Decadic molar extinction coefficient

The quantity e is called the absorption coefficient or extinction coefficient, more completely the molar decadic absorption coefficient it is a characteristic of the substance and the wavelength and to a lesser extent the solvent and temperature. It is coimnon to take path length in centimetres and concentration in moles per... 

The oscillator strength is a temperature-independent intrinsic property of a molecule. The relation between the molar decadic extinction coefficient and the oscillator strength/can be expressed as follows ... 

P has a very suggestive form in relation to Figure 8.26. For a large concentration of acceptors, the second term in the denominator can be made considerably smaller than 1 (i.e., Xt is proportional to acceptor concentration [A]), and P will be independent of concentration. On the other hand, for a small concentration of acceptors, the second term in the denominator can be made considerably larger than 1, and P will fall off linearly as the concentration is reduced. The scale factor in all of this is Q. With Q large, the transition from concentration independence to linear concentration dependence will be at low acceptor concentrations. P falls to 5 when the second term in the denominator of Eq. (8.27) is equal to 1, and so a critical concentration of acceptors [A], /2 can be defined to characterize the falloff. Expressing Xt in terms of molecular parameters (x, = em[A] ln(10)/, where n is the particle refractive index, em is the molar decadic extinction coefficient, [A] is the concentration of acceptors, and k is 2n/X) yields... 

The spectra Fo(v) and Ca(v) are represented on the wavenumber scale and the fluorescence spectrum (F(v)) of the donor is normalized on this scale n is the refractive index, e iv) is the molar decadic extinction coefficient of the acceptor and To is the radiative lifetime (s) and R(nm) is the D-A center to center distant. For very strong coupling the rate is given by... 

Light Absorption by Chemical Species Molar Extinction Coefficients Illustrative Example 15.1 Determining Decadic Molar Extinction Coefficients of Organic Pollutants Chemical Structure and Light Absorption The Fate of Excited Chemical Species Quantum Yields... 

Determining Decadic Molar Extinction Coefficients of Organic Pollutants... 

Calculate the decadic molar extinction coefficients of nitrobenzene for the wavelengths indicated above. 

How is the decadic molar extinction coefficient, ,(/l), of a given compound defined What is described by the decadic light absorption or light attenuation coefficient,... 

Figure 1.5 Absorption spectrum of the hydrated electron the ordinate is the molar decadic extinction coefficient (m 1 cmr1)...

All upward radiative transitions in Figure 3.23 are absorptions which can promote a molecule from the ground state to an excited state, or from an excited state to a higher excited state. We have seen that the probability of these transitions is related ultimately to the transition moment between the two states and thereby to the Einstein coefficient A. In practice two other related quantities are used to define the intensity5 of an absorption, the oscillator strength f and the molar decadic extinction coefficient e. 

The absorption maxima in Figure 1, which shows the decadic molar extinction coefficient plotted against wavelength, are at 5800, 6300, 7000, 7400, and 8200 A. The determination of the maximum for methanol by Adams, et al. (1) is in close agreement with our value of 6300 A. that of Grossweiner, et. al. (17) for ethanol by flash photolysis is in satisfactory agreement with our value of 7000 A. It is immediately apparent that the maximum exhibits a red-shift with decrease in the static dielectric con-... 

Figure 1. The absorption spectra of the solvated electron in the aliphatic alcohols at 23°C. The ordinate gives the decadic molar extinction coefficient.

Table II. Summary of Molar Decadic Extinction Coefficients...

Liquid-Ammonia Solutions—Spectrum and Photolysis of Potassium Amide. Figure 6 shows the spectrum of a bleached solution of potassium in ammonia, at —48°C. Only a single peak due to the amide is seen at 335 m/z before the ammonia cutoff. The molar decadic extinction coefficient, as determined by titration, is e = (1.0 =fc 0.2) X 104 at —48 ° C. and 335 m/z. (A careful Beer s Law check on the 335 m/z band has not yet been made.) The temperature coefficient of the peak is —20 cm. 1 deg. 1 (3), which is close to the value given above for the longwave band in decomposed ethylamine solution. 

This law can also be given in decadic form, using the decadic molar extinction coefficient s ... 

The molar decadic absorption coefficient e is frequently called the extinction coefficient in published literature. Unfortunately numerical values of the extinction coefficient are often quoted without specifying units the absence of units usually means that the units are mol-1 dm3cm-1. See also [18]. The word extinction should properly be reserved for the sum of the effects of absorption, scattering, and luminescence. 

Extinction coefficient This term, equivalent to molar (decadic) absorption coefficient, is no longer recommended. 

Electronic Transitions. Since formaldehyde (H2C0) is the simplest carbonyl compound, the CO ir +- n electronic transition of the carbonyl compounds will be briefly described using the formaldehyde transition as the prototype. The lowest singlet state of the CO chromophore of an unconjugated carbonyl can be produced by one-photon absorption of light between 360 and 240 rim (46). This electronic transition is weak, with typical maximum decadic molar extinction coefficient (e) of less than 2 x 10 liters/mol cm. This transition corresponds to the well-known electric-dipole-forbidden vibronically allowed X A ... 

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