NIST Expands Veel PC Program on Spectral Data for Transient Molecules

A major resource for physical scientists, environmental researchers, combustion engineers, and others in science and industry seeking a better understanding of various chemical processes has been expanded and now includes spectroscopic information on 1,796 short-lived molecules. This is a significant increase of more than 200 molecules from the previous version. In addition, data for the fully deuterium-substituted counterparts of these molecules are included, where available.

The NIST Vibrational and Electronic Energy Levels of Small Polyatomic Transient Molecules Database (VEEL), Version 4.0 (NIST Standard Reference Database 26) is available from the Commerce Department's National Institute of Standards and Technology.

The computer program consists of two molecular databases and the associated reference files. It is designed to provide rapid access to all published experimental data on the ground-state vibrational fundamentals of transient molecules with three to 16 atoms, and the electronic energy levels and excited-state vibrational fundamentals of transient molecules with three to six atoms, as well as of selected transient molecules with seven to 16 atoms.

NIST molecular physicist Marilyn E. Jacox points out that most chemical processes, including combustion, atmospheric pollution, industrial chemical synthesis, chemical vapor deposition and microcircuit etching, consist of a complicated sequence of elementary reactions, many of which involve free radicals, molecular ions and other short-lived reaction intermediates that react readily on collision with other molecules.

Jacox explains that each molecule has distinct emission and absorption spectra that can be detected and identified at some point during a reaction sequence. The various methods used to obtain such information on transient molecules include infrared and laser spectroscopy, magnetic resonance, flash photolysis, and conventional gas-phase ultraviolet absorption or emission spectroscopy.

Several search paths for the database are available: by molecule (formula or Chemical Abstract Service registry number); by transition wavenumber (vibrational fundamental or electronic band origin); and by wavelength range for electronic transitions. In a wavenumber search, the user also can specify a wavenumber search range.

Searches can be restricted to molecules containing a specified chemical element, to either the ground or excited electronic states, to observations of a molecule in the gas phase or in a specified inert solid matrix, or to data obtained using a specific experimental technique such as infrared absorption or laser-induced fluorescence. The user can access references for each set of information as well as all of the references associated with each molecule.

Literature references in the database are from a widely known monograph by Jacox, Vibrational and Electronic Energy Levels of Polyatomic Transient Molecules, published by the American Chemical Society as Journal of Physical and Chemical Reference Data, Monograph 3 (1994), and from other more recently published work concerned with more than 400 molecules. The monograph contains nearly all of the data in the literature before 1994.

The expanded NIST VEEL database is available for $250. Owners of a previous version can update for $50. The database requires MS-DOS 2.1 or higher with at least 512 K of RAM and 5 MB of space on the hard disk. It can be run on other types of computers having DOS emulation software.

To order NIST Vibrational and Electronic Energy Levels of Small Polyatomic Transient Molecules Database (VEEL), Version 4.0, Standard Reference Database 26, contact the Standard Reference Data Program, Building 820, Room 113, NIST, Gaithersburg, Md. 20899, (301) 975-2208, fax: (301) 926-0416, e-mail: srdata [at] enh.nist.gov (srdata[at]enh[dot]nist[dot]gov). The NIST Standard Reference Data Products Catalog can be accessed through the World Wide Webb at http://www.nist.gov/srd.

As a non-regulatory agency of the Commerce Department's Technology Administration, NIST promotes U.S. economic growth by working with industry to develop and apply technology, measurements and standards.