Infrared Intensities of Liquids XI: Infrared Refractive Indices from 8000 to 2 cm−1, Absolute Integrated Intensities, and Dipole Moment Derivatives of Methanol at 25°C

1993 ◽  
Vol 47 (8) ◽  
pp. 1100-1114 ◽  
Author(s):  
John E. Bertie ◽  
Shuliang L. Zhang ◽  
Hans H. Eysel ◽  
Shipra Baluja ◽  
M. Khalique Ahmed
Keyword(s):  
Refractive Index ◽  
Dipole Moment ◽  
Attenuated Total Reflection ◽  
Refractive Indices ◽  
The Real ◽  
Molar Polarizability ◽  
Infrared Intensities ◽  
Integrated Intensities ◽  
Real Refractive Index ◽  
Better Than

This paper reports infrared absorption intensities of liquid methanol at 25°C between 8000 and 2 cm−1. Measurements were made by attenuated total reflection spectroscopy by four different workers between 1984 and 1991, with the use of CIRCLE cells of two different lengths and with several different alignments of the cell in the instrument. Steps were taken to ensure that as few parameters as possible remained unchanged throughout the series of measurements, to try to reveal systematic errors. The reproducibility was better than ±2.5% in regions of significant absorption. In order to allow comparison between different methods, results of all methods were converted to real and imaginary refractive index spectra. Measurements were also made by transmission spectroscopy in regions of weak absorption, with results that agreed excellently with those from ATR. The ATR and transmission results were combined to give a spectrum between 7500 and 350 cm−1. This spectrum agreed excellently with literature results from 350 to 2 cm−1, and the two sets of measurements were combined to yield a spectrum from 7500 to 2 cm−1. The imaginary refractive index was arbitrarily set to zero between 7500 and 8000 cm−1, where it is always less than 2 × 10−6, in order that the real refractive index can be calculated below 8000 cm−1 by Kramers-Kronig transform. The results are reported as graphs and as tables of the real and imaginary refractive indices between 8000 and 2 cm−1, from which all other infrared properties of liquid methanol can be calculated. The accuracy is estimated to be ±3% below 5000 cm−1 and ±10% above 5000 cm−1 for the imaginary refractive index and better than ±0.5% for the real refractive index. To obtain molecular information from the measurements, one calculates the imaginary molar polarizability spectrum, [Formula: see text] vs. [Formula: see text], under the Lorentz local field assumption, and the area under [Formula: see text] bands is separated into contributions from different vibrations under several approximations. Much accuracy is lost in this process. The changes of the dipole moment during normal vibrations, and during OH, CH, and CO bond stretching and COH torsional motion, are presented.

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 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.

Infrared Intensities of Liquids X: Accuracy of Current Methods of Obtaining Optical Constants from Multiple Attenuated Total Reflection Measurements Using the CIRCLE Cell

1992 ◽  
Vol 46 (11) ◽  
pp. 1660-1665 ◽  
Author(s):  
John E. Bertie ◽  
Shuliang L. Zhang ◽  
Rizwan Manji
Keyword(s):  
Acetic Acid ◽  
Optical Constants ◽  
Glacial Acetic Acid ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Refractive Indices ◽  
Pure Liquid ◽  
Multiple Reflections ◽  
The Real ◽  
Infrared Intensities

The literature description of the Bertie-Eysel method for obtaining the optical constants (i.e., the real and imaginary refractive indices) of liquids from multiple attenuated total reflection measurements using the CIRCLE cell is brought up to date in this paper. The accuracy of the computation methods is explored by analyzing pATR spectra which are themselves calculated from known k(ν˜) spectra that contain single Lorentzian bands, and the corresponding known n(ν˜) spectra, and also from simulated, known, n(ν˜) and k(ν˜) spectra of pure liquid methanol and glacial acetic acid. The optical constants are recovered from the pATR spectra and compared with the known originals. It is shown that k(ν˜) spectra that contain k(ν˜) values up to 0.8, 0.7, and 0.6 can be obtained accurately when the real refractive indices are near 1.3, 1.4, and 1.5, respectively. The method is, thus, reliable for spectra that can be accurately measured from the multiple reflections in the CIRCLE cell. It is likely to be troublesome for higher values of the real and the imaginary refractive indices. However, these are best measured by single-reflection methods, and more direct ways of computing the optical constants are available for such methods.

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 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%.

Optical Constants and Dipole Moment Derivatives of Bromobenzene between 3200 and 400 cm−1 at 25 °C

1998 ◽  
Vol 52 (8) ◽  
pp. 1062-1072 ◽  
Author(s):  
C. Dale Keefe ◽  
Janet Pittman
Keyword(s):  
Dipole Moment ◽  
Optical Constants ◽  
Refractive Indices ◽  
Normal Coordinates ◽  
Molar Polarizability ◽  
Ft Ir ◽  
Transmission Measurements ◽  
Integrated Intensities ◽  
Derivatives Of ◽  
Absorbance Spectra

The optical constants (real and imaginary refractive indices) of bromobenzene were determined at 25 °C via transmission measurements. Experimental absorbance spectra measured on a Nicolet Impact 410 FT-IR were converted to imaginary refractive indices by using methods described in the literature. The real refractive indices were obtained by Kramers-Kronig transformation of the imaginary refractive indices. The complex refractive indices were used to calculate the molar absorption coefficient ( Em) and complex molar polarizability (m) spectra. The integrated intensities and dipole moment derivatives with respect to normal coordinates for the fundamentals were obtained from the areas under the bands in the α“m spectrum. These dipole moment derivatives were compared to those obtained from the spectra of chlorobenzene in the literature. It was found that, in general, the dipole moment derivatives displayed very little dependence on the substituent, even for some of the vibrations for which the wavenumber is substituent sensitive.

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 Effect of 3D Printing Parameters on the Refractive Index, Attenuation Coefficient, and Birefringence of Plastics in Terahertz Range

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Alexander T. Clark ◽  
John F. Federici ◽  
Ian Gatley
Keyword(s):  
Refractive Index ◽  
3D Printing ◽  
Attenuation Coefficient ◽  
Refractive Indices ◽  
Attenuation Coefficients ◽  
Layer Height ◽  
Nozzle Size ◽  
3D Printed ◽  
Printing Parameters ◽  
Real Refractive Index

The refractive indices, attenuation coefficients, and level of birefringence of various 3D printing plastics may change depending on the printing parameters. Transmission terahertz time-domain spectroscopy was used to look for such effects in Copolyester (CPE), Nylon, Polycarbonate (PC), Polylactic acid, and Polypropylene. The thickness of each sample was measured using an external reference structure and time-of-flight measurements. The parameters varied were printer nozzle size, print layer height, and print orientation. Comparison of these parameters showed that a printer’s nozzle size and print layer height caused no change in real refractive index or attenuation coefficient. A change in printing orientation from vertical to horizontal caused an increase both in real refractive index and in attenuation coefficient. In vertically printed samples, the increase in birefringence was proportional to the increase in layer height and inversely proportional to nozzle size. There was no measurable intrinsic birefringence in the horizontally printed samples. These effects should be taken into account in the design of FDM 3D printed structures that demand tailored refractive indices and attenuation coefficients, while also providing a foundation for nondestructive evaluation of FDM 3D printed objects and structures.

Sign in / Sign up

Export Citation Format

Share Document