Spectral signatures of solids and liquids on different substrates: the need for accurate optical constants

Myers, Tanya L.; Tonkyn, Russell G.; DeVetter, Brent M.; Danby, Tyler O.; Scharko, Nicole K.; Oeck, Ashley M.; Loring, John S.; Su, Yin‐Fong; Johnson, Timothy J.

doi:10.1117/12.2321318

Cited by 2 publications

(2 citation statements)

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“…Almost all the spectra were obtained from pure liquids (except for the aqueous solutions) or, in the case of solids, pure chemicals diluted in KBr pellets. Some of the spectra have been reported previously, some in open literature publications 4,30,[37][38][39][40] and/or as part of publicly available datasets, 1,5,37,41,42 adaptable to multiple experimental designs. The one common factor is that all of the data were acquired at high spectral resolution, i.e., 2.0 cm −1 for all samples.…”

Section: Pnnl Spectral Librariesmentioning

confidence: 99%

“…[26][27][28][29] One of the design criteria for this study was to take advantage of the available IR spectra in extant Pacific Northwest National Laboratory (PNNL) databases. 5,30 In addition to a large number of chemicals and spectra, all PNNL spectra were calibrated and acquired using well-documented procedures as summarized below. The results are in part validated by the high fidelity of the reference data, and we exploit these properties: For example, in the PNNL liquids and solids spectral databases, all data were recorded at higher spectral resolution than might be expected for field data, i.e., at resolutions narrower than the natural bandwidths so the reported resolutions represent intrinsic linewidths with negligible contributions from the instrumental lineshape.…”

Section: Introductionmentioning

confidence: 99%

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Optimal Spectral Resolution for Infrared Studies of Solids and Liquids

Forland,

Hughey,

Wilhelm

et al. 2024

Appl Spectrosc

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Due to a legacy originating in the limited capability of early computers, the spectroscopic resolution used in Fourier transform infrared spectroscopy and other systems has largely been implemented using only powers of two for more than 50 years. In this study, we investigate debunking the spectroscopic lore of, e.g., using only 2, 4, 8, or 16 cm−1 resolution and determine the optimal resolution in terms of both (i) a desired signal-to-noise ratio and (ii) efficient use of acquisition time. The study is facilitated by the availability of solids and liquids reference spectral data recorded at 2.0 cm−1 resolution and is based on an examination in the 4000–400 cm−1 range of 61 liquids and 70 solids spectra, with a total analysis of 4237 peaks, each of which was also examined for being singlet/multiplet in nature. Of the 1765 liquid bands examined, only 27 had widths <5 cm−1. Of the 2472 solid bands examined, only 39 peaks have widths <5 cm−1. For both the liquid and solid bands, a skewed distribution of peak widths was observed: For liquids, the mean peak width was 24.7 cm−1 but the median peak width was 13.7 cm−1, and, similarly, for solids, the mean peak width was 22.2 cm−1 but the median peak width was 11.2 cm−1. While recognizing other studies may differ in scope and limiting the analysis to only room temperature data, we have found that a resolution to resolve 95% of all bands is 5.7 cm−1 for liquids and 5.3 cm−1 for solids; such a resolution would capture the native linewidth (not accounting for instrumental broadening) for 95% of all the solids and liquid bands, respectively. After decades of measuring liquids and solids at 4, 8, or 16 cm−1 resolution, we suggest that, when accounting only for intrinsic linewidths, an optimized resolution of 6.0 cm−1 will capture 91% of all condensed-phase bands, i.e., broadening of only 9% of the narrowest of bands, but yielding a large gain in signal-to-noise with minimal loss of specificity.

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