Reliability of classical dispersion analysis of LiF and MgO reflectance data

Kachare, A. H.; Andermann, G.; Brantley, L. Reed

doi:10.1016/0022-3697(72)90029-7

Cited by 41 publications

(20 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Undersampling rounds the peaks. Therefore the temperature response of MgO deduced by Kachare et al (1972) has some degree of associated uncertainty. The measurements show that, for both peaks, the frequencies decrease as temperature increases (dν/d T =−0.0186 cm −1 K −1 ), whereas the damping coefficients and oscillator strengths increase.…”

Section: Discussionmentioning

confidence: 99%

“…Transverse acoustic (TA) and longitudinal acoustic (LA) modes also exist, but symmetry considerations suggest that these should not be detected by IR spectroscopy. However, IR spectra of compounds with the rocksalt structure often have weak IR modes superimposed on the one strong IR band (Kachare, Andermann & Brantley 1972). Such resonances are generally attributed to acoustic modes (Mitra 1969).…”

Section: Symmetry Analysismentioning

confidence: 99%

“…MgO reflectivity has been obtained from 8 to 1950 K (Jasperse et al 1964) and analysed using the classical dispersion model (Kachare et al 1972). However, the data at room temperature vary slightly from the present results (Fig.…”

Section: Effect Of Temperaturementioning

confidence: 99%

See 2 more Smart Citations

Absorption and reflection infrared spectra of MgO and other diatomic compounds

Hofmeister¹,

Keppel²,

Speck³

2003

Monthly Notices of the Royal Astronomical Society

160

123

View full text Add to dashboard Cite

Oxide and sulphide minerals are expected to occur in diverse astronomical environments. However, optical constants for such minerals are either lacking or poorly characterized. Minimizing errors in laboratory data, while extrapolating over wide frequency ranges, is the focus of this report. We present reflection and absorption spectra of single‐crystal MgO from about ∼100 to 18 000 cm−1 (∼100 to 0.5 μm), and derive emissivity, dielectric and optical functions (n and k) using classical dispersion analysis and supplementary data to ensure that the reflectivity values are correct at the low‐ and high‐frequency limits. Absorbance spectra of thin films of oxides (MgO, CaO, FeO and ZnO) and sulphides (MgS, CaS and FeS) are in good agreement with available reflectivity measurements, and provide information on the various effects of chemical composition, structure and optical depth. The greatest mismatch occurs for MgO, connected with this compound having the broadest peak in reflectance. The ferrous compounds (FeO and FeS) have relatively weak infrared features and may be difficult to detect in astronomical environments. Previous optical data based on transmission spectra of dispersions have underestimated the strength of the main infrared features because this approach includes spectral artefacts that arise from the presence of opaque particulates, or from non‐uniform optical depth. We show that areal coverage, not grain size, is the key factor in altering absorption spectra from the intrinsic values, and discuss how to account for ‘light leakage’ in interpreting astronomical data. Previous reflectivity data on polycrystals differ from intrinsic values because of the presence of additional, internal reflections, creating errors in the derived optical functions. We use classical dispersion analysis and supplemental data from optical microscopy to provide correct n‐ and k‐values for FeO from the far‐infrared to the visible, which can then be used in radiative transfer models. Thin‐film absorption data are also affected by internal reflections in the transparent regions: we show how to recognize these features and how to obtain the absorption coefficient, n, and k from thin‐film infrared data on CaO, CaS and MgS using the damped harmonic oscillator model.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Symmetry Analysismentioning

confidence: 99%

See 1 more Smart Citation

Absorption and reflection infrared spectra of MgO and other diatomic compounds

Hofmeister¹,

Keppel²,

Speck³

2003

Monthly Notices of the Royal Astronomical Society

160

123

View full text Add to dashboard Cite

show abstract

“…Kachare et al [89] reanalyzed these results and emphasized the superiority of using a K-K analysis of the reflectance data. Piriou and Cabannes [77] made similar specular-reflectance measurements between about 300 and 1000 cm -1 and analyzed the measurements with both a two-oscillator fit and a K-K analysis.…”

Section: Infrared Regionmentioning

confidence: 99%

Magnesium Oxide (MgO)

Roessler

1997

Handbook of Optical Constants of Solids

View full text Add to dashboard Cite

“…However, previous laboratory studies (e.g. Day 1976; Agladze et al 1996; Henning & Mutschke 1997; Mennella et al 1998) have shown that the optical properties of silicates vary between 295 and 10 K. In MgO the frequency and FWHM( ν ) of the 24.5‐μm (295‐K) TO mode (Jasperse et al 1964) vary nearly linearly with temperature between 7.5 and 1950 K (Kachare, Andermann & Brantley 1972). A similar study of the effect of temperatures on PAH bands by Joblin et al (1995) revealed changes in band structure, bandwidth and frequency which indicate that free (as opposed to condensed) PAH molecules carry the astronomical 3.3‐μm band.…”

Section: Introductionmentioning

confidence: 99%

Temperature effects on the 15-85 m spectra of olivines and pyroxenes

Bowey

Lee

Tucker

et al. 2001

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Far‐infrared spectra of laboratory silicates are normally obtained at room temperature even though the grains responsible for astronomical silicate emission bands seen at wavelengths >20 μm are likely to be at temperatures below ∼150 K. In order to investigate the effect of temperature on silicate spectra, we have obtained absorption spectra of powdered forsterite and olivine, along with two orthoenstatites and diopside clinopyroxene, at 3.5±0.5 K and at room temperature (295±2 K). To determine the changes in the spectra the resolution must be increased from ∼1 to 0.25 cm−1 at both temperatures, because a reduction in temperature reduces the phonon density, thereby reducing the width of the infrared peaks. Several bands observed at 295 K split at 3.5 K. At 3.5 K the widths of isolated single bands in olivine, enstatites and diopside are ∼90 per cent of their 295‐K widths. However, in forsterite the 3.5‐K widths of the 31‐, 49‐ and 69‐μm bands are, respectively, 90, 45 and 31 per cent of their 295‐K widths. Owing to an increase in phonon energy as the lattice contracts, 3.5‐K singlet peaks occur at shorter wavelengths than do the corresponding 295‐K peaks; the magnitude of the wavelength shift increases from ∼0–0.2 μm at 25 μm to ∼0.9 μm at 80 μm. In olivines and enstatites the wavelength shifts can be approximated by polynomials of the form ax+bx2 where x=λpk(295 K) and the coefficients a and b differ between minerals; for diopside this formula gives a lower limit to the shift. Changes in the relative absorbances of spectral peaks are also observed. The temperature dependence of λpk and bandwidth shows promise as a means to deduce characteristic temperatures of mineralogically distinct grain populations. In addition, the observed changes in band strength with temperature will affect estimates of grain masses and relative mineral abundances inferred using room‐temperature laboratory data. Spectral measurements of a variety of minerals at a range of temperatures are required to quantify these effects fully.

show abstract

Reliability of classical dispersion analysis of LiF and MgO reflectance data

Cited by 41 publications

References 7 publications

Absorption and reflection infrared spectra of MgO and other diatomic compounds

Absorption and reflection infrared spectra of MgO and other diatomic compounds

Magnesium Oxide (MgO)

Temperature effects on the 15-85 m spectra of olivines and pyroxenes

Contact Info

Product

Resources

About