Marvin R. Querry

Optical Constants of Water in the 200-nm to 200-μm Wavelength Region

Extinction coefficients k(lambda) for water at 25 degrees C were determined through a broad spectral region by manually smoothing a point by point graph of k(lambda) vs wavelength lambda that was plotted for data obtained from a review of the scientific literature on the optical constants of water. Absorption bands representing k(lambda) were postulated where data were not available in the vacuum uv and soft x-ray regions. A subtractive Kramers-Kronig analysis of the combined postulated and smoothed portions of the k(lambda) spectrum provided the index of refraction n(lambda) for the spectral region 200 nm </= lambda </= 200 microm.

Optical properties of fourteen metals in the infrared and far infrared: Al, Co, Cu, Au, Fe, Pb, Mo, Ni, Pd, Pt, Ag, Ti, V, and W.

Infrared optical constants collected from the literature are tabulated for Mo and V. New data are presented for Cu, Fe, and Ni. Drude model parameters ωτ and ωp are given for the fourteen metals Al, Co, Cu, Au, Fe, Pb, Mo, Ni, Pd, Pt, Ag, Ti, V, and W. The Drude model parameters for Cu are revised from our earlier tabulation due to the availability of additional data. Refinements in our fitting technique have resulted in only slight changes in the Drude model parameters for Al, Au, Ag, and W. The Drude model parameters for Pb correct a numerical error in our earlier tabulation. For all fourteen metals, the optical resistivity has been calculated from the Drude model parameters ωτ and ωp and compared to handbook values for the dc resistivity.

Wedge shaped cell for highly absorbent liquids: infrared optical constants of water

We designed an improved wedge shaped cell for measuring Lambert absorption coefficient spectra alpha(nu) of highly absorbent liquids. The design allows for accurate determination of the apex angle of the wedge, sealing the cell, and injection of the liquid without disassembling the cell. We measured alpha(nu) for water through the 500-12,500-cm(-1) wavenumber region to determine the range of alpha(nu) for which the cell provided accurate measurements. We then determined the imaginary part of the complex refractive index N(nu) = n(nu) + ik(nu) from alpha(nu) and used Kramers-Kronig methods to compute n(nu) from k(nu).

Optical properties of Al, Fe, Ti, Ta, W, and Mo at submillimeter wavelengths

Measurements of the optical constants of metals at submillimeter wavelengths are sparse. We have used a nonresonant cavity to measure, at room temperature, the angle averaged absorptance spectra P(omega) of aluminum, molybdenum, tantalum, titanium, tungsten, and iron in the 30-300-cm(-1) wavenumber region. The real part of the normalized surface impedance spectrum, z(omega) = r(omega) + ix(omega), was determined from P(omega). Measurements were also made on iron from 400 to 4000 cm(-1) using standard reflectance techniques. The r(omega) spectrum was combined with previous measurements by others at higher frequencies and Kramers-Kronig analyses of the resultant combined r(omega) spectra provided epsilon(omega) = epsilon(1)(omega) + iepsilon(2)(omega) and N(omega) = n(omega) + ik(omega).

Optical properties of Au, Ni, and Pb at submillimeter wavelengths

Measurements of the optical properties, and thus the optical constants, of metals at submillimeter wavelengths are almost nonexistent. We used a nonresonant cavity to measure at ambient temperature the angle averaged absorptance spectra P(omega) of gold, nickel, and lead in the 30-300-cm(-1) wave-number region. The real part of the normalized surface impedance spectrum z(omega) = r(omega) + ix(omega) was determined from P(omega). The r(omega) spectrum was combined with previous measurements by others at higher frequencies, and Kramers- Kronig analyses of the resultant r(omega) spectra provided (omega) =, (1) (omega) + i(2)(omega) and N(omega) = n(omega) + ik(omega) for gold and nickel in the 35-15,000-cm(-1) region and for lead in the 15-15,000-cm(-1) region. We also derived an exact analytical expression for P(omega) of a metal.

Optical Constants of Water in the Infrared

The infrared reflectance of water in the region 5000–300 cm−1 has been measured at near-normal incidence and at an incidence angle of 53°. On the basis of the measured values of spectral reflectance and the existing data on spectral transmittance, we have obtained values for the real and imaginary parts of the refractive index of water. The resulting values, which are presented in both graphical and tabular form, are compared with recent determinations by other investigators.

Optical properties of calcite and gypsum in crystalline and powdered form in the infrared and far-infrared

Abstract The complex indices of refraction for crystalline gypsum and calcite were determined from reflectance measurements for both single crystals and pressed powder pellets. These optical constants were determined from a classical dispersive analysis (DA) of the reflectance data to facilitate comparisons between the crystal and powdered data. This study was done to show the usefulness and the limitations of using pressed pellets for determining the complex refractive index of materials unavailable in single crystals.

Complex refractive index of limestone in the visible and infrared

Near normal-incidence relative spectular reflectance was measured throughout the 0.2-32.8-microm wavelength region for three cut and polished samples of Bethany Falls limestone. Water, for which the complex refractive index is well known, was the reflectance standard. Although the visual appearances of the three samples were quite different, the relative reflectance spectra for the three samples were nearly identical. The three relative reflectance spectra were averaged to obtain a composite relative reflectance spectrum. Kramers-Kronig analysis of the composite relative reflectance spectrum then provided spectral values of the complex refractive index for limestone. A classical Lorentz dispersion analysis was also made of the composite relative reflectance spectrum, and the resulting dispersion parameters were tabulated. Infrared bands characteristic of the carbonate ion CO(3)(-2) of the calcite comprising the limestone appeared as strong features in the spectra.

Influence of Temperature on the Spectrum of Water

The normal-incidence spectral reflectance of water at 5, 27, and 70°C has been measured in the spectral region between 5000 and 350 cm−1. From the measured values of spectral reflectance we have determined the optical constants nr and ni by Kramers–Kronig methods. The band strengths SB = ∫ni(ν) dν and bandwidths have been determined for the absorption bands near 3400, 1640, and 600 cm−1 at each temperature. A similar study of deuterium oxide at 27°C has been conducted for purposes of comparison.

Optical properties of Bacillus subtilis spores from 0.2 to 2.5 µm

We have used spectral reflectance and transmittance measurements combined with Kramers-Krönig analyses to obtain the real (n) and imaginary (k) parts of the complex refractive index, N = n + ik, of Bacillus subtilis spores over a wavelength interval from 0.2 to 2.5 mum. Samples were in the form of thin solid films, pressed pellets, and suspensions in water and glycerol. The optical constants of spores suspended in water were found to differ from those of spores suspended in glycerol. In addition, spores previously exposed to water in earlier experiments and subsequently dried exhibited different optical constants from spores that had not been exposed to water.