Absorption distance

Spectral discrimination (9) and specific gas detection can be modeled if one assumes the gas absorbs photons of a specific wavelength exponentially with distance into the gas (Beet s law). When the absorption distance is x (cm), the incident it power density at the detector in the spectral band pass is J (W/cm ) and the power density incident on the gas is the gas concentration, C (ppm) is given by ... 

An important feature of the use of soft radiation is that both the extinction distance and the absorption distance are small, and therefore the X-rays penetrate only a veiy small distance into the crystal. We therefore examine only a small slice of the crystal close to the surface. The strain fields of dislocations deeper into the crystal do not contribute significantly to the image and, in a transmission experiment, overlapping of the images leads to an upper limit of about 10" cm on the dislocation density for individual defect imaging. With the Berg-Barrett technique this can be pushed to about 10 cm ... 

For this particular choice of canopy density, Lc = 5 m the magnitude of the perturbations induced by the hill are of order the hill slope, H/L. In a canopy with hc = 20 m this corresponds to a Leaf Area Index (LAI) of 4. If LAI = 2 but the other parameters remain unchanged, the magnitude of the perturbation terms all double because the ratio of the momentum absorption distance Lc to the hill lengthscale L plays an important dynamic role in determining the velocity perturbations that drive the scalar fluctuations in the canopy. 

E. Reduce injuries from falls and impact 1. Increase area of impact force 2. Increase energy absorption distance... 

As mentioned earlier, PAS is a good tool for studying the optical and thermal properties of a sample. Hence, this technique can be applied to fields of dermatological research such as drug detection and drug diffusion studies in skin, and thermal properties and water content of the skin. The optical and thermal properties of the sample are characterized by the optical absorption distance, and the thermal diffusion distance, /Xg. The optical absorption distance is the inverse of the optical absorption coefficient /3. The thermal diffusion length is defined by... 

EXAFS Extended X-ray absorption fine structure spectroscopy. A spectroscopic technique which can determine interatomic distances very precisely. 

EXAFS Extended x-ray absorption fine structure [177, 178] Variation of x-ray absorption as a function of x-ray energy beyond an absorption edge the probability is affected by backscattering of the emitted electron from adjacent atoms Number and interatomic distance of surface atoms... 

In this fonn it is clear that k leads to an attenuation of the electric field amplitude with distance (i.e. absorption). 

Sketch potential energy curves for the following states of CdH, Br/ and CH, given their intemuclear distances r, and suggest qualitative intensity distributions in the v" = 0 progressions for transitions between the states observed in absorption ... 

Fig. 1. Approximate relationship between sound pressure level and distance as a function of room absorption. Numbers on the curves are metric sabins.

Thickness. The traditional definition of thermal conductivity as an intrinsic property of a material where conduction is the only mode of heat transmission is not appHcable to low density materials. Although radiation between parallel surfaces is independent of distance, the measurement of X where radiation is significant requires the introduction of an additional variable, thickness. The thickness effect is observed in materials of low density at ambient temperatures and in materials of higher density at elevated temperatures. It depends on the radiation permeance of the materials, which in turn is influenced by the absorption coefficient and the density. For a cellular plastic material having a density on the order of 10 kg/m, the difference between a 25 and 100 mm thick specimen ranges from 12—15%. This reduces to less than 4% for a density of 48 kg/m. References 23—27 discuss the issue of thickness in more detail. 

Physical Properties. The absorption of x-rays by iodine has been studied and the iodine crystal stmcture deterrnined (12,13). Iodine crystallizes in the orthorhombic system and has a unit cell of eight atoms arranged as a symmetrical bipyramid. The cell constants at 18°C (14) are given in Table 1, along with other physical properties. Prom the interatomic distances of many iodine compounds, the calculated effective radius of the covalently bound iodine atom is 184 pm (15). 

Another area of research ia laser photochemistry is the dissociation of molecular species by absorption of many photons (105). The dissociation energy of many molecules is around 4.8 x 10 J (3 eV). If one uses an iafrared laser with a photon energy around 1.6 x 10 ° J (0.1 eV), about 30 photons would have to be absorbed to produce dissociation (Eig. 17). The curve shows the molecular binding energy for a polyatomic molecule as a function of interatomic distance. The horizontal lines iadicate bound excited states of the molecule. These are the vibrational states of the molecule. Eor... 

Unlike PMDs having a single chromophore, the absorption band of a bis-dye spHts into two components, so that one maximum is shifted bathochromicaHy and the other hypsochromicaHy with respect to the absorption maximum of the parent dye. The distance between bis-dye maxima depends on the magnitude of the chromophore interaction. Interaction of this kind has been discovered to be universal (45,46). 

The N—O bond distances, found to be 0.133 to 0.139 nm for trimethyl amine oxide (1), are somewhat shorter than the single N—C bond distance of 0.147 nm ia methylamine. The N—C bond distance of 0.154 nm ia trimethyl amine oxide approaches that of the C—C bond. This is ia agreement with the respective absorptions ia the iafrared region valence vibrations of N—O bonds of aUphatic amine oxides are found between 970 920 cm (2). 

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