TY - JOUR

T1 - The perfection of Raman spectroscopic gas densimeters

AU - Bakker, Ronald Jack

N1 - Publisher Copyright: © 2021 The Author. Journal of Raman Spectroscopy published by John Wiley & Sons Ltd.

PY - 2021/9/1

Y1 - 2021/9/1

N2 - Raman spectroscopy can be used to determine density of gases, because the energy of fundamental vibrational modes is affected by intermolecular distances. The key problem is the estimation of exact peak positions of Raman bands, because the analyses require a precision that is mostly less than the pixel resolution of modern Raman spectrometers. A new method to determine peak positions of Raman bands and atomic emission lines in a discontinuous spectrum without numerical manipulations is tested in this study: modified scanning multichannel technique. Relocation of the gratings with a Sinus Arm Drive can be performed over a distance that is only a fraction of the pixel size that allows peak position estimations with precisions smaller than the pixel resolution and to determine the uncertainty in this estimation. This uncertainty was not determined in previous studies about gas densimeters, resulting in a large variety of inconsistent data. The new method is tested with fluid inclusions in quartz. A CO2 density of 0.1477 ± 0.0006 g·cm−3 and 0.8880 ± 0.0007 g·cm−3 determined with microthermometry correspond to a Fermi dyad of 103.12 ± 0.27 cm−1 and 104.71 ± 0.26 cm−1. A CH4 density of 0.3461 ± 0.0002 g·cm−3 and 0.4011 ± 0.0001 g·cm−3 correspond to peak positions of 2910.66 ± 0.12 cm−1 and 2910.57 ± 0.12 cm−1. The error in these numbers must be regarded as the best estimated uncertainties of peak positions, which are probably slightly adjusted to higher values due to mechanical irregularities of the Sinus Arm Drive in modern Raman systems.

AB - Raman spectroscopy can be used to determine density of gases, because the energy of fundamental vibrational modes is affected by intermolecular distances. The key problem is the estimation of exact peak positions of Raman bands, because the analyses require a precision that is mostly less than the pixel resolution of modern Raman spectrometers. A new method to determine peak positions of Raman bands and atomic emission lines in a discontinuous spectrum without numerical manipulations is tested in this study: modified scanning multichannel technique. Relocation of the gratings with a Sinus Arm Drive can be performed over a distance that is only a fraction of the pixel size that allows peak position estimations with precisions smaller than the pixel resolution and to determine the uncertainty in this estimation. This uncertainty was not determined in previous studies about gas densimeters, resulting in a large variety of inconsistent data. The new method is tested with fluid inclusions in quartz. A CO2 density of 0.1477 ± 0.0006 g·cm−3 and 0.8880 ± 0.0007 g·cm−3 determined with microthermometry correspond to a Fermi dyad of 103.12 ± 0.27 cm−1 and 104.71 ± 0.26 cm−1. A CH4 density of 0.3461 ± 0.0002 g·cm−3 and 0.4011 ± 0.0001 g·cm−3 correspond to peak positions of 2910.66 ± 0.12 cm−1 and 2910.57 ± 0.12 cm−1. The error in these numbers must be regarded as the best estimated uncertainties of peak positions, which are probably slightly adjusted to higher values due to mechanical irregularities of the Sinus Arm Drive in modern Raman systems.

KW - CH

KW - CO

KW - gas densimeter

KW - scanning multichannel technique

UR - http://www.scopus.com/inward/record.url?scp=85114023219&partnerID=8YFLogxK

U2 - 10.1002/jrs.6245

DO - 10.1002/jrs.6245

M3 - Article

AN - SCOPUS:85114023219

VL - 52.2021

SP - 1923

EP - 1948

JO - Journal of Raman Spectroscopy

JF - Journal of Raman Spectroscopy

SN - 0377-0486

IS - 11

ER -