Absorption spectra interpretation

Since the absorption spectrum is a ratio it is amenable to other interpretations. One such interpretation is that the absorption spectrum is the ratio of energy absorbed to energy incident. From this perspective, the quantity /)co(d/d0< li 0l f 0) is interpreted as the rate of energy absorption (per unit volume), since d E/d t = /)co(d AVd t) while tire quantity E dha is interpreted as the incident energy flux, which depends only on the field intensity and is independent of frequency. 

Figure Al.6.11. Idealized UV absorption spectrum of CO2. Note the regular progression of intemiediate resolution vibrational progression. In the frequency regime this structure is interpreted as a Franck-Condon...

The absorption and fluorescence spectra of a neat film made of RdB-den-drimer are shown in Fig. 2. The absorption spectrum in visible-wavelength region was similar to that obtained from a solution of RdB with a concentration less than 0.1 mmol/1. Interpretation of the fluorescence in terms of the Frank-Condon mechanism indicated that the core RdB chromophore behaved with a site-isolation effect and had little interaction with the neighboring chro-... 

Consider first blue sapphire Al203 Ti(III), Fe(III) (Fig. 2). In the absence of Fe(III) the absorption spectrum is easy to interpret. The weak band with a maximum at about 500 nm is due to the t2 —> e crystal-field transition on Ti(III) (3d ), the strong band at 2<280nm is due to a Ti(III)-0( — II) LMCT transition. The absorption band in the region around 700 nm in the case of the codoped crystal cannot be due to Fe(III). It has been ascribed to MMCT, i.e. to a transition within an iron-titanium pair ... 

Fluorescent probes are divided in two categories, i.e., intrinsic and extrinsic probes. Tryptophan is the most widely used intrinsic probe. The absorption spectrum, centered at 280 nm, displays two overlapping absorbance transitions. In contrast, the fluorescence emission spectrum is broad and is characterized by a large Stokes shift, which varies with the polarity of the environment. The fluorescence emission peak is at about 350 nm in water but the peak shifts to about 315 nm in nonpolar media, such as within the hydrophobic core of folded proteins. Vitamin A, located in milk fat globules, may be used as an intrinsic probe to follow, for example, the changes of triglyceride physical state as a function of temperature [20]. Extrinsic probes are used to characterize molecular events when intrinsic fluorophores are absent or are so numerous that the interpretation of the data becomes ambiguous. Extrinsic probes may also be used to obtain additional or complementary information from a specific macromolecular domain or from an oil water interface. 

Natural circular dichroism (optical activity). Although circular dichroism spectra are most difficult to interpret in terms of electronic structure and stereochemistry, they are so very sensitive to perturbations from the environment that they have provided useful ways of detecting changes in biopolymers and in complexes particularly those remote from the first co-ordination sphere of metal complexes, that are not readily apparent in the absorption spectrum (22). It is useful to distinguish between two origins of the rotational strength of absorption bands. 

The absorption spectrum of ehis intense, has a broad peak at about 720 nm (halfwidth -1 eV), and is structureless (see Sect. 6.1 and Figure 6.2). It covers at least 220 to 1000 nm and possibly extends on either side. There is some evidence that the absorption rises somewhat in the UV, which has been interpreted as the water absorption perturbed by the hydrated electron (Nielsen et al, 1969,1976). 

The ultrasonic absorption spectrum for a series of inorganic salts with /i-CD showed one relaxation process.166 No absorption was observed for solutions only containing /i-CD. The equilibrium constants determined from competitive binding isotherms were relatively low (2-30 M-1). The relaxation frequency (/, ) was related to the observed relaxation rate constant, which is equal to the sum of the association and dissociation processes. The association rate constants for all salts with the exception of perchlorate were similar and this result was interpreted to mean that... 

Note added in proof. Kamb, Hamilton, LaPloca and Prakash [J. Chem. Phys. 55, 1934 (1971)] have argued, from the comparison of the infrared absorption spectrum of HDO/H2O ice II and crystal structure data, that there is no correlation between vod and hydrogen bond donor angle. Instead, for this case they establish a correspondence between j>od and 00 separation. This interpretation differs from that offered by VRB for high density HaO(as). 

DR. GEOFFROY The 366 nm irradiations are clearly into the lowest absorption band. It is often a tail in these complexes. Unfortunately, the electronic structures of these compounds, as with most all organo-metallic systems, are not well-understood or well-defined. We could interpret the absorption spectrum in several different ways, and we could rationalize why we see hydrogen, depending on how we interpret the absorption spectrum. No matter what we do, we can rationalize hydrogen loss. But it is not very satisfying, because we do not know what the nature of the excited states is. That is an area which needs considerable study, to define the electronic structures of these kinds of compounds. 

The interpretation of these effects as the formation of a proton addition complex was further supported by Plattner et al. (1952) by means of spectroscopic and conductimetric investigations. In these interactions the change of the absorption spectrum is characteristic, since the blue colour of the azulene in organic solvents is changed to a yellow colour in... 

A third analysis of the UV absorption spectrum of borazine reported by Bernstein and Reilly is not in reement with Kaldor s assignments. Bernstein interprets the first vibrational progression in the same manner as Kaldor. However, for the second progression he reports a band at 2011 nm (not observed by Kaldor) which he interprets as a Vi hot band of aa" symmetry. He identifies the 197.5 nm origin of this band as the location of the Aj state. 

Vanadium(n) Complexes.—Dehydration of VSO. THjO has been shown to proceed via the formation of VS04,mH20 (where n = 6, 4, or 1) and V(OH)-(SO4), which were characterized by X-ray studies. The polarographic behaviour and the oxidation potential of the V -l,2-cyclohexanediamine-tetra-acetic acid complex, at pH 6—12, have been determined.Formation constants and electronic spectra have been reported for the [Vlphen),] " and [V20(phen)] complexes. The absorption spectrum of V ions doped in cadmium telluride has been presented and interpreted on a crystal-field model. The unpaired spin density in fluorine 2pit-orbitals of [VF ] , arising from covalent transfer and overlap with vanadium orbitals, has been determined by ENDOR spectroscopy and interpreted using a covalent model. " ... 

Kosbash What are the various interpretations for the difference between the rodless coneless physiology and the wild-type More generally, when I discussed these kinds of experiments with Aziz Sancar, he was always reminding me that the action spectrum on an animal is not the same as the action spectrum on a purified molecule. He was always critical of the facile interpretation of when you do an action spectrum with some behavioural output this defines the photopigment, in the same way that doing an absorption spectrum on a purified protein would. 

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