Compact Table for the Publication of Infrared Spectra That are Quantitative on Both Intensity and Wavenumber Axes

1993 ◽  
Vol 47 (12) ◽  
pp. 1989-2001 ◽  
Author(s):  
John E. Bertie ◽  
R. Norman Jones ◽  
Yoram Apelblat
Keyword(s):  
Refractive Index ◽  
Absorption Coefficient ◽  
Infrared Spectra ◽  
Molar Absorption Coefficient ◽  
Full Spectrum ◽  
The Real ◽  
Original Spectrum ◽  
Detailed Method ◽  
Refractive Index Spectrum ◽  
Real Refractive Index

A Compact Table format is presented for the publication of infrared spectra that are quantitative on both intensity and wavenumber axes. The format is illustrated with a molar absorption coefficient spectrum, Em(ν˜) vs. ν˜, and with infrared real and imaginary refractive index spectra, n(ν˜) vs. ν˜ and k(ν˜) vs. ν˜, respectively. The algorithm consists of two steps: first, the number of spectral points is reduced by using larger wavenumber spacings than appear in the original spectrum; second, the resulting spectral points are presented in a compressed table format. The Compact Table is about one tenth the size required for the original spectrum to be presented in a conventional XY table. The essential criterion for increasing the wavenumber spacing is that it must be possible to recover the original spectrum by interpolation to an accuracy better than that of the original spectrum. Nearly all the recovered imaginary refractive index and molar absorption coefficient values are within 1% of the original values, and for each quantity the average of the magnitudes of the accuracies of recovery is 0.2%. The real refractive index spectrum is most accurately recovered by Kramers-Kronig transformation of the recovered imaginary refractive index spectrum. Nearly all the recovered real refractive index values are within 0.02% of the original values, and the average of the magnitudes of the accuracies of recovery is 0.005%. The real and imaginary infrared dielectric constant spectra, ɛ′(ν˜) vs. ν˜ and ɛ″(ν˜) vs. ν˜, can be calculated from the recovered data with an accuracy in ɛ′ that is about one half of that of the real refractive index and an accuracy in ɛ″ that is approximately that of the imaginary refractive index. The detailed method is outlined and is applied to infrared intensities of chlorobenzene. Computer programs are presented for the construction of the Compact Table and for the recovery of the full spectrum from the tabulated information.

Infrared Intensities of Liquids XIV: Accurate Optical Constants and Molar Absorption Coefficients between 4800 and 450 cm−1 of Chlorobenzene at 25°C from Spectra Recorded in Several Laboratories

1994 ◽  
Vol 48 (1) ◽  
pp. 144-159 ◽  
Author(s):  
John E. Bertie ◽  
R. Norman Jones ◽  
Yoram Apelblat
Keyword(s):  
Refractive Index ◽  
Absorption Coefficient ◽  
Optical Constants ◽  
Absorption Index ◽  
Molar Absorption Coefficient ◽  
Refractive Indices ◽  
The Real ◽  
Infrared Intensities ◽  
Refractive Index Spectrum ◽  
Liquid Chlorobenzene

Accurate infrared absorption intensities of liquid chlorobenzene at 25°C are presented. Their accuracy was estimated from the agreement between the intensities measured by different spectroscopists using different instruments in different laboratories and by different spectroscopists using the same instrument in the same laboratory. The spectra from different spectroscopists have been averaged, unweighted, to give intensity spectra of chlorobenzene that are presented as the best available. The results are presented as graphs and tables of the molar absorption coefficient, Em (ν˜), and the real and imaginary refractive indices, n(ν˜) and k(ν˜), between 4800 and 450 cm−1. The peak heights and the areas under the bands in the absorption index (imaginary refractive index) spectrum are reported, as are areas under the molar absorption coefficient spectrum. Absorption index, k(ν˜), and molar absorption coefficient, Em (ν˜), values are believed accurate to an average ±2.4% at the peaks of bands with kmax > 0.002 and ±3.3% at the peaks of bands with kmax < 0.002. In the baseline k(ν˜) is accurate to ∼ ±5% above 3000 cm−1 and ∼ ±2.5% below 3000 cm−1. The areas under bands in k(ν˜) and Em (ν˜) spectra for which kmax > 0.002 are accurate to ±1.3% on average. The real refractive index, n(ν˜), values are believed to be accurate to ±0.2%.

