Absorption ABS

Gas absorption, as applied to the control of air pollution, is concerned with the removal of one or more pollutants from a contaminated gas stream by treatment with a liquid. The necessary condition is the solubility of these pollutants in the absorbing liquid. The rate of transfer of the soluble constituents from the gas to the liquid phase is determined by difflisional processes occurring on each side of the gas-liquid interface. 

Consider, for example, the process taking place when a mixture of air and sulfur dioxide is brought into contact with water. The SO2 is soluble in water, and those molecules that come into contact with the water surface dissolve fairly rapidly. However, the SO2 molecules are initially dispersed throughout the gas phase, and they can only reach the water surface by diffusing through the air, which is substantially insoluble in the water. When the SO2 at the water surface has dissolved, it is distributed throughout the water phase by a second difflisional process. Consequently, the rate of absorption is determined by the rates of diffusion in both the gas and liquid phases. 

Equilibrium is another extremely important factor to be considered in controlling the operation of absorption systems. The rate at which the pollutant will diffuse into an absorbent liquid will depend on the departure from equilibrium that is maintained. The rate at which equilibrium is established is then essentially dependent on the rate of diffusion of the pollutant through the nonabsorbed gas and through the absorbing liquid. Equilibrium concepts and relationships are considered in a later problem. 

The rate at which the pollutant mass is transferred from one phase to another depends also on a so-called mass transfer, or rate, coefficient, which equates the quantity of mass being transferred with the driving force. As can be expected, this transfer process would cease upon the attainment of equilibrium. 

Gas absorption can be viewed as a mass transfer, or diffusional operation, characterized by a transfer of one substance through another, usually on a molecular scale. The mass transfer process may be considered the result of a concentration 

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Figure 9-12. Absorption (Abs), photoluminescence excitation spectrum (PLCX), pholo-lumincscence (PL), and electroluminescence (EL) emission of mLPPP.

Fluorescence and Phosphorescence. Fluorescence spectra using the diode array linear imaging apparatus were obtained for GAV in benzene and in isopropanol at ambient temperatures. The fluorescence and absorption spectra are characterized by absorption (abs) =280 nm and 230 nm, and a A (emission) = 368 nm in... 

For optical ET, the vertical gaps for Franck-Condon maxima hv)max) in absorption (abs) and emission (em) are given by [29,42 14]... 

Figure 26 Emission spectra (PL, EL) in PC at room temperature of 40 wt% TPD donor solution with a 40 wt% of PBD acceptor added. The photoluminescence (PL) spectrum excited at 360 nm, the electroluminescence (EL) spectra (I, II) originate from the recombination radiation in a 60 nm thick film, taken at two different voltages. Absorption (Abs) and PL spectra (excitation at 360 nm) of (75wt% TPD 25wt% PC) and (75wt% PBD 25wt% PC) spin-cast films are given for comparison. Molecular structures of the compounds used are given in the upper part of the figure TPD [N,Nf-diphenyl-A v/V/-bis(3-methylphenyl)-l,l -biphenyl-4,4 diamine PBD [2-(4-biphenyl)-5-(4- er .-butylphenyl)l,3,4-oxadiazole PC[bisphe-nol-A-polycarbonate]. Adapted from Ref. 112.

Figure 15-31. (a) CIS/cc-pVDZ energies of m-DMABN as a function of CCN angle, (b) Steady-state absorption (ABS) and local emission (LE) spectra of m-DMABN in acetonitrile at room temperature, (c) fs-transient absorption spectra of m-DMABN in acetonitrile... 

With more than one species involved, the absorption (Abs) has to be summed over all molecular species each weighted by their relative concentrations, (sp) (equation 11). 

Figure 9 Absorption (abs.) and emission (em.) widths obtained by changing the static solvent dielectric constant in the range = 3 - 65 versus the Stokes shift Cco = 2.0. The dash-dotted line indicates the equality hAv = Pa is valid for Ao(o = 0.

Figure 17 The normalized absorption (abs.) and emission (em.) intensities at Ae = 0.7 (solid lines) and Ae = 0.8 (long-dashed lines) versus the reduced frequency hv/X ...

Figure 20 Absorption (abs.) and emission (em.) solvent-induced FCWD of C153 in acetonitrile calculated according to the APM model (solid lines), the TSM (dash-dotted lines), and the polarizable model (Eq. [153], dashed lines).

Figure 7 Electronic absorption (Abs), magnetic circular dichroism (MCD), and circular dichroism (CD) spectra of mouse Cd7-MT-1 in 25 mM Tris/HCl, SOmMNaCl, pH 8.0. (Reproduced by permission of the American Society for Biochemistry Molecular Biology)...

Figure 8 Electronic absorption (Abs), circular dichroism (CD) and luminescence (Lum) spectra, at 77 K and excitation at 300 nm, of...

Figure 4.3 shows the photo-orientation, i.e., the dichroism, observed in the azo-silane SAMs. These spectra were obtained after 3 minutes of irradiation with linearly polarized UV light. It is clear that the absorption, Absx, recorded with the probe light linearly polarized perpendicular to the initial UV-light polarization, is higher than the absorption, Abs//, recorded with the probe light linearly polarized parallel to the initial UV-light polarization. Identical spectra were recorded for both Abs// and Absx prior to UV irradiation (only... 

Fig. 4. Normalized absorption (ab) and fluorescence (fl) spectra of films containing C481 and TSPP. Flourescence spectra are obtained at the bofli flie right angle (RA) and front face (FF) collection geometry using an excitation wavelength of 400 nm.

When a compound is administered by a route other than intravenously, the plasma level profile will be different as there will be an absorption phase, and so the profile will be a composite picture of absorption in addition to distribution and elimination (figure 3,26). Just as first-order elimination is defined by a rate constant, so also is absorption, ab. This can be determined from the profile by the... 

Table 2-4. Types of Primary Photochemical Processes Following the Act of Photon Absorption AB + he - AB ...

Fig. 1.1. Electronic and vibrational energy levels (schematic, rotational are omitted for simplicity), So singlet ground state, Sj excited singlet state (higher electronically excited states are omitted in this figure), T triplet electronically excited energy state. Straight lines symbolise radiative processes (absorption (Ab) as well as emission F, fluorescence P, phosphorescence). Wavy lines give the radiationless transitions, ic, internal conversion isc, intersystem crossing sd, radiationless deactivation te, thermal equilibration.

Figure 13.23. (a) Fluorescence (F) and absorption (Abs) or fluorescence excitation (FE) spectra of ailT thin films on quartz glass. Excitation in the maximum of absorption band A. angle of incidence 60°. 

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