Structure of electronically excited

In order to discuss the geometrical structures of electronically excited states, the same procedure as described above is used, except for the use of a different value 3.3 for exponent a in the exponential form of the resonance integral This value of a was determined so that the predicted fluorescence energy from the lowest singlet excited state CB2J in benzene may fit the experimental value. 

Resonance Raman spectