Kent F. Palmer

The real n (ν) and imaginary k (ν) parts of the complex refractive index Nˆ = n + i k of water at 27 °C have been determined from measurements of spectral reflectance at near-normal incidence and from measurements of the transmittance of water in carefully constructed absorption cells. Values of n (ν) are reported in graphical and tabular form for the spectral region 3800–27 800 cm−1; values of the Lambert absorption coefficient α(ν) are presented graphically and in tabular form, along with k (ν) for the region 3800–14 500 cm−1. Upper limits of k (ν) are established for the region 14 500–27 800 cm−1. The results are compared with earlier studies.

With the purpose of obtaining the real and imaginary parts of the complex refractive index N; = n + ik, we have made quantitative measurements of spectral transmission and reflection of sulfuric acid solutions in the visible and near infrared. On the basis of the results, we have obtained values for n throughout the entire region and values of k in the near infrared together with upper limits for k in the visible region. These optical constants can be used to interpret the results of polarization studies of solar radiation that has been scattered by the clouds of Venus. We have Kramers-Kronig phase-shift analysis to obtain values of n and k from reflection measurements in the intermediate infrared region (400-4000 cm(-1)). Our measurements were made at 300 K on sulfuric acid solutions having concentrations by weight of 95.6, 84.5, 75, 50, 38, and 25%. If the particles in the Venus clouds consist of liquid droplets of sulfuric acid at a temperature of 250 K, comparison of existing Venus data with our data suggests that the acid concentration is probably higher than 70%. Various possibilities are discussed.

The time dependence of the vacuum-uv emissions from xenon was studied at pressures ranging from 4 to 1000 Torr. Excitation of the atoms was provided by a low-intensity electron beam. Measurements were made at the wavelengths of the $\mathrm{Xe}(^{3}P_{1})$ resonance line, the 1500-\AA{} (first) continuum, and the 1700-\AA{} (second) continuum. Two- and three-body collision coefficients for the destruction of $\mathrm{Xe}(^{3}P_{1})$ atoms and a three-body coefficient for $\mathrm{Xe}(^{3}P_{2})$ metastables were determined. A radiative lifetime of 99 nsec for the ${1}_{u}$ molecular state was measured at the wavelength of the second continuum. The pressure dependence of the decay constants at the three wavelengths leads to the following results: The collisional deexcitation rate for the transition $\mathrm{Xe}(^{3}P_{1})$ to $\mathrm{Xe}(^{3}P_{2})$ is ${9.1\ifmmode\times\else\texttimes\fi{}10}^{3}$ ${\mathrm{sec}}^{\ensuremath{-}1}$/Torr. The three-body coefficient for $\mathrm{Xe}(^{3}P_{1})$ atoms is 46 ${\mathrm{sec}}^{\ensuremath{-}1}$/${\mathrm{Torr}}^{2}$. The three-body destruction rate of $\mathrm{Xe}(^{3}P_{2})$ metastables is 40 ${\mathrm{sec}}^{\ensuremath{-}1}$/${\mathrm{Torr}}^{2}$. The estimated uncertainty in the results is \ifmmode\pm\else\textpm\fi{}10%.

We describe a new, multiply subtractive Kramers-Kronig (MSKK)method to find the optical constants of a material from a singletransmittance or reflectance spectrum covering a small frequencydomain. The MSKK method incorporates independent measurements ofn and k at one or more reference wave-numbervalues to minimize errors due to extrapolations of the data. Anunexpected connection between the MSKK equations and the interpolationtheory allows us to derive the equations from an interpolationtheorem. We found that the locations of the reference points affectthe accuracy of the values determined for the optical constants andthat the optimal spacing of N reference data points isrelated to the zeros of a suitably transformed Chebychev polynomial oforder N. We discuss our efforts to optimize both the numberand the spacing of these reference points and apply our method to sometest spectra.