Absorption coefficient saturated

For optical detection, the product to be determined must have a reasonable absorption coefficient. Saturation ofthe pyrimidine C(5)-C(6) bond destroys the chromophore, and for the determination of Tg yields excreted into the urine, this product was reduced with HI into Thy prior to an HPLC analysis (Cathcart et al. 1984). 

Applications Involving Nonlinear Absorption Phenomena. Saturable absorption (hole-burning) is a change (typically a decrease) in absorption coefficient which is proportional to pump intensity. For a simple two level system, this can be expressed as... 

Reverse saturable absorption is an increase in the absorption coefficient of a material that is proportional to pump intensity. This phenomenon typically involves the population of a strongly absorbing excited state and is the basis of optical limiters or sensor protection elements. A variety of electronic and molecular reorientation processes can give rise to reverse saturable absorption many materials exhibit this phenomenon, including fuUerenes, phthalocyanine compounds (qv), and organometaUic complexes. 

Noteworthy is the behaviour of some dyes, for example indanthrone dyes, which become opaque with high-power laser irradiation in contrast to the normal saturation of absorption discussed above 15>. It could be shown that in these cases photochemical processes are operative, creating species which exhibit a higher absorption coefficient at the laser wavelength 18>. 

Most of the functional groups obtained in this work have very high absorption coefficients comparatively with the parent functions and this technique can also be usefull to improve their detection in polymer matrix. From this point of view, reactions as saturation of double bonds or oxidation of NH group into nitroxyl radical can allow to follow these groups in situ along typical reactions as the ageing. 

Apparently monochromatic resonance radiation of mercury which passes through mercury vapor at the saturated pressure at 25 °C is about half absorbed in four millimeters distance. Beer s law is not obeyed at all because the incident radiation cannot be considered to be actually monochromatic, and absorption coefficients of mercury vapor vary many times between zero and very high values in the very short space of one or two hundredths of an Angstrom unit. Moreover, absorption of mercury resonance radiation by mercury vapor is sufficiently great even at room temperature to make radiation imprisonment a very important phenomenon. If the reaction vessel has any dimension greater than a few millimeters the apparent mean life of Hg(63P ) may be several fold the true radiative life of 1.1 x 10"7 sec, reaction (27), because of multiple absorption and re-emission. 

The investigated CuPc in solution showed a good combination of a relatively high absorption cross section /c, a relatively high effective NL absorption coefficient /3eff> a very low energy-dependent saturation FsaU and a low linear absorption coefficient a0. The excellent combination of these values makes CuPc a very good candidate as an OL material [58]. 

The theory of the saturable absorption effect in single-wall carbon nanotubes has been elaborated. The kinetic equations for density matrix of n-electrons in a single-wall carbon nanotube have been formulated and solved analytically within the rotating wave approximation. The dependence of the carbon nanotube absorption coefficient on the driving field intensity has been shown to be different from the absorption coefficient behavior predicted forthe case of two level systems. 

The absorption coefficient (of solubility) a of a gas is the volume of gas reduced to 0 C and 1 atm. pressure which will be dissolved by unit volume of solvent at the experimental temperature under a partial pressure of the gas of 1 atm. Show that for a dilute solution, Ns in equation (36.23) may be replaced by a. The absorption coefficient of nitrogen is 0.01685 at 15" and 0.01256 at 35 C. Determine the mean differential heat of solution per mole of nitrogen in the saturated solution in this temperature range. 

Development of the W — fN H relation, the CoG, beyond the weak-line limit depends on the profile of the absorption coefficient <)>(AA). An extreme form for the profile is effective at illustrating this point. Suppose (AA) = a for AA = AXD and 0 for AA > AAj> Normalization of provides the relation connecting the constant a, the width AXd, and the /-value - the derivation is left as an exercise for the student With increasing fN H, I(AX)/Iq falls within the line to its minimum value of zero. At which point, the equivalent width has saturated at W = 2AAd- Note that, unlike W in the weak-line limit, the CoG beyond the weak-line portion depends on the shape of the line absorption coefficient - here, the width AAd. This dependence means that conversion of a measured W to JNlH for realistic absorption coefficient profiles demands observational or theoretical knowledge of the absorption coefficient s profile. This requirement plus the reduced sensitivity of W to /NlH make this part of the CoG less attractive for abundance determinations. This stretch of the CoG is variously referred to as the flat, Doppler or saturated part. 

For low intensities of probing radiation, the absorption coefficient is independent of intensity but for large intensities, the absorption decreases because of saturation effects (discussed later in the chapter). 

Figure 3. A log-log plot of the FACT) magnitude normalized to the coefficient K of Equation 2 vs. log B, where B = ft/as. ft is the optical absorption coefficient (cm 1) and a is the thermal conduction coefficients (cm 1). The onset of photoacoustic saturation occurs at logB = 0. B = ft/as as = 100 cm 1 ( 19).

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