Absorption band splitting

Interaction of two chromophores exhibiting allowed (strong) n-n absorption bands splits the excited state into two energy levels with the energy gap 2VSj (Davydov splitting), Figure 12. 

Let us now consider the retarding action of proteolytic enzymes on hydrolysis. Attention should be drawn to the fact that the carbonyl absorption band splits into two parts as a result of interaction of the cured KL-3 with proteolytic enzymes and kidney extract. Evidently it is associated with the specific interaction of the enzyme and urethane group in the polymer, the structure of which resembles the peptide group of a protein molecule. Owing to the specific action of the enzyme, this interaction does not accelerate the hydrolysis of urethane groups but even retards it owing to the shielding effect of the enzyme protein molecule. 

The electronic absorption spectrum of metal nanocrystals in the visible region is dominated by the plasmon band. This absorption is due to the collective excitation of the itinerant electron gas on the particle surface and is characteristic of a nanocrystal of a given size. In metal colloids, surface plasmon excitations impart characteristic colors to the metal sols, the beautiful wine-red color of gold sols being well-known [6-8]. The dependence of the plasmon peak on the dielectric constant of the surrounding medium and the diameter of the nanocrystal was predicted theoretically by Mie and others at the turn of the last century [9-12]. The dependence of the absorption band of thiol-capped Au nanocrystals on solvent refractive index was recently verified by Templeton et al. [13]. Link et al. found that the absorption band splits into longitudinal and transverse bands in Au nanorods [6, 7]. 

Fig. 13 Isotopic line splitting of the V3 stretching vibration in single crystalline (see also Fig. 12(a)), after [108, 109], The origin of each absorption band is indicated by an isotopomer present in crystals of natural composition. While the absorption could be fitted by a Lorentzian band profile, the remaining peaks were dominated by the Gaussian contribution in the Voigt band shapes (solid lines below the spectrum). The sum result of fitting the isotopic absorption bands is inserted in the measured spectrum as a solid line...

Further dehydration of boehmite at 600 0 produces y-alumina, whose spectrum is shown in Figure 3b. There is a loss in surface area in going from boehmite to y-alumina. The sample shown here has a surface area of 234 m /g (this sample was obtained from Harshaw A23945 the calcined Kaiser substrate gave an identical infrared spectrum). The y-alumina sample shows two major differences from o-alumina. First, there is a more intense broad absorption band at 3400 cm" due to adsorbed water on the y-alumina. Second, the y-alumina does not show splitting of the phonon bands between 400 and 500 cm" as was observed for o-alumina. The y-alumina is a more amorphous structure and has much smaller crystallites so the phonon band is broader. The y-alumina also shows three features at 1648, 1516 and 1392 cm" due to adsorbed water and carbonate. 

At first glance, the three fold splitting of the 2P-2S absorption band of Cu in Ar, Kr and Xe matrices might lead one to... 

Simple 1,2,3-thiadiazoles show three absorption bands in the ultraviolet (UV) 211-217 (emax 4380-5300), 249-253 (1460-2100), 290-294 (195-245) nm <1996CHEC-II(4)289>. The ESR spectrum for the radical anion generated by the electrochemical reduction of the 1,2,3-thiadiazolium ion 8 has been reported. A number of 5-substituted derivatives were also examined and the splitting constants in the ESR spectrum were analyzed <1998MRC8>. 

These structural data demonstrate that 12 is a rather less distorted molecule than [2.2]paracyclophane. However, a dramatic effect of the strong cr(Si—Si)—w interaction was observed in UV spectra as shown in Fig. 5. In the UV spectrum of phenylpentamethyldisilane, an intramolecular crfSi—Si)—7T charge-transfer band appears around 231 nm (11a, 12). Octamethyltetrasila[2.2]ortho- (15) and metacyclophane (16) show similar absorptions, but the band splits into two bands at 223 nm (e = 19,100) and 263 nm (e = 22,500) in 12. This type of red shift in the UV spectra occurs only in 12 among other polysilapara-cyclophanes such as 13 and 14. 

The absorption characteristics of PS I were measured on the four kinds of subphase surfaces during compression. As an example, Figure 2 shows the absorption spectra of the PS I monolayers on the PBV subphase surface under different surface pressures. Two absorption bands at about 420-450 and 676 nm increase with the compression, indicating the accumulation of the PS I to form a condensed monolayer. Compared to the absorption spectrum of PS I in solution (Fig. 3), the band at around 436 nm splits into two peaks. The wave-shaped small band between 470 and 630 nm is due to a low single-to-noise ratio on the water surface. These spectral features together with the jt-A isotherms indicate that PS I remains at the interface, and that the loss of PS I, due to dissolving into the subphase, is not significant [2],... 

Absorption bands arising from adjacent protons are split into multiplet peaks by a mutual interaction of the spins. The effect is due to small variations in the effective field experienced by a proton when neighbouring nuclei can occupy two or more energy levels or spin states. It is transmitted through the intervening bonds by a tendency for electron and nuclear spins to be paired. 

Consider the case of two single (methine) protons HA and Hx attached to adjacent carbon atoms and with quite different chemical shifts (Figure 9.32(a)). The field experienced by HA is increased or decreased slightly by the two allowed spin states of Hx, designated and l, and which in the gross sample are virtually equally populated. This results in the absorption band for HA splitting into a doublet whose peak intensities are in the ratio 1 1. The effect is mutual in that the two almost equally populated spin states of HA cause the Hx absorption to split into an identical doublet. The spacing... 

The estimation of the crystallinity index (Cl) of bone is based on one of the four vibrational modes associated with the apatite phosphate group. In amorphous calcium phosphate, the absorption band at 550-600 cm-1 appears as a single broad peak, whilst in hydroxyapatite it is split into bands of unequal intensity by the apatite crystal field (Sillen and Parkington 1996). Based on the splitting factor introduced by Termine and Posner (1966), Weiner and Bar-Yosef (1990) proposed the use of a crystallinity index to measure the crystallinity of bone mineral. As illustrated in Fig. 4.7, the Cl is estimated by drawing a base line from 750 to 495 cm 1 and measuring the heights of the absorption peaks at 603 cm-1 (measurement a), 565 cm 1 (measurement b) and the distance from the base line to the lowest point between the two peaks (c). Cl is calculated from the formula ... 

Type 1 Cu(II) intense (e > 3000 M 1 cm ) blue (2max 600 nm) optical absorption band EPR spectrum with an uncommonly small hyperfine splitting in gn region. 

The intriguing properties of devices made by the combination of a film-forming dye and an optical microstructure turn up in the discovery of strong coupling between excited states and photon modes in microcavities, creating Rabi-splitted polariton modes [211]. They occur in materials with narrow absorption bands (e.g., porphyrins and cyanine dyes) and may pave the way to new laser types and fundamental insights into the interaction of matter and light. 

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