Absorption decadic linear coefficient

In case the internal absorbance is divided by the optical absorption pathlength, the decadic linear absorption coefficient is given in units of cm". It is usually used at the examination of thin films because in such cases it is difficult to determine molar concentrations. In Table 2 all these terms and symbols are defined according to the lUPAC recommendations [14] and given with their units. Further terms and symbols for physical quantities, related to fundamental processes occurring in light sources, and general principles of nomenclature standardization are stated in other lUPAC recommendations of the Analytical Division [21]. 

IR spectra are given as products (< )/i(time domain, i.e., each term of the correlation function C(t) is multiplied by a Gaussian function exp —0.5a(tlt, axf ), where is the length of the simulation, and a is usually chosen around a value of 10 for gas phase simulations. This convolution only has the purpose to remove the numerical noise arising from the finite length of the Fourier transform of (5). These calculations are performed with our home-made code. 

In these equations, d is the sample thickness, e is the molar decadic absorption coefficient and c stands for the concentration. For pure samples, e-c should be replaced by a, which is the linear decadic absorption coefficient of the sample. For a black body radiator, the emission factor is ejf = 1. 

In conventional Raman spectroscopy Raman spectra are recorded from colorless samples with exciting radiation in the visible range of the spectrum. In this case, the absorption of the exciting and Raman radiation by the sample is at its minimum, and the linear decadic absorption coefficient (a = e c) is of the order of 10 -. ..10cm. ... 

Figure 3.5-3 Linear decadic absorption coefficient of H2O, D2O, Ethanol, and Cyclohexane in the near infrared region. Insertion range of the Raman spectrum, excited by the NdrYAG laser with radiation of A = 1064 nm.

In the region of NIR FT Raman spectroscopy, at F = 5000...10000 cm , substances with X-H bonds (X = any element) show overtones and combinations of the normal frequencies. They may have considerable intensity as demonstrated by Fig. 3.5-3 with the NIR absorption spectra of liquid H2O, D2O, ethanol, and cyclohexane. The linear decadic absorption coefficient a of water at a Raman shift of about 2500 cm is of the order of 10. The transmission of a layer of d = 1 cm is given by ... 

As the local electric field in the particles is enhanced at the SPR, the metal nonlinear optical response can be amplified as compared to the bulk solid one. Moreover, the intrinsic nonlinear properties of metals may themselves be modified by effects linked with electronic confinement. These interesting features have led an increasing number of people to devote their research to the study of nonlinear optical properties of nanocomposite media for about two decades. Tire third-order nonlinear response known as optical Kerr effect have been particularly investigated, both theoretically and experimentally. It results in the linear variation of both the refraction index and the absorption coefficient as a function of light intensity. These effects are usually measured by techniques employing pulsed lasers. 

Point (a) is best optimised by experiment, although several attempts have been made to provide a theoretical basis for determining the optimum concentration of a species of known molar decadic absorption coefficient for resonance Raman studies. The deleterious effects on the signal-noise ratio of the Raman spectram attributable to point (b) can be obviated by spinning the sample at ca. 1600 rev min as a solid, liquid or gas. Several articles contain details of many of these devices, the common object of which is to ensure relative motion between the sample and the focused laser beam (64). Surface scanning devices are also in use, and these enable the laser beam, while remaining focused on the surface of the sample, to scan over its surface in either a circular or linear fashion to achieve the same object. Such a procedure is particularly effective when the sample is held at liquid nitrogen temperatures. A device which allows this mode of operation is shown in Fig. 10 in this case the laser beam... 

The quantity Bf23Q3 can be written as A and is known as the decadic absorbance, or simply as the absorbance. This is the term recommended in the SI (see Appendix A). However the terms decadic extinction and optical density are still commonly used, and the student should be familiar with them. The quantity h/2.303 (i.e., the absorbance divided by the light path) is called the linear decadic absorption coefficient and usually is given the symbol a. Thus equation (2.9) can be written as... 

As demonstrated above this system of linear equations can be simplified using vectors and matrices. The absorbances measured at the three wavelengths give the vector E. The concentrations of the three components A, B, and C produce the vector of concentrations a. Finally the nine molar decadic absorption coefficients of the three components at the three wavelengths of measurement form a matrix e in eq. (4.5), whereby... 

Table 2.28 summarizes literature data on the absorption coefficients of hydroxyls on sUica and zeolites. The most commonly used dimension is cm pmoP. The decadic absorption coefficient is more prevalent than the Napierian and is usually used in IR spectroscopy. In older references, one can encounter that the linear intensity was analyzed and the absorption coefficient was expressed in cm pmol. To avoid any confusion, we shall not present such data here. 

According to the above-mentioned effect of polarization, in principle each molecule exhibits absorption at different wavelengths and intensity distributions. Bouguer, Lambert, and Beer realized many years ago a correlation between the number of particles, their properties, and the optical pathlength through a cell. It is described by a linear dependency between the attenuation and the concentration, whereby the molar decadic absorption coefficient e is derived as the proportionality constant speciflc to the molecular properties of the molecules analyzed [2,12,13]. This so-called Lambert-Beer law allows quantitative analysis of gaseous, liquid, or solid samples by absorption spectrometry. 

The term Bouguer-Lambert law is not familiar to many spectroscopists. The term Beer-Lambert law or merely Beer s law is frequently used in its place. Technically, Beer s law refers to the observation that the contribution of an absorber to the absorbance of a sample is proportional to the concentration of the absorber. The symbol k is referred to by some spectroscopists as the Beer-Lambert absorption coejficient. Because of the possibility of decadic or napierian absorbance and the various units by which concentration can be expressed, several different quantities are all Beer-Lambert absorption coefficients. The term absorptivity is commonly used in equations for decadic absorbance and can include concentration in any rmits. The term linear absorption coefficient is the usual name for the linear napierian absorption coefficient of a pure material. 

Here, Sj, S2 nd 2 e the molar decadic absorption coefficients and the refractive indices for a linearly polarized light beam with a polarization parallel and perpendicular to the optical axis of a uniaxial sample, and are the absorption coef-... 

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