The NBS Data Center on Atomic Transition Probabilities is nearing completion of a critical compilation of atomic transition probability data on allowed and forbidden transitions in the elements scandium through nickel in all stages of ionization. This compilation constitutes a revision of a series of smaller NBS compilations published in recent years in the Journal of Physical and Chemical Reference Data. Upon completion of this project, work on updating of an even earlier compilation covering the elements hydrogen through neon will be initiated.

The world literature on atomic transition probabilities is collected and catalogued on an ongoing basis by the Data Center. A master reference list is maintained, and annotated bibliographies are issued as the number of new articles in the literature and the resources of the Center permit. A computerized bibliographic database system is being developed to enhance the capability for handling bibliographical information in the NBS data centers on transition probabilities, line shapes and shifts, and energy levels. Development of a computerized database of critically evaluated numerical data on atomic spectroscopic quantities is planned for the future.