Infrared Intensities of Liquids XIII: Accurate Optical Constants and Molar Absorption Coefficients between 6500 and 435 cm−1 of Toluene at 25°C, from Spectra Recorded in Several Laboratories

1994 ◽  
Vol 48 (1) ◽  
pp. 127-143 ◽  
Author(s):  
John E. Bertie ◽  
R. Norman Jones ◽  
Yoram Apelblat ◽  
C. Dale Keefe
Keyword(s):  
Refractive Index ◽  
Absorption Coefficient ◽  
Primary Standard ◽  
Extensive Study ◽  
Absorption Index ◽  
Molar Absorption Coefficient ◽  
Weak Band ◽  
The Real ◽  
Average Accuracy ◽  
Integrated Intensities

This paper presents accurate infrared absorption intensities of liquid toluene at 25°C. The accuracy is estimated from the agreement between the intensities measured by different spectroscopists using the same instrument in the same laboratory and also by different spectroscopists in different laboratories using instruments made by different manufacturers. The average agreement between integrated intensities over specific wavenumber ranges is about ±1.8%. The spectra from the different laboratories have been averaged, unweighted, to give intensity spectra of toluene that are presented as the best available. The use of data from different instruments in different laboratories has included the influence of systematic instrumental errors, so that the precision of the intensity data presented should be a better approximation to its accuracy than would be the case from an extensive study by one person on one instrument. The results obtained agree with the only measurements that have been made against a primary standard, the estimated accuracy of which is about 6%. The results are presented as graphs and tables of the molar absorption coefficient spectrum and the real and imaginary refractive index spectra between 6500 and 435 cm−1. The peak heights and the areas under the bands in the imaginary refractive index (i.e., absorption index) and molar absorption coefficient spectra are reported. The absorption index, k(ν˜), and molar absorption coefficient, Em (ν˜), values are believed to be accurate to an average ±2.5% at the peaks of 39 strong, medium, and weak bands and ±1.9% at the peaks of 51 very weak bands below 4100 cm−1. Above 4100 cm−1, 11 very weak bands have an average accuracy of ±1.3%. The baseline k(ν˜) values are accurate to between ±3 and ±10%. The areas under bands or band groups in k(ν˜) and εm (ν˜) spectra are accurate to 2.4% on average, or 1.2% for strong, medium, and weak band groups between 3150 and 775 cm−1 with 0.002 < kmax < 0.112. The real refractive index, n(ν˜), values are believed to be accurate to 0.2%.

Infrared Intensities of Liquids XII: Accurate Optical Constants and Molar Absorption Coefficients between 6225 and 500 cm−1 of Benzene at 25°C, from Spectra Recorded in Several Laboratories

1993 ◽  
Vol 47 (7) ◽  
pp. 891-911 ◽  
Author(s):  
John E. Bertie ◽  
R. Norman Jones ◽  
C. Dale Keefe
Keyword(s):  
Refractive Index ◽  
Absorption Coefficient ◽  
Primary Standard ◽  
Molar Absorptivity ◽  
Extensive Study ◽  
Molar Absorption Coefficient ◽  
The Real ◽  
Use Of Data ◽  
Liquid Benzene ◽  
Integrated Intensities

