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Gas-Phase Databases for Quantitative Infrared Spectroscopy

Volume 58, Number 12 (Dec. 2004) Page 1452-1461

Sharpe, Steven W.; Johnson, Timothy J.; Sams, Robert L.; Chu, Pamela M.; Rhoderick, George C.; Johnson, Patricia A.


The National Institute of Standards and Technology (NIST) and the Pacific Northwest National Laboratory (PNNL) are each creating quantitative databases containing the vapor-phase infrared spectra of pure chemicals. The digital databases have been created with both laboratory and remote-sensing applications in mind. A spectral resolution of ≊0.1 cm-1 was selected to avoid degrading sharp spec- tral features, while also realizing that atmospheric broadening typ- ically limits line widths to 0.1 cm-1. Calculated positional (wave- number, cm-1) uncertainty is ≤0.005 cm-1, while the 1σ statistical uncertainty in absorbance values is <2% for most compounds. The latter was achieved by measuring multiple (typically ≥9) path length-concentration burdens and fitting a weighted Beer's law plot to each wavenumber channel. The two databases include different classes of compounds and were compared using 12 samples. Though these 12 samples span a range of polarities, absorption strengths, and vapor pressures, the data agree to within experimental uncertainties with only one exception.