Absorption spectra containing

The infrared absorption spectra contained in this section are provided in conjunction with the requirements for Identification as specified for a number of substances in this edition... 

In lanthanide compounds such as LnBr3 the absorption spectra contain bands in the charge transfer region involving electron transfer from ligand to metal. From energies of electron transfer bands it is possible to relate the redox potential with the electron transfer bands. This type of relationship leads to ,°[Tm3+/Tm2+] = —2.5 V, E[Pr4+/Pr3+] =... 

The UV absorption spectra contain a third band with maximum at about 6.0 eV [104,111]. The calculations assign this band to the third state of symmetry, which is computed to have a 0-0 transition energy of 5.53 eV, which increases to 5.79 eV at the twisted geometry. The UV absorption spectra have been recorded in solution and direct comparison is therefore not possible, since the ground-state conformation of the molecule is not known. It is probable that it is cis, at least in polar solvents. But the assignment of the band is clear. A fourth state has actually been calculated with an adiabatic energy of 6.02 eV (not included in Table VIII). The band at 6eV is probably composed of both these transitions. The computed intensity for the latter state is, however, small. 

The standard red-ox potential of tellurium in alkali chloride melts is more positive than that of palladium. Addition of elemental tellurium to NaCl-CsCl-U02Cl2 melt at 550 °C resulted in a quite slow uranium reduction reaction. After 180 min the oxidation state of uranium decreased to 5.92 and the concentration of uranium in the melt from 0.85 to 0.79 wt%. The absorption spectra contained two well pronounced bands corresponding to the uranyl(V) complex, U02Cl4 . 

EXAFS is part of the field of X-ray absorption spectroscopy (XAS), in which a number of acronyms abound. An X-ray absorption spectrum contains EXAFS data as well as the X-ray absorption near-edge structure, XANES (alternatively called the near-edge X-ray absorption fine structure, NEXAFS). The combination of XANES (NEXAFS) and EXAFS is commonly referred to as X-ray absorption fine structure, or XAFS. In applications of EXAFS to surface science, the acronym SEXAFS, for surface-EXAFS, is used. The principles and analysis of EXAFS and SEXAFS are the same. See the article following this one for a discussion of SEXAFS and NEXAFS. 

The absorption spectrum contains fine-structure details in the vicinity of this X-edge. The general subject has been reviewed by Compton and Allison (S), by Sandstrom (3), and by Tomboulian (4)- The review presented here will be brief. 

The spectrum obtained for the soluble residue from the chloride mixture gave no evidence of die presence of pyridinium chloride. However, the residue from the bromide mixture gave an infrared absorption spectrum containing 11 of the 14 bands observed in the known sample of pyridinium bromide, including a characteristic, very broad band between 2300 and 2800 cm.-1 Thus there was evidence that pyridinium bromide was a constituent of the reaction mixture ob-... 

T. Urbanski and Witanowski [109] found that the infra-red absorption spectrum contains the bands ... 

Figure 36. Portion of the NjO-HBr absorption spectrum containing a prominent Q-branch. The etalon trace was taken simultaneously with the N20-HBr spectrum. This spectrum reflects the broadside nature of the complex. Note the change in the horizontal scale relative to Figure 35.

Reduction of the orange-red solution of thebaine in concentrated hydrochloric acid with zinc affords a yellow phenolic base about which little is yet known beyond the facts that it is dimolecular and contains no carbonyl group. Its ultra-violet absorption spectrum contains a band at about 3,800 A, apparently indicating the presence of a highly conjugated system of double bonds such as... 

If the absorption spectrum contains only one line which is narrow, on either side of this line the function I approaches J0, and the two become practically identical at X2 and Xi if these limits are chosen sufficiently greater and smaller, respectively, than Xo the center of the line. At these limits the derivatives of the two functions will also become equal. Consequently all of the right-hand member of equation (3) vanishes, except as given in the following equation... 

Emission spectra axe usually much more complicated than Direct Absorption spectra, because an absorption spectrum contains all possible upward transitions from a single initial vibration-electronic state, typically the ground state, whereas an emission spectrum contains all possible downward transitions from... 

The oxy form of these O2-binding dinuclear copper centers is characterized by a number of distinct spectroscopic signatures. The electronic absorption spectrum contains two intense charge transfer bands in the visible region, at 350 nm (e 20 000 cm ) and 570nm (e 1000M cm ). ... 

The absorption spectrum containing many bands with partially overlapped contours is typical for the majority of materials [4], The magnitudes of damping of the corresponding IR-active modes can be determined by nonlinear energy transfer processes from the given vibration to other vibrations. The formulas for the dielectric functions in the case of coupled modes were obtained by Barker and Hopfield [85]. The interaction of a (discrete) phonon with a continuous electronic excitation can result in specific band distortions [86] named the Fano resonances. 

Recent experimental studies on benzene have shown that the absorption spectrum contains local mode features, that is, evidence of local isolated bond motions. In the benzene case, the C—H bonds, if they contain sufficient energy, appear directly in the spectrum, as if they were decoupled from the remainder of the molecular framework. In particular, one sees evidence of excitation to the overtones of C—H stretch, that is, five, six, seven, etc. quanta of energy in the bond. The experimental results further indicate that if energy is deposited in these bonds, it would transfer to the remainder of the benzene nuclear framework within about 10 sec. Although apparently rapid, this rate of energy transfer is substantially slower than that expected from a C—H bond democratically linked to all the degrees of freedom in the ring. 