This paper presents the results of a study to obtain accurate infrared absorption intensities of liquid benzene at 25°C. To achieve this we have determined the agreement between the intensities measured by different spectroscopists using the same instrument in the same laboratory and also by different spectroscopists in different laboratories using instruments made by different manufacturers. The agreement between integrated intensities over specific wavenumber ranges has been found to average about 2%. The spectra from the different laboratories have been averaged, unweighted, to give intensity spectra of benzene that are presented as the best available. The use of data from different instruments in different laboratories has reduced the influence of systematic instrumental errors, so that the agreement presented should be a better approximation to the accuracy of the intensities than would be the case from an extensive study by one person on one instrument. The intensity data presented agree with the only measurements that have been made against a primary standard, the evaluated uncertainty of which is about 6%. The results are presented in both graphic and tabular forms as spectra of the molar absorption coefficient, Em(ν˜), (also called the molar absorptivity, ε, formerly the extinction coefficient) and the real and imaginary refractive indices, n(ν˜) and k(ν˜), between 6225 and 500 cm−1. The peak heights and the areas under the bands in the imaginary refractive index spectrum are reported, together with the peak heights and the areas under the bands in the molar absorption coefficient spectrum. Imaginary refractive index, k(ν˜), and molar absorption coefficient, Em(ν˜), values are believed accurate to an average ±2% at the peaks of stronger bands, ±3.5% at the peaks of the weaker bands below 4100 cm−1, and ±2.5% above 4100 cm−1. The baseline k(ν˜) values are accurate to ∼10% above 1200 cm−1 and 1% to 5% below 1200 cm−1. The areas under bands or band groups in k(ν˜) and Em(ν˜) spectra are accurate to 2% on average, or 1.5% when measured above a baseline for calibration purposes. The real refractive index, n(ν˜), values are believed accurate to 0.2%.

Infrared Intensities of Liquids XV: Infrared Refractive Indices from 8000 to 350 cm−1, Absolute Integrated Intensities, Transition Moments, and Dipole Moment Derivatives of Methanol-d, at 25°C

1994 ◽  
Vol 48 (2) ◽  
pp. 176-189 ◽  
Author(s):  
John E. Bertie ◽  
Shuliang L. Zhang
Keyword(s):  
Refractive Index ◽  
Dipole Moment ◽  
Molecular Properties ◽  
Refractive Indices ◽  
The Real ◽  
Transition Moments ◽  
Refractive Index Spectrum ◽  
Integrated Intensities ◽  
Derivatives Of ◽  
Real Refractive Index

This paper reports infrared absorption intensities of liquid methanol- d, CH3OD, at 25°C, between 8000 and 350 cm−1 Measurements were made by multiple attenuated total reflection spectroscopy with the use of the CIRCLE cell, and by transmission spectroscopy with a variable-path-length cell with CaF2 windows. The results of these two methods agree excellently and were combined to yield an imaginary refractive index spectrum, k(ν˜) vs. ν˜, between 6187 and 350 cm−1. The imaginary refractive index spectrum was arbitrarily set to zero between 6187 and 8000 cm−1 where k is always less than 2 × 10−6, in order that the real refractive index can be calculated below 8000 cm−1 by Kramers-Krönig transformation. The results are reported as graphs and as tables of the real and imaginary refractive indices between 8000 and 350 cm−1, from which all other infrared properties of liquid methanol- d can be calculated. The accuracy is estimated to be ± 3% below 5900 cm−1 and ± 10% above 5900 cm−1 for the imaginary refractive index and better than ± 0.5% for the real refractive index. In order to obtain molecular information from the refractive indices, the spectrum of the imaginary polarizability multiplied by wavenumber, ν˜ vs. ν˜, was calculated under the assumption of the Lorentz local field. The area under this ν˜ spectrum was separated into the integrated intensities of different vibrations. Molecular properties were calculated from these integrated intensities—specifically, the transition moments and dipole moment derivatives of the molecules in the liquid, the latter under the harmonic approximation. The availability of the spectra of both CH3OH and CH3OD enables the integrated intensities and the molecular properties of the C-H, O-H, O-D, and C-O stretching and CH3 deformation vibrations to be determined with confidence to a few percent. Further work with isotopic molecules is needed to improve the reliability of the integrated intensities of the C-O-H(D) in-plane bending, H-C-O-H(D) torsion, and CH3 rocking vibrations.

