, with about 70 000 energy levels and 91 000 lines ranging from about I Angstrom ngstrom to 200 micrometers, roughly half of which have transiti on probabilities with estimated uncertainties. References to the NIST compi lations and original data sources are listed in the ASD bibliography. A det ailed "Help" file serves as a user's manual, and full search and filter cap abilities are provided.