Display Resolution
IRVaporWare/GasPhaseQuantIR have recently been updated with faster, high-performance plotting (Objective-C) and now displays all data points. Best performance requires an Apple Silicon CPU (M-series). Although the app will run on older, Intel CPUs.
Spectral Sources
- Sharpe S.W., T.J. Johnson, R.L. Sams, P.M. Chu, G.C. Rhoderick, and P.A. Johnson. 2004. “Gas-Phase Database for Quantitative Infrared Spectroscopy”, Applied Spectroscopy, 58, no. 12, pages 1452-1461.
- Timothy J. Johnson, Luisa T.M. Profeta, Robert L. Sams, David W.T. Griffith, Robert L. Yokelson, “An Infrared Spectral Database for Detection of Gases Emitted by Biomass Burning”, Vibrational Spectroscopy, Volume 53, Issue 1, 2010, Pages 97-102.
Spectral selection
Spectra are selected by one of two methods: (1) A pull down list based on common chemical names. Be aware that many chemicals have multiple names. For instance, water can also be correctly called “dihydrogen oxide”. (2) An entry field based on the Chemical Abstract Service (CAS) number. The CAS number is a unique identifier for each chemical. CAS numbers can be up to 10 digits, separated by two hyphens, where the last digit is a checksum. For example, water is given the CAS number 7732-18-5.
X-Axis
The X-axis can be expressed as wavenumbers (cm-1) or wavelength (microns). The X-axis may be reversed (high to low) by selecting the “Reverse” check-box. The X-axis limits may be updated by (1) entering new values via the keyboard, or (2) placing the cursor/finger over the spectrum, dragging to a new point. To reset the X-axis to full spectral region, hit the reset button or type command-r.
In addition, there is a live cross-hair following the cursor that gives x-y positions.
Y-Axis (absorbance or transmittance)
- Absorbance is a dimensionless value based on the decadic (base-10) log of I/Io and depends on concentration and path length. Absorbance can also be calculated using the Naperian or base-e logarithm.
- Transmittance is dimensionless, represents the percent of light that passes through a sample, and depends on concentration and path length.
When in absorbance mode, the integrated cross-section (cm*molecule-1) is displayed st the top of the plot.
Convolving or de-resolving spectra
Spectra can be convolved using a Gaussian profile, with full-width-half-maximum (FWHM) values between 0.5 and 50 cm-1. This is equivalent to de-resolving the spectral data.
Saving spectra
macOS – Save options are available under the file menu. Each spectrum is saved along with a metadata header containing information regarding the spectrum. Spectra are saved in comma-separated, txt, two-column format. The user can save the entire spectrum or spectrum constrained by the X-axis limits.