Contents of the NIST Atomic Spectra Database

The Atomic Spectra Database (ASD) contains data for atom and ion transitions, and energy levels. Lines are included for the first 99 elements in the periodic table. The energy level tables also contain ionization limits. ASD contains data on about 950 spectra, with about 144,400 lines from 0.4 to 5,000,000 angstroms in wavelength, plus about 77,000 energy levels. Except where noted, the data have been critically evaluated by NIST.

For Z=1 to 28, wavelengths, transition-probabilities, relative intensities, and energy levels are integrated, so that all the available information for a given transition is incorporated under a single listing. The wavelengths are derived from these energies unless more precise observed values are available.

The contents of ASD are limited to data which have been critically compiled by NIST, or, in the case of those energy levels compiled by R. L. Kelly, published in the Journal of Physical and Chemical Reference Data for NIST. In this sense we include only NIST ``Standard Reference Data.'' In the case of transition probabilities, for example, this means that the listed values are estimated by NIST to have the accuracies assigned to each transition. In the case of energies and wavelengths, the critically evaluated accuracies are implied by the number of significant figures. Thus all the data in ASD are of known or estimated accuracy. In some cases, this limitation to NIST-evaluated data means that the data do not reflect the most current or accurate values, because NIST evaluations have not been performed sufficiently recently to include them. For example, the NIST transition probabilities for H through B and F through Ne were published in 1966, and Na through Ca were published in 1969. These data are presently being newly evaluated and extended by roughly an order of magnitude. Also, the energy levels and wavelengths are being evaluated for H through Ne, plus Cl and Ar.

Citations for the compilations and literature sources contained therein are listed in the Bibliography.

NIST Atomic Spectra Database page