Toward quantitative Raman spectroscopy

2nd International Conference on Chemo and Bioinformatics ICCBIKG 2023 (22-25)

АУТОР(И) / AUTHOR(S): Henryk A. Witek, Ankit Raj, Yen-Bang Chao

Е-АДРЕСА / E-MAIL: hwitek@nycu.edu.tw

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DOI: 10.46793/ICCBI23.022W

САЖЕТАК / ABSTRACT:

Raman spectra recorded using various Raman spectrometers can be quite different. The main reason for those discrepancies is the lack of a consistent calibration scheme. Our work over the past few years was devoted to finding a universal absolute calibration scheme of Raman apparatuses that would allow us to report consistent Raman spectra of molecules with an absolute intensity scale. The reported scheme is based on a carefully designed home-built Raman spectrometer, for which the conceivable sources of experimental errors have been included in the analysis, and hence eliminated. The experimental rotational and rovibrational Raman spectra of various isotopologues of molecular hydrogen (H2, HD, and D2) recorded on our apparatus are then compared to very accurate, state-of-the-art calculations of Raman cross-sections, and the comparison is used to design the final correction to the Raman intensity scale of our apparatus. The Raman spectrometer calibrated in this way is subsequently used to measure standardized Raman spectra of organic molecules, which can serve as benchmarks in the calibration of the plethora of Raman spectrometers used in chemical laboratories. Most of the experimental details of our work were already published previously (for detailed information, see the attached reference list); the current contribution focuses on theoretical aspects of our work.

КЉУЧНЕ РЕЧИ / KEYWORDS:

Raman spectroscopy, absolute intensity scale, calibration scheme, Raman cross- sections

ЛИТЕРАТУРА / REFERENCES:

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  • E. B. Wilson, J. C. Decius, P. C. Cross, Molecular Vibrations: The Theory of Infrared and Raman Vibrational Spectra, Dover Publications, New York, (1955).
  • A. Raj, H. Hamaguchi, H. A. Witek, Polarizability tensor invariants of H2, HD, and D2, J. Chem. Phys., 148 (2018) 104308 (11 pages).
  • A. Raj, H. A. Witek, H. Hamaguchi, Vibration–rotation interactions in H2, HD and D2: centrifugal distortion factors and the derivatives of polarisability invariants, Mol. Phys., 118 (2020) e1632950 (13 pages).
  • L. Wolniewicz, Relativistic energies of the ground state of the hydrogen molecule, J. Chem. Phys., 99 (1993) 1851-1868.
  • A. Raj, Y. B. Chao, H. A. Witek, Testing the limitations of harmonic approximation in the determination of Raman intensities, Mol. Phys., 120 (2022) e2069613 (19 pages).
  • A. Raj, C. Kato, H. A. Witek, H. Hamaguchi, Toward standardization of Raman Spectroscopy: Wavenumber and intensity calibration using rotational Raman spectra of H2, HD, D2 and vibration-rotation spectrum of O2 as primary standards, J. Raman Spectrosc., 51 (2020) 2066–2082.
  • A. Raj, C. Kato, H. A. Witek, H. Hamaguchi, Accurate intensity calibration of multichannel detectors using Raman intensity ratios, J. Raman Spectrosc., 52 (2021) 2038–2050.
  • Raj, H. A. Witek, H. Hamaguchi, Determination of accurate absolute Raman cross-sections of benzene and cyclohexane in the gas phase, Asian J. Phys., 30 (2021) 321–335.
  • A. Raj, H. A. Witek, H. Hamaguchi, Evaluating stability of a Raman spectrometer for long-time experiments, J. Raman Spectrosc., 52 (2021) 1032–1047.