IR absorbance

With M = He, experimeuts were carried out between 255 K aud 273 K with a few millibar NO2 at total pressures between 300 mbar aud 200 bar. Temperature jumps on the order of 1 K were effected by pulsed irradiation (< 1 pS) with a CO2 laser at 9.2- 9.6pm aud with SiF or perfluorocyclobutaue as primary IR absorbers (< 1 mbar). Under these conditions, the dissociation of N2O4 occurs within the irradiated volume on a time scale of a few hundred microseconds. NO2 aud N2O4 were monitored simultaneously by recording the time-dependent UV absorption signal at 420 run aud 253 run, respectively. The recombination rate constant can be obtained from the effective first-order relaxation time, A derivation analogous to (equation (B2.5.9). equation (B2.5.10). equation (B2.5.11) and equation (B2.5.12)) yield... 

The GaAs laser used as light source emits at about 820 nm. Thus dyes in the actual sense are not needed rather, ir-absorbers for the spectmm between 750—850 nm Httie experience is available on this class of dyes, especially as far as their stabiHty is concerned, although much work has been done in this area. Also, infrared sensitive dyes and pigments, used in electrophotography, may be very suitable for WORM disks (8). 

The Si-H bond is a strong IR absorber and this property has frequently been used in quantitative studies44. Figure 14 shows the curve constructed by the use of model compounds 7 and 9. A satisfactory linear relation exists between the absorbance of the Si-H... 

Fig. 15. IR absorbances of products from the HSi(CH3)2CH2CH2< H2Cl/MejAl/CH2Cl2 model measured at 2115 cm-1 with concentration of products 5.0 x 10-2 M. The dotted line indicates the corresponding absorbance obtained from calibration curve of HSi(CH3)2CH2CH29>CH3 in CCU (Fig. 36)...

Salomon and Shirley [296] have performed Mossbauer-source experiments on Fe( Os) alloys with less than 0.1 at% osmium against a metallic Ir absorber. Their spectra were well-resolved magnetic eight-line patterns, which the authors could satisfactorily analyze using the Hamiltonian... 

The SEC mechanism demands only an isocratic (constant composition) solvent system with normally a single solvent. The most frequently used organic solvents are THF, chloroform, toluene, esters, ketones, DMF, etc. The key solvent parameters of interest in SEC are (i) solubility parameter (ii) refractive index (iii) UV/IR absorbance (iv) viscosity and (v) boiling point. Sample solutions are typically prepared at concentrations in the region of 0.5-5 mg mL-1. In general an injection volume of 25-100p,L per 300 x 7.5 mm column should be employed. For SEC operation with polyolefins chlorinated solvents (for detector sensitivity and increased boiling point) and elevated temperatures (110 to 150 °C) are required to dissolve olefin polymer. HFIP is the preferred solvent for SEC analysis of polyesters and polyamides. 

More than 200 users annually consume over US 55 million of light stabilisers. IR absorbers (e.g. amine, antimony salt mixture) protect against IR radiation applicable in PC, PMMA, PVC, etc. 

IR absorbance was measured with a Fourier-transform IR spectrometer. The absorbance at wave number a is defined as (1 /TV) In [F(U0)/ F(U)], where N 10 is the number of useful reflections at the electrochemical interface, F(U) the light intensity at wave number a reaching the detector at potential U, and F(U0) the same but under reference conditions at potential U0. 

Figure 3.4. Change in IR absorbance of ra-GaAs/ 6 M HC1 interface when the applied potential is changed from —0.3 to —0.8 vs. Ag/AgCl (1500 cycles of 12 s). (After Erne et al. 1998.)...

Figure 12 (a) Mid-IR absorbance spectra recorded from the thermal degradation of PMMA... 

Figure 15 IR absorbance spectra of PP films after ageing in air at 70°C (dashed curve) and after ageing at 70°C and re-processing (solid curve). Reprinted from Jansson et al. [42]. Copyright 2004, with permission from Elsevier.

The simplest IR sensor would consist of a source, a sample interface and a detector. Although quite sensitive, such an arrangement would have no selectivity as any IR absorbing substance would cause an attenuation of the detected radiation. To get the selectivity that is a main driving force behind the application of IR systems, the radiation has to be spectrally analysed. This can be accomplished either by measurement at discrete wavelengths or, for multi-component sensors or samples containing (potentially) interfering substances, by full spectral analysis of the collected radiation. 

Smoke and/or vapors do not absorb radiation as significantly in the IR spectrum as in the UV spectrum. This makes devices of this type particularly useful when heavy smoke concentrations may accompany a fire. However, care must be taken that thick IR absorbing dusts are not part of the hazard. 

Information overload, 21 613 Information science, 11 13 Information storage/read out, in molecular recognition, 16 769 Informed opinion technique, 15 637 Infrared (ir)-absorbing gases, in... 

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