Absorption contour

Taken together these two mechanisms are considerably more effective than either one alone both require broad bands made up of a number of sub-bands. A number of possible explanations can be advanced for the common blurring together of such sub-bands to give smooth absorption contours which of these is operative may depend on the specific case. 

It is obvious that the absorbed energy in a given frequency region will have a finite value only if the emission and absorption contours have finite values in this region. For example, the conditions represented in Figure II would correspond to the. requirements for excitation of a single isotopic species, whereas in Figure 4, both mono- and di-isotopic excitations are indicated. 

In practice this condition may be fulfilled not only in excitation, e.g. by means of a pulsed laser or a continuous dye laser with insufficient frequency selectivity, but also by means of fines from a continuous gas laser working in simultaneous axial mode u>i (multimode) generation regime see Fig. 3.10(a). Let Au>i = u>i+1 — uii = itc/L denote the mode separation in a laser, L being the resonator length. Then, as pointed out in [110, 127, 231], broad line approximation works if Awj is smaller than the width of the Bennet holes r en [268, 320] in the absorption contour see Fig. 3.10(6). The positions of the Bennet holes are determined by the condition ujq — w/ + kv = 0, where luq is the central transition frequency, k is the wave vector and v is the velocity of the absorbing particle. The broad fine approximation is valid if the following conditions are fulfilled (see Fig. 3.10) ... 

We wish to add that there exists a wide variety of literature that considers the opposite case of monochromatic excitation by an infinitely narrow line causing velocity selection, such as [261, 268, 269, 320, 362] and the sources quoted therein. This description has been developed basically in connection with laser theory it refers most often to stabilized single-mode excitation. The intermediate case between monochromatic and broad line excitation is the most complex one, requiring integration over the modal structure of the laser inside the bounds of the absorption contour [28, 231, 243]. 

Fig. 9. The computed absorption contour of the 0—0 band of the 2 L4i. 3000 A system of phenanthrene...

Figure 7 Calculated absorption contours at 298 K for different values of A and Xn. (Reprinted with permission from Ref 20. 1988 American Chemical Society)...

The above mechanism suggests that the unknown product(s) is nitrosohydrazine and/or nitrohydrazine. The position of the unknown IR absorption at -988 cm" is not inconsistent with the expected N-N stretching frequency for these compounds. However, the positions and contours of other weaker absorptions, which... 

FIGURE 7.3 Kubelka-Munk contour plot of a spinach leaf extract, taken at 305 nm. The two signals at 16- and 17-mm distances are due to chlorophyll b and chlorophyll a, which show absorptions beyond 550 nm. 

If microstates lead to the existence of a distribution of energies of interaction between aromatic groups and neighboring groups of atoms, then the individual spectra of these groups in different microstates shift differently, which results in an inhomogeneous contour of the absorption band. The application of selective photoexcitation permits specific effects of the distribution of microstates on spectral, temporal, and polarization fluorescence properties to be observed. 221 Such effects have been observed in studies of proteins, 1,8) and, as we show below, they may be used to obtain important information on dynamics. 

Figure 3. Contour plot of 500 MHz pure absorption NOESY spectrum of globoside at 303 K. The labeled cross peaks correspond to the interresidue and intraresidue connectivities for globoside. (Reproduced from ref. 40. Copyright 1986 American Chemical Society.)...

For UV spectra of parent and substituted 1,2,3-triazoles and benzotriazoles, see CHEC-I <84CHEC-1(5)684 >. The UV spectra of benzotriazole, 1-methyl- and 2-methyl-benzotriazole in the gas phase at 90°C have been recorded <94JOC2799>. 1-Alkyltriazolines show two A ax in acetonitrile, 239-242 and 263-266 nm, both with log e w 3.50 <93JOC2097>. The UV spectra of bicyclic triazolines (754) have been recorded <9lJOC4463>. The Si-So electronic absorption spectrum of 1/f-benzotriazole at 286 nm has been studied by computer simulation of the rotational contours. The result shows that the benzotriazole band is an almost pure type-5 band <93JSP(158)399>. 

More insight into shape effects in absorption spectra of small particles can be acquired from contour plots in the complex c plane lines of constant dimensionless cross section 3(Cabs)/kt> are shown in Fig. 12.9a, b, c. Note that the curves are symmetric about the lines c = — 2, c = - 1, and e = 0 for the sphere, needle, and disk, respectively. Three points representing certain solids... 

Differences in surface plasmon absorption among various metals are clearly revealed by imagining the trajectories to be superposed onto the contour plot . Spherical silver and aluminum particles have intense surface plasmon absorption peaks because t" is small at the frequency where c is - 2, whereas gold... 

The SCF-A a-SW calculation also confirms the importance of the back donation component of this model, and a contour plot of the relevant molecular orbital is shown in Fig. 3. Johnson and his co-workers (193) have estimated that this component may contribute up to 25% of the total metal-olefin bond energy. These calculations have given a more satisfactory account of the electronic absorption characteristics of this... 

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