Information transitions between electronic level

Ultraviolet-visible (UV) spectroscopy (Section 15.1) A type of spectroscopy that employs ultraviolet or visible light UV-visible spectroscopy uses transitions between electronic energy levels 10 provide information about the conjugated part of a compound. 

Every line in the hydrogen spectrum corresponds to a transition between electron energy levels. Spectral lines from hydrogen emission spectroscopy are shown at right and in the table below. Please see Skill 17.7 for additional information on atomic spectra. 

A characteristic feature of many d-block metal complexes is their colours, which arise because they absorb light in the visible region (see Figure 20.4). Studies of electronic spectra of metal complexes provide information about structure and bonding, although interpretation of the spectra is not always straightforward. Absorptions arise from transitions between electronic energy levels ... 

The spectroscopy of electron spin resonance (ESR) is a means of detecting direct transitions between electron Zeeman levels. The phenomenon of electron spin resonance is observed only in atomic or molecular systems having net electron spin angular momentum, that is, materials containing one or more unpaired electrons. One of the most useful parameters that can be extracted from ESR spectra is the spectral linewidth this parameter provides information on rotating correlation time (re)." ... 

Optical spectra of f ions and compounds are characterized by relatively sharp lines due to transitions between energy levels within the f configuration. From analyses of these types of spectra, information may be obtained about the interactions between the f electrons of the ion and their surrounding ligands. The parametric theory used to obtain... 

For solids and liquids, electronic absorption bands are usually broad and essentially featureless, but more information is obtainable from electronic spectra of gas-phase molecules. Transitions between two levels with long lifetimes are the most informative. Such an electronic transition for a gas-phase sample has various possible changes in vibrational and rotational quantum numbers associated with it, so that the spectrum, however it is obtained, consists of a number of vibration bands, each with rotational fine structure, together forming an electronic system of bands. The selection rules governing the changes in vibrational and rotational quantum numbers depend on the nature of the electronic transition, and they can be ascertained by analyzing the pattern and structures of the bands. 

More direct information can be obtained by the electron-spin resonance (paramagnetic resonance) method, in which the magnetic dipole transitions between the levels arising from the lowest states by the Zeeman splitting are observed as the resonance absorptions. This powerful method has been extensively applied to various paramagnetic salts, and the results are summarized in excellent review articles by the Oxford group. - - The reader is also referred to the recent interesting book by Low. ... 

Absorption in the ultraviolet and visible regions of the electromagnetic spectrum corresponds to transitions between electronic energy levels and provides useful analytical information for both inorganic and organic... 

The electron spin resonance spectrum of a free radical or coordination complex with one unpaired electron is the simplest of all forms of spectroscopy. The degeneracy of the electron spin states characterized by the quantum number, ms = 1/2, is lifted by the application of a magnetic field, and transitions between the spin levels are induced by radiation of the appropriate frequency (Figure 1.1). If unpaired electrons in radicals were indistinguishable from free electrons, the only information content of an ESR spectrum would be the integrated intensity, proportional to the radical concentration. Fortunately, an unpaired electron interacts with its environment, and the details of ESR spectra depend on the nature of those interactions. The arrow in Figure 1.1 shows the transitions induced by 0.315 cm-1 radiation. 

Electron spin resonance can provide detailed information about free radical (ions) in condensed media. Transitions between the electron spin levels are stimulated by radiation at frequencies satisfying the resonance condition ... 

As indicated before, the edge structure is sensitive to the chemical environment of the absorber. In the case of OsCu/Si02 catalysts, the magnitude of the Os Lm absorption threshold, which gives information on the electronic transition from the 2p3/2 core level to the vacant d states, is diminished by the presence of copper. This suggests an electronic interaction between Cu and Os in which the former contributes electrons to unfilled d states of the latter (266). 

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