Infrared Intensities of Liquids XVIII: Accurate Optical Constants and Molar Absorption Coefficients between 6500 and 800 cm−1 of Dichloromethane at 25°C, from Spectra Recorded in Several Laboratories

1995 ◽  
Vol 49 (6) ◽  
pp. 840-851 ◽  
Author(s):  
John E. Bertie ◽  
Zhida Lan ◽  
R. Norman Jones ◽  
Yoram Apelblat
Keyword(s):  
Refractive Index ◽  
Absorption Coefficient ◽  
Infrared Absorption ◽  
Optical Constants ◽  
Primary Standard ◽  
Molar Absorption Coefficient ◽  
The Real ◽  
Use Of Data ◽  
Infrared Intensities ◽  
Integrated Intensities

This is the last of four papers that present the detailed measnrements and results that led to the acceptance by the International Union of Pure and Applied Chemistry of Secondary Infrared Absorption Intensity Standards for liquids. In this paper accurate infrared absorption intensities of liquid dichloromethane at 25°C are presented. The accuracy was estimated from the ±1.5% average agreement of integrated intensities over specific wavenumber ranges between spectra measured by five spectroscopists in four laboratories. The use of data from different instruments in different laboratories has significantly included the effect of systematic instrumental errors. The spectra from the different spectroscopists have been averaged, unweighted, to give intensity spectra of dichloromethane that are presented as the best available. The results obtained agree with the only measurements that have been made against a primary standard, the estimated accuracy of which is about 5.5%. The spectra of the molar absorption coefficient and or the real and imaginary refractive indices are reported as tables and graphs between 6500 and 800 cm−1. Also reported are the peak heights and the areas under band groups in the molar absorption coefficient and imaginary refractive index spectra. The imaginary refractive index, k(ν˜), and molar absorption coefficient, Em(ν˜), values are believed to be accurate to an average ±2.3% over the 36 measured bands. The baseline k(ν˜) values are believed to be accurate to ∼8% below 6000 cm−1, ∼1% below 4500 cm−1, and ∼25% above 6000 cm−1, where the absorption is extremely weak. The areas under band groups in the k(ν˜) and Em(ν˜) spectra are believed to be accurate to 1.5% averaged over the 15 measured band groups and to 1.0% over the 10 band groups below 3600 cm−1. The real refractive index, n(ν˜), values are believed to be accurate to 0.2%.

Infrared Intensities of Liquids XX: The Intensity of the OH Stretching Band of Liquid Water Revisited, and the Best Current Values of the Optical Constants of H2O(l) at 25°C between 15,000 and 1 cm−1

1996 ◽  
Vol 50 (8) ◽  
pp. 1047-1057 ◽  
Author(s):  
John E. Bertie ◽  
Zhida Lan
Keyword(s):  
Refractive Index ◽  
Liquid Water ◽  
Peak Height ◽  
Dielectric Constants ◽  
The Real ◽  
Infrared Intensities ◽  
Refractive Index Spectrum ◽  
Relative Errors ◽  
Integrated Intensities ◽  
Normal Laboratory

The previously reported nonreproducibility of the intensity of the OH stretching band of liquid water has been explored. It was found that it can be eliminated in measurements with the Circle® multiple ATR cell by ensuring that the ATR rod is coaxial with the glass liquid holder. It was also found that normal laboratory temperature variations of a few degrees change the intensity by ⩽∼1% of the peak height. A new imaginary refractive index spectrum of water has been determined between 4000 and 700 cm1 as the average of spectra calculated from ATR spectra recorded by four workers in our laboratory over the past seven years. It was obtained under experimental and computational conditions superior to those used previously, but is only marginally different from the spectra reported in 1989. In particular, the integrated intensities of the fundamentals are not changed significantly from those reported in 1989. The available imaginary refractive index, k, values between 15,000 and 1 cm−1 have been compared. The values that are judged to be the most reliable have been combined into a recommended k spectrum of H2O(l) at 25 °C between 15,000 and 1 cm−1, from which the real refractive index spectrum has been calculated by Kramers–Kronig transformation. The recommended values of the real and imaginary refractive indices and molar absorption coefficients of liquid water at 25 ± 1 °C are presented in graphs and tables. The real and imaginary dielectric constants and the real and imaginary molar polarizabilities in this wavenumber range can be calculated from the tables. Conservatively estimated probable errors of the recommended k values are given. The precision with which the values can be measured in one laboratory and the relative errors between regions are, of course, far smaller than these probable errors. The recommended k values should be of considerable value as interim standard intensities of liquid water, which will facilitate the transfer of intensities between laboratories.

