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Updated: Jun 16, 2026

In Situ SIMS and IR Spectroscopy of Well-defined Surfaces Prepared by Soft Landing of Mass-selected Ions
Published on: June 16, 2014
Confirmation of PNNL Quantitative Infrared Cross-Sections for Isobutane
Timothy J Johnson1, Kendall D Hughey1, Thomas A Blake1
1Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States.
Abstract:
The Pacific Northwest National Laboratory (PNNL) gas-phase database is a compilation of quantitative experimental (5, 25, and 50 °C) infrared spectra of ca. 500 molecules, designed for in situ, standoff or remote sensing of gases and vapors at or near atmospheric pressure. The data are characterized by calibration on both the wavenumber and intensity axes. Recent papers have called into question the PNNL intensity values for isobutane, [2-methylpropane, HC(CH3)3], suggesting discrepancies of 30-40%. In this study, we remeasure and re-examine the intensity values of isobutane using both similar and alternate methods to those used to generate the original PNNL database spectra. Indirect confirmation from literature data of homologous molecules and direct confirmation from new results confirm that for many band integrals across the isobutane spectrum, the original PNNL data are indeed accurate to within the reported 3% experimental uncertainty.
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