Absorptivity of Ice I in the Range 4000–30 cm−1

Abstract

Articles you may be interested inThe infrared spectrum of ice IV in the range 4000-400 cm−1 J. Chem. Phys. 71, 4050 (1979); 10.1063/1.438173Optical spectra of orientationally disordered crystal. V. Raman spectrum of ice Ih in the range 4000-350 cm−1 P 0 SIT RON I U M C HEM 1ST R YIN A QUE 0 U S K M n 0 4 SOL UTI 0 N S 4501 identification card and a control card. The control card contains the value of the intercept (A) at point P, the decay constant >' 2, the background counts, and the number X whose value is relative to the point P=O. The program now reads data points from point B to (X-1) and performs background subtraction. THE JOURNAL OF CHEMICAL PHYSICSThe data points from the least-squares curve XD are now read in and compared point by point with curve PD until the point D is determined. The program now proceeds to find Area 1, Area 2, Area 3, and the intensity 12• The results are printed out and the program proceeds to the next data set.The absorbance of several samples of ice Ih has been measured in the range 4000-30 em-I, and scaled to that of a particular film of unknown thickness. The thickness of the film has been calculated by two methods, first from the known absorptivity at 4940 em-I, and second by equating the appropriate Kramers-Kronig integral to the known infrared contribution to the microwave refractive index. The two thicknesses agreed well and allowed the absorptivity to be obtained in the range 4000-30 em-I. The complex refractive index and permittivity and the normal incidence reflectivity have been calculated from the absorptivity. About three-quarters of the infrared contribution to the microwave refractive index is caused by the translational lattice vibrations and about 15% by the rotational vibrations; the o-H stretching bands which absorb very strongly contribute relatively little. The maximum of the density of states in the transverse acoustic branch is at 65 em-I rather than below 50 em-I as reported earlier. Below 50 cm-I the absorptivity is roughly proportional to the fourth power of the frequency. This arises because the vibrations here are short-wavelength sound waves with a density approximately proportional to the square of the frequency, and the integrated intensity of absorption by one vibration is proportional to the square of the frequency. A theory of the contribution of the translational lattice vibrations to the microwave permittivity is given based on the theory of the absorption by orientationally disordered crystals given in an earlier paper. From the theory and the experimental measurements reported in this paper the dipole-moment derivative for the relative displacement of two water molecules in ice along their line of centers (or equivalently the effective charge of a water molecule) is about 0.3 electronic charges.

Water ice growth around evolved stars

“…Then, based on the value of the size parameter of the grain, x = 2πa/λ, we either apply a coated sphere calculation (using the routine bhcoat taken from Bohren & Huffman (1983): used when x < 30) or an effective medium calculation in combination with a MIE calculation (Bohren & Huffman (1983): used when x ≥ 30) to determine the optical properties. The optical constants used in our calculations for the silicate core, the crystalline part of the ice mantle, and the amorphous part of the ice mantle were taken from respectively Suh (1999, cold silicate data), Bertie et al (1969), and a combination of Warren (1984) and Hudgins et al (1993). The data are shown in Fig.…”

Film Growth of Ice by Vapor Deposition at 128−185 K Studied by Fourier Transform Infrared Reflection−Absorption Spectroscopy: Evolution of the OH Stretch and the Dangling Bond with Film Thickness

“…To simulate the dependence of the integrated intensity of the OH db's on the film thickness, we modified the optical indexes of the crystalline ice obtained by Toon et al 36 by inclusion of the OH db vibrational mode at ν OH ) 3690 cm -1 with a damping constant γ of 15 cm -1 . Furthermore, the OH db intensity is artificially enhanced by arbitrarily setting the integrated absorptivity (Fπ 2 ) 6.86 × 10 3 cm -2 ) to 0.1% of the integrated Lambert absorptivity of the OH stretching mode obtained from Bertie et al 13 This simulation treats the OH db's as an integral part of the ice structure and the amount of OH db's is proportional to the ice film thickness. The modified dielectric function of the resulting ice structure was calculated in accordance with Klein and Furtak 44 as follows where F ) (1/π 2 ) ∫K(ν)dν,and K(ν) is the Lambert absorptivity.…”

“…The IR-RA spectra of ice micro-phases, especially in the OH stretch region, generally show a significant difference from their transmittance analogues. 13 Although this difference is due to the inherent characteristics of grazing-angle IR-RAS of strongly absorbing media, it has seriously complicated the identification of the ice micro-phases present under different temperature conditions. Our present calculations, based on the Fresnel equations for reflection coefficients and the Mie scattering method for crystalline and noncrystalline ice phases, give reasonable agreement between the observed and simulated IR-RA spectra.…”

“…[13][14][15][16][17] These studies have shown that condensation of water vapor on a cold substrate at low pressure may lead to, depending upon the deposition conditions, the formation of different noncrystalline structures below 130 K and of polycrystalline ice (pc-ice) polymorphs, Ic (cubic ice), and Ih (hexagonal ice), at a more elevated temperature.…”

Substrate-induced cooperative effects in water adsorption from density functional calculations

“…This transfer also contributes to the weakening of the O-H covalent bond of the donor molecule. 31 These effects are the reason, for example, for the redshift of the O-H stretching frequency in ice versus liquid water. This shift also correlates with a blueshift of the H-bond stretching band in ice as compared to water.…”