scholarly journals Retrieval of aerosol microphysical properties from atmospheric lidar sounding: an investigation using synthetic measurements and data from the ACEPOL campaign

2021 ◽  
Vol 14 (6) ◽  
pp. 4755-4771
Author(s):  
William G. K. McLean ◽  
Guangliang Fu ◽  
Sharon P. Burton ◽  
Otto P. Hasekamp
Keyword(s):  
Refractive Index ◽  
Effective Radius ◽  
High Spectral Resolution ◽  
Imaginary Component ◽  
The Real ◽  
Microphysical Properties ◽  
Lidar Measurements ◽  
Fine Mode ◽  
Truth Value ◽  
Real Refractive Index

Abstract. This study presents an investigation of aerosol microphysical retrievals from high spectral resolution lidar (HSRL) measurements. Firstly, retrievals are presented for synthetically generated lidar measurements, followed by an application of the retrieval algorithm to real lidar measurements. Here, we perform the investigation for an aerosol state vector that is typically used in multi-angle polarimeter (MAP) retrievals, so that the results can be interpreted in relation to a potential combination of lidar and MAP measurements. These state vectors correspond to a bimodal size distribution, where column number, effective radius, and effective variance of both modes are treated as fit parameters, alongside the complex refractive index and particle shape. The focus is primarily on a lidar configuration based on that of the High Spectral Resolution Lidar-2 (HSRL-2), which participated in the ACEPOL (Aerosol Characterization from Polarimeter and Lidar) campaign, a combined project between NASA and SRON (Netherlands Institute for Space Research). The measurement campaign took place between October and November 2017, over the western region of the USA. Six different instruments were mounted on the aeroplane: four MAPs and two lidar instruments, HSRL-2 and the Cloud Physics Lidar (CPL). Most of the flights were carried out over land, passing over scenes with a low aerosol load. One of the flights passed over a prescribed forest fire in Arizona on 9 November, with a relatively higher aerosol optical depth (AOD), and it is the data from this flight that are focussed on in this study. A retrieval of the aerosol microphysical properties of the smoke plume mixture was attempted with the data from HSRL-2 and compared with a retrieval from the MAPs carried out in previous work pertaining to the ACEPOL data. The synthetic HSRL-2 retrievals resulted for the fine mode in a mean absolute error (MAE) of 0.038 (0.025) µm for the effective radius (with a mean truth value of 0.195 µm), 0.052 (0.037) for the real refractive index, 0.010 (7.20×10-3) for the imaginary part of the refractive index, 0.109 (0.071) for the spherical fraction, and 0.054 (0.039) for the AOD at 532 nm, where the retrievals inside brackets indicate the MAE for noise-free retrievals. For the coarse mode, we find the MAE is 0.459 (0.254) µm for the effective radius (with a mean truth value of 1.970 µm), 0.085 (0.075) for the real refractive index, 2.06×10-4 (1.90×10-4) for the imaginary component, 0.120 (0.090) for the spherical fraction, and 0.051 (0.039) for the AOD. A study of the sensitivity of retrievals to the choice of prior and first guess showed that, on average, the retrieval errors increase when the prior deviates too much from the truth value. These experiments revealed that the measurements primarily contain information on the size and shape of the aerosol, along with the column number. Some information on the real component of the refractive index is also present, with the measurements providing little on absorption or on the effective variance of the aerosol distribution, as both of these were shown to depend heavily on the choice of prior. Retrievals using the HSRL-2 smoke-plume data yielded, for the fine mode, an effective radius of 0.107 µm, a real refractive index of 1.561, an imaginary component of refractive index of 0.010, a spherical fraction of 0.719, and an AOD at 532 nm of 0.505. Additionally, the single-scattering albedo (SSA) from the HSRL-2 retrievals was 0.940. Overall, these results are in good agreement with those from the Spectropolarimeter for Planetary Exploration (SPEX) and Research Scanning Polarimeter (RSP) retrievals.