Unfortunately, addition of copper(II)nitrate to a solution of 4.42 in water did not result in the formation of a significant amount of complex, judging from the unchanged UV-vis absorption spectrum. Also after addition of Yb(OTf)3 or Eu(N03)3 no indications for coordination were observed. Apparently, formation of a six-membered chelate ring containing an amine and a ketone functionality is not feasible for these metal ions. Note that 4.13 features a similar arrangement and in aqueous solutions, likewise, does not coordinate significantly to all the Lewis acids that have been... 

Diphenylhydrazine (hydrazobenzene) [122-66-7] M 184.2, m 34°, 44°, 175°/10mm, 222°/40mm, pKe i -1.7. Crystd from hot EtOH containing a little ammonium sulfide or H2SO3 (to prevent atmospheric oxidation), preferably under nitrogen. Dried in a vacuum desiccator. Also crystd from pet ether (b 60-100°) to constant absorption spectrum. HCl, from EtOH has m 163-164°(dec). Picrate, from C6H6, has m 123°(dec). 

RAIRS spectra contain absorption band structures related to electronic transitions and vibrations of the bulk, the surface, or adsorbed molecules. In reflectance spectroscopy the ahsorhance is usually determined hy calculating -log(Rs/Ro), where Rs represents the reflectance from the adsorhate-covered substrate and Rq is the reflectance from the bare substrate. For thin films with strong dipole oscillators, the Berre-man effect, which can lead to an additional feature in the reflectance spectrum, must also be considered (Sect. 4.9 Ellipsometry). The frequencies, intensities, full widths at half maximum, and band line-shapes in the absorption spectrum yield information about adsorption states, chemical environment, ordering effects, and vibrational coupling. 

Worenine. This alkaloid, also obtained by Kitasato from Coptis japonica was isolated as the tetrahydro-base, C,oHjg04N, which crystallises from alcohol in colourless prisms, m.p. 212-3°, and is oxidised by iodine in alcohol to worenine iodide, yellow crystals from which worenine chloride, thin orange-yellow prisms, m.p. 295° (dec.), can be obtained. Tetrahydro-worenine behaves as a tertiary base, contains methylenedioxy- but no methoxyl groups, and its absorption spectrum closely resembles that of tetrahydrocoptisine from which it differs in empirical composition by. CHj. Worenine is, therefore, represented by (XXX), the alternative position (a) for the methyl group being untenable, since a-methyltetra-hydrocoptisine obtained by Freund s method is not identical with... 

The preceding empirical measures have taken chemical reactions as model processes. Now we consider a different class of model process, namely, a transition from one energy level to another within a molecule. The various forms of spectroscopy allow us to observe these transitions thus, electronic transitions give rise to ultraviolet—visible absorption spectra and fluorescence spectra. Because of solute-solvent interactions, the electronic energy levels of a solute are influenced by the solvent in which it is dissolved therefore, the absorption and fluorescence spectra contain information about the solute-solvent interactions. A change in electronic absorption spectrum caused by a change in the solvent is called solvatochromism. 

Like acridine, phenanthridine and dimethyl acetylenedicarboxylate in methanol give a high yield of 1 1 1 molar adduct. Ultraviolet absorption spectrum comparisons show that this is best formulated as 9,10-dihydro-9-methoxy-10- (tran.s-l,2-dimethoxycarbonylvinyl) phenanthridine (142) rather than the corresponding phenanthridinium methoxide (143) under neutral conditions acidification changes the spectrum to that characteristic of the phenanthridinium cation. Crystallization of the adduct (142) from methanol containing 5-15% of water gave the betaine [(144) the positions of the ester and carboxylate groups have not been established], while in the presence... 

As yet no quinazoline has been discovered which has any appreciable amount (say, 1%) of hydrated species in the neutral molecule,but several quinazolines were shown to contain a mixture of anhydrous and hydrated species in the cations. Anhydrous neutral molecules and anhydrous cations have an ultraviolet absorption spectrum of the general type C (Fig. 3) and hydrated cations, the type... 

When an ionic solution contains neutral molecules, their presence may be inferred from the osmotic and thermodynamic properties of the solution. In addition there are two important effects that disclose the presence of neutral molecules (1) in many cases the absorption spectrum for visible or ultraviolet light is different for a neutral molecule in solution and for the ions into which it dissociates (2) historically, it has been mainly the electrical conductivity of solutions that has been studied to elucidate the relation between weak and strong electrolytes. For each ionic solution the conductivity problem may be stated as follows in this solution is it true that at any moment every ion responds to the applied field as a free ion, or must we say that a certain fraction of the solute fails to respond to the field as free ions, either because it consists of neutral undissociated molecules, or for some other reason ... 

From the color (absorption spectrum) of a complex ion, it is sometimes possible to deduce the value of AOJ the crystal field splitting energy. The situation is particularly simple in 22Ti3+, which contains only one 3d electron. Consider, for example, the Ti(H20)63+ ion, which has an intense purple color. This ion absorbs at 510 nm, in the green region. The... 

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