Absoiption line

The LOAS instrument consists of the following main units A tunable laser, a sample cell with an acoustic transducer (sometimes called a spec-trophone or SP), an amplifier, and a recording system. The acoustic response of the medium can be stimulated by amplitude or frequency modulation of the laser light or by Stark or Zeeman modulation of the absoiption line of the analyte. Both pulsed and cw lasers with mechanical or electro-optical amplitude modulation are often employed in LOAS analytical applications. 

Figure 4-5. lNDO/SCl-calculalcd transition energies of the lowest two optical transitions of a cofacial dimer formed by two slilhcnc molecules as a function of interchain distance. The horizontal line refers to the transition energy of the isolated molecule. Note that the upper value reported at 3.S A corresponds to the transition to the fifth excited stale, which provides the lowest intense absoiption feature. 

There is no sharp dividing line between pure physical absorption and absorption controlled by the rate of a chemiem reaction. Most cases fall in an intermediate range in which the rate of absoiption is limited both by the resistance to diffusion and by the finite velocity of the reaction. Even in these intermediate cases the equihbria between the various diffusing species involved in the reaction may affect the rate of absorption. 

Legend No number of measurement. Cone concentration in fig CN /100 ml Ab.sorb absorbance [AU] slope slope of regression line t CV intercept . see slope res. std. dev. residual standard deviation. res n number of points in regression LOD limit of detection LOQ limit of quantitation measurements using a 2-fold higher sample amount and 5-cin cuvettes—i.e., measured absoiption 0. .. 0.501 was divided... 

Figure 1. a) Absoiption (dotted line) and luminescence ( xc = 530 nm, solid line) spectra of amphi-PIC J-aggregates with DiD (amphi-PIC/DiD = 20 1). Dashed line — luminescence spectrum of amphi-PIC J-aggregates without DiD. b) Luminescence spectra of amphi-PIC J-aggiegates with traps at different trap concentration amphi-PIC/trap = 0 l, 1000 1, 500 1,200 1, 100 1,50 1,20 1, 10 1. 

Both atomic and molecular emission and absoiption can be measured when a sample is atomized in a flame. A typical flame-emission spectrum was shown in Figure 24-19. Atomic emissions in this spectrum are made up of narrow lines, such as that for sodium at about 330 nm, potassium at approximately 404 nm, and calcium at 423 nm. Atomic spectra are thus called line spectra. Also present are emission bands that result from excitation of molecular species such as MgOH, MgO, CaOH, and OH. Here, vibrational transitions superimposed on electronic transitions produce... 

Atomic absoiption spectroscopy (AAS) is probably still the most widely employed of all the atomic methods because of its simplicity, effectiveness and relatively low cost. A Tine source of radiation is required for AAS (they do not employ a continuous source of radiation) hence a complete spectrum is not obtained. The sources (which are changed depending on the element of interest) emit certain lines of radiation that have the same wavelength as that of the absorption peak of the analyte of interest. 

Fig. 1. Transient absorption spectra of the free and bound chromophores, at different pump-probe delays. Steady-state absoiption and fluorescence spectra are presented in dotted lines...

FIGURE 4.2. BL lamp axial radiative flux distiibiilion measured at two radial positions (A) 3.1-cm and (o) 4..S-cm. Solid lines represent the ESSDE model predictions evaluated at set radial positions (Reprinted from Chem. Eng. Joum., 90, M. Salaices, B. Serrano and H.I. de Lasa, Experimental evaluation of photon absoiption in an aqueous Ti02 sluiTy reactor, 219-229, Copyright 2002, with pemiission from Elsevier). 

The raw gas consists of an inert gas G, and of the absorptives. On the way up through the column, the absorptives are removed from the inert gas and, in turn, the amount of the gas phase decreases. Analogously, the amount of the liquid phase is increased during the absorption process. Therefore, the ratio of liquid to gas L/G changes and, in turn, the operating line becomes curved. This problem can be solved by using a concentration where the amounts of absoiptives are referred to the amount of pure inert gas and pure solvent, respectively ... 

Fig. 11.41 Absoiption specirum for ociahednil MnF. Note ihe narrow lines. [From Lever, A. B. P. Inorganic Etecironic Spectroscopy, 2nd ed. Elsevier New York. 1986 p4SI. Used with permission.]...

Figure 6-10. Effect of superficial liquid flow rate on height of transfer units for cartwn dioxide absoiption in water. Solid line data of Cooper etal. (1941) for 2- by 2- by 4e-ln. steel raschig rings. Dotted line tased on data of erwtxid and Htdlowi (1940) for 2-In. ceramic raschig rings...

Fig. 3. Silicate absoiption strength, calculated om the 9.8/un line-to-continuum ratio. The strongest attenuation occurs at IIlc2 (a foctor of 72 relative to the actjacent observed continuum) and is generally correlated with the source structure, suggesting that the extincting grains ate local to the individual sources. Crosses mark the positions of the sources om Figure 3, and is the position of the SiO maser and radio source P.

---