Resonance, absorption

Laser Photochemistry. Photochemical appHcations of lasers generally employ tunable lasers which can be tuned to a specific absorption resonance of an atom or molecule (see Photochemical technology). Examples include the tunable dye laser in the ultraviolet, visible, and near-infrared portions of the spectmm the titanium-doped sapphire, Tfsapphire, laser in the visible and near infrared optical parametric oscillators in the visible and infrared and Line-tunable carbon dioxide lasers, which can be tuned with a wavelength-selective element to any of a large number of closely spaced lines in the infrared near 10 ]lni. 

Hu, Y., Heshimoto, H., Moie, G., Hengartner, U., and Koyama, Y. 1997. Unique properties of the ll-cis and 11,11 -di-civ isomers of P-carotene as revealed by electronic absorption, resonance Raman and 1H and 13C NMR spectroscopy and by HPLC analysis of their thermal isomerization. J. Chem. Soc. Perkin Trans. 2 2699-2710. 

H. Intracluster Reactions Initiated through Photon Absorption Resonant Enhanced Ionization... 

Absorption resonances resulting from excitation of surface modes are accompanied by scattering resonances at approximately the same frequencies this was pointed out following (12.26). In most experiments transmission is measured to determine extinction, which is nearly equal to absorption for sufficiently small particles. However, surface mode resonances have been observed in spectra of light scattered at 90° by very small particles of silver, copper, and gold produced by nucleation of vapor in an inert gas stream (Eversole and Broida, 1977). The scattering resonance peak was at 3670 A, near the expected position of the Frohlich mode, for the smallest silver particles. Although peak positions were predictable, differences in widths and shapes of the bands were concluded to be the result of nonsphericity. 

M. Chergui My question to Prof. Gerber relates to the lifetime of the absorption resonance at 510 nm in Nan clusters. 

The measured x value for poly(methylphenylsilane)(PMPhS) at 1.064 nm is significantly larger than at 1.097 tm due to the absorption resonance of the third harmonic. A similar conclusion has recently been reported by Morichere et al. 

Although the list of applicable species is limited, most are of extreme interest in combustion research. The fluorescence signals will be independent of gas quenching effects if the absorption resonances can be saturated. Two level models, when properly interpreted, are applicable to data reduction, but rotational relaxation/coupling effects need to be quantitatively evaluated. More fundamental research investigations are required to address these questions for this potential to be realized. 

Since the transitions involved in gamma absorption resonance are quantum transitions, the quadrupole splitting of the nucleus can be described as follows [143] ... 

Fig. 1. On the left is a simplified energy-level diagram for l Hg+. The 281.5 nm quadrupole "clock" transition can be observed by monitoring the 194 nm fluorescence. If the ion has made a transition from the Si to the 5/2 level the 194 nm flourescence disappears. For the figure on the right, on the horizontal axis is plotted the relative detuning from line center in frequency units at 281.5 nm. On the vertical axis is plotted the probability that the fluorescence from the 6s Si - 6p pi first resonance transition, excited by laser radiation at 194 nm, is on immediately after the 281.5 nm pulse. The electric-quadrupole-allowed S-D transition and the first-resonance S-P transition are probed sequentially in order to avoid light shifts and broadening of the narrow S-D transition. The recoilless absorption resonance or carrier (central feature) can provide a reference for an optical frequency standard. (From ref. 11)...

The absorption is observed at the poles of t, at the energy oj, shifted relative to coB (4.101) by the local field. If a>, is close to an excitonic transition of the host crystal, the absorption resonates strongly for to/ tuke in fact, the impurity transition is polarized according to the host excitonic transition in its vicinity.16 (In other words, the impurity borrows oscillator strength, and more or less spatial extension, from the host band.184... 

Horsley (126,127a) has put the relation proposed by Lytle et al. on a more reliable quantitative basis by using accurate calculations of the unoccupied d orbital state using the X4-SW method rather than semiempirical estimates. Using simple deconvolution of the absorption-edge resonance, a relationship has been established between the total vacant d orbital states for a series of platinum compounds and the (corrected) combined areas of the Lu and Lni absorption resonances, rather than the area of the L ii resonance alone, as earlier proposed. This is justified since the LH threshold resonance line arises from transitions from the 2plj2 core level to empty d states of d3/2 character, and the Lm resonance line arises from transitions from the 2p3l2 core level to empty d states of d5/2 character. 

Figure 4 (a) Low-resolution scanning transmission electron microscopy (STEM) image of a thin sol-gel film (1 -2 layers) containing 5 nm CdSe NCs. The NCs appear in white, and the dark areas are pores, (h) Linear absorption (solid line) and PL (dashed line) spectra of as-prepared CdSe NCs (r = 2.5 nm) in a hexane solution (the arrow marks the lowest IS absorption resonance), (c) Absorption and PL spectra of the same NCs after their incorporation into titania... 

By pumping the Tryptophan-Ag colloid with 800nm, the excitation of the Tryptophan molecule is assisted by silver particles two-photon absorption. Resonant absorption of two-photon by the NPs is related to the imaginary part of the effective... 

The respective redox potentials of the first and second reduction step in THF [18, 21] are -2.68 and -3.31 V. The corresponding values in DMF [101] are -2.57 and -3.13 V. [All redox potentials in this chapter are reported relative to the ferro-cenelferricinium couple.) Both reduced forms of bpy are intrinsically stable in strictly aprotic and anaerobic media. For bpy and some other polypyridines, the radical anions and/or dianions have been characterized by UV-Vis absorption, resonance Raman, and/or EPR spectroscopy [18, 21, 70, 71, 102, 103]. Bipyridine derivatives with strongly electron-accepting groups -C(0)OEt or -Ph in 4,4 positions have a third reduction step at very negative potentials [18, 21]. Free phen [104] and tpy [101] are reduced by one electron at potentials similar to that of the first bpy reduction. The second reduction steps of phen and tpy are chemically irreversible. 

Mossbauer effect. A nuclear phenomenon discovered in 1957. Defined as the elastic (recoil-free) emission of a 7-particle by the nucleus of a radioactive isotope and the subsequent absorption (resonance scattering) of the particle by another atomic nucleus. Occurs in crystalline solids and glasses but not in liquids. Examples of y-emitting isotopes are iron-57, nickel-61, zinc-67, tin-119. The Mossbauer effect is used to obtain information on isomer shift, on vibrational properties and atomic motions in a sohd, and on location of atoms within a complex molecule. 

In the X-ray anomalous scattering method we make use of the fact that the scattering length of an element changes appreciably near an absorption resonance and is given by ... 

Figure 4.18 The effect of copper on the threshold X-ray absorption resonance associated with the absorption edge of the osmium in a silica-supported catalyst (32). (Reprinted with permission from the American Institute of Physics.)...

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