Kramers–Kronig analysis on the real refractive index of porous media in the terahertz spectral range

2011 ◽  
Vol 36 (5) ◽  
pp. 778 ◽  
Author(s):  
Pertti Silfsten ◽  
Ville Kontturi ◽  
Tuomas Ervasti ◽  
Jarkko Ketolainen ◽  
Kai-Erik Peiponen
Keyword(s):  
Porous Media ◽  
Refractive Index ◽  
Spectral Range ◽  
The Real ◽  
Real Refractive Index

scholarly journals Retrieval of aerosol microphysical properties from atmospheric lidar sounding: an investigation using synthetic measurements and data from the ACEPOL campaign

2021 ◽  
Author(s):  
William G. K. McLean ◽  
Guangliang Fu ◽  
Sharon P. Burton ◽  
Otto P. Hasekamp
Keyword(s):  
Refractive Index ◽  
Effective Radius ◽  
High Spectral Resolution ◽  
Imaginary Component ◽  
The Real ◽  
Microphysical Properties ◽  
Lidar Measurements ◽  
Fine Mode ◽  
High Spectral Resolution Lidar ◽  
Real Refractive Index

Abstract. This study presents an investigation of aerosol microphysical retrievals from High Spectral Resolution Lidar (HSRL) measurements. Firstly, retrievals are presented for synthetically-generated lidar measurements, followed by an application of the retrieval algorithm to real lidar measurements. Here, we perform the investigation for an aerosol state vector that is typically used in multi-angle polarimeter (MAP) retrievals, so that the results can be interpreted in relation to a potential combination of lidar and MAP measurements. These state vectors correspond to a bimodal size distribution, where column number, effective radius, and effective variance of both modes are treated as fit parameters, alongside the complex refractive index and particle shape. The focus is primarily on a lidar configuration based on that of the High Spectral Resolution Lidar-2 (HSRL-2), which participated in the ACEPOL (Aerosol Characterization from Polarimeter and Lidar) campaign, a combined project between NASA and SRON (Netherlands Institute for Space Research). The measurement campaign took place between October and November 2017, over the western region of the USA. Six different instruments were mounted on the aeroplane: four MAPs, and two lidar instruments: HSRL-2, and the Cloud Physics Lidar (CPL). Most of the flights were carried out over land, passing over scenes with a low aerosol load. One of the flights passed over a prescribed forest fire in Arizona on the 9th of November, with a relatively higher AOD, and it is the data from this flight that is focussed on in this study. A retrieval of the aerosol microphysical properties of the smoke plume mixture was attempted with the data from HSRL-2, and compared with a retrieval from the MAPs carried out in previous work pertaining to the ACEPOL data. The synthetic HSRL-2 retrievals resulted for the fine mode in a mean absolute error (MAE) of 0.038 (0.025) μm for the effective radius, 0.052 (0.037) for the real refractive index, 0.010 (7.20 × 10−3) for the imaginary part of the refractive index, 0.109 (0.071) for the spherical fraction, and 0.054 (0.039) for the AOD at 532 nm, where the retrievals inside brackets indicate the MAE for noise-free retrievals. For the coarse mode, we find the MAE is 0.459 (0.254) μm for the effective radius, 0.085 (0.075) for the real refractive index, 2.06 × 10−4 (1.90 × 10−4) for the imaginary component, 0.120 (0.090) for the spherical fraction, and 0.051 (0.039) for the AOD. A study of the sensitivity of retrievals to the choice of prior and first guess showed that, on average, the retrieval errors increase when the prior deviates too much from the truth value. These experiments revealed that the measurements primarily contain information on the size and shape of the aerosol, along with the column number. Some information on the real component of the refractive index is also present, with the measurements providing little on absorption or on the effective variance of the aerosol distribution, as both of these were shown to depend heavily on the choice of prior. Retrievals using the HSRL-2 smoke-plume data yielded, for the fine mode, an effective radius of 0.107 μm, a real refractive index of 1.561, an imaginary component of refractive index of 0.010, a spherical fraction of 0.719, and an AOD at 532 nm of 0.505. Additionally, the single-scattering albedo (SSA) from the HSRL-2 retrievals was 0.940. Overall, these results are in good agreement with those from the SPEX and RSP retrievals.

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