Abstract
Previous Kramers–Kronig dispersion analyses of the LiF infrared reflectance band gave physically impossible results; significant portions of the phase angle and absorption-index spectra are distorted and/or are negative. The published reflectance data have been carefully evaluated; this indicated errors in the construction of the reflectance curve in the low-reflectance region. A new method has been developed for the construction of the difficult low-reflectance curve. This method employs the mean-value integral theorem and the concept of central frequency. Selfconsistency is achieved by forcing the Kramers–Kronig output-phase-angle values to agree with phase-angle values calculated from reliable optical-index values measured outside of the difficult low-reflectance region. The final Kramers–Kronig analysis yields for the first time a phase-angle spectrum which is physically plausible and absorption-index values which are in excellent agreement with experimental measurements.
© 1968 Optical Society of America
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