National Institute of Standards and Technology

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The most important numerical atomic database at NIST is the Atomic Spectra Database (ASD: It contains critically evaluated NIST data for radiative transitions and energy levels in atoms and atomic ions. Data are included for observed transitions of 99 elements and energy levels of 57 elements. ASD contains data on about 950 spectra from about 0.4 Å to 500 μm, with about 77,000 energy levels and 144,000 lines, 60,000 of which have transition probabilities. Following general principles for databasing at NIST only published and evaluated data are included and accuracy must be reported. The data are consistent between spectral lines and atomic levels, which are both in the ASD.

The database is built on MySQL RDBMS and the interface was developed at NIFS using Perl, Java and JavaScript. The interface offers some online derived data in addition to the static data. The database is heavily used; over 400,000 queries were made for spectral lines and over 135,000 for energy levels in the first 11 months of 2009. Compiling new data involves a critical evaluation of the literature, the assessment and possibly change of line identifications, the optimization of energy levels based on multiple sources, the assignment of accuracies, and an internal NIST quality review. A new compilation for Ti is almost finished, a new compilation for Ar is undergoing internal review, and work is in progress on Ba and Sr (many charge states), Ni I and II, and H, He, Li, Be, B, F, Ne and Ar I. Other compilations since 2006/2007 are concerned with Kr, Si, S, Na, Xe and Al (all many charge states) and with Hg I.

There are several bibliographical atomic databases at NIST; concerned with atomic energy levels and spectra, transition probabilities, line broadening, and energy levels and transition probabilities (integrated with ASD). The content has been enriched with direct HTML links to online papers through Digital Object Identifiers. The literature is searched automatically and updates are made on a daily basis. The number of records has grown from 20,000 in 2006 to about 30,000 now.

In addition to the Atomic Spectroscopy Database and the numerical databases the Physics Laboratory at NIST is involved in collisional radiative plasma modeling. The NLTE (non-local thermodynamic equilibrium) series of workshops, most recently NLTE-6 in Dec 2009 in Athens, Greece are organized by NIST and the results of the workshops contribute to the NIST Saha Plasma Kinetics Modeling Database ( and ), which contains benchmark results for simulation of plasma population kinetics and emission spectra. The on-line NLTE code FLYCHK ( ) is available for time-dependent and steady-state calculations of charge state distributions and spectral properties.

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