Infrared absorption coefficient

Cyanine and polymethine benzothiopyran dyes (e.g., 79) have been prepared.296-298 The polymethine dyes are particularly stable to heat and to light, possess high infrared absorption coefficients, and have... 

Figure 2. Measured far-infrared absorption coefficient of dry films of lysozyme...

The infrared transitions obey the following selection rules Ap — 1, and A./ = 1 or 0. The wave functions for the initial and final states obtained by solving the Schrodinger equation with the Hamiltonian of Eq. (1-261) or (1-265) can be used to compute the infrared absorption intensities for the complex. The infrared absorption coefficient J(J" ->./ ) for the transition J" J is proportional to,... 

The IR and Raman spectra are calculated by Fourier transformation of the dipole and polarizability tensor autocorrelation functions, respectively. T3s-A classical expression for the infrared absorption coefficient ct(co) at frequency CO reads ... 

Infrared methods have been used to study adsorbed species (reactants, intermediates, products), to examine species produced in the thin layer of solution between electrode and window, and to probe the electrical double layer. These approaches have been especially useful with species that have a high infrared absorption coefficients, like CO and CN . In favorable cases, information about the orientation of an adsorbed molecule and the potential dependence of adsorption can be obtained. For example, the SNIFTIRS spectrum obtained with a 0.5 mM aqueous solution of p-difluorobenzene in 0.1 M HCIO4 at a Pt electrode is shown in Figure 17.2.6 (62). The spectrum results from both dissolved (positive AR/R-values) and surface adsorbed (negative AR/R-values) p-difluorobenzene. 

Berg, J. I. "Near Infrared Absorption Coefficient of Molten Glass by Emission Spectroscopy." International Journal of Thermophysics 2, no. 4 (1981) 381-94. 

The infrared absorption coefficient and thermal wave decay coefficients, a(v) and flj, respectively, determine the magnitude of the photoacoustic signal. The term ot( exp —[a( +fls]x in the expression for temperature oscillation leads to a linear PA signal dependence on infrared absorption when a( thermal wave decay length, L, although it is sometimes referred to as the sampling depth, penetration depth, or thermal diflusion depth. The sample layer extending a distance L beneath the surface contributes... 

Tables 2,3, and 4 outline many of the physical and thermodynamic properties ofpara- and normal hydrogen in the sohd, hquid, and gaseous states, respectively. Extensive tabulations of all the thermodynamic and transport properties hsted in these tables from the triple point to 3000 K and at 0.01—100 MPa (1—14,500 psi) are available (5,39). Additional properties, including accommodation coefficients, thermal diffusivity, virial coefficients, index of refraction, Joule-Thorns on coefficients, Prandti numbers, vapor pressures, infrared absorption, and heat transfer and thermal transpiration parameters are also available (5,40). Thermodynamic properties for hydrogen at 300—20,000 K and 10 Pa to 10.4 MPa (lO " -103 atm) (41) and transport properties at 1,000—30,000 K and 0.1—3.0 MPa (1—30 atm) (42) have been compiled. Enthalpy—entropy tabulations for hydrogen over the range 3—100,000 K and 0.001—101.3 MPa (0.01—1000 atm) have been made (43). Many physical properties for the other isotopes of hydrogen (deuterium and tritium) have also been compiled (44).

Whilst nothing can improve upon the disadvantage of low molar absorption coefficients, instrumental designs and improvements with ratio recording and FT-IR instruments have virtually overcome the accuracy and instrumental limitations referred to in (b) and (c) above. As a result, quantitative infrared procedures are now much more widely used and are frequently applied in quality control and materials investigations. Applications fall into several distinct groups ... 

APPENDIX 11 CHARACTERISTIC INFRARED ABSORPTION BANDS 839 APPENDIX 12 PERCENTAGE POINTS OF THE f-DISTRIBUTION 840 APPENDIX 13 / -DISTRIBUTION 841 APPENDIX 14 CRITICAL VALUES OF 0 (/> = 0.05) 842 APPENDIX 15 CRITICAL VALUES OF THE CORRELATION COEFFICIENT p (P = 0.05) 842... 

In the preceding discussion of Beer s Law, it was argued that x-ray absorption is a simpler process than the absorption of ultraviolet, visible, and infrared wavelengths. This greater simplicity becomes particularly obvious when x-ray absorption coefficients are examined. 

The same information may be obtained from purely rotational far infrared spectroscopy (FIR) and depolarized Rayleigh spectra. Dielectric relaxation measurements are also used for the same goal, most successfully in combination with far-infrared data. The absorption coefficient of a periodic electric field... 

Cavity-enhanced absorption techniques are also applied in flames in the near infrared [22-25]. The multiple absorption paths provided with these techniques are the reason for their superb sensitivity in the ppb range. Absolute concentrations can be obtained, provided the absorption coefficient for the respective transition is known. CRDS can be used in conjunction with other laser-based combustion diagnostics for... 

Hubbard, G.L. and Tien, C.L., Infrared mean absorption coefficients of luminous flames and smoke, ASME. Heat Transfer, 100, 235,1978. 

Chemical methods for structure determination in diene pol3 mers have in large measure been superseded by infrared absorption techniques. By comparing the infrared absorption spectra of polybutadiene and of the olefins chosen as models whose ethylenic structures correspond to the respective structural units, it has been possible to show that the bands occurring at 910.5, 966.5, and 724 cm. are characteristic of the 1,2, the mns-1,4, and the m-1,4 units, respectively. Moreover, the proportion of each unit may be determined within 1 or 2 percent from measurements of the absorption intensity in each band. The extinction coefficients characteristic of each structure must, of course, be known these may be assigned from intensity measurements on model compounds. Since the proportions of the various units depend on the rates of competitive reactions, their percentages may be expected to vary with the polymerization temperature. The 1,2 unit occurs to the extent of 18 to 22 percent of the total, almost independent of the temperature, in free-radical-polymerized (emulsion or mass) poly butadiene. The ratio of trans-1,4 to cfs-1,4, however,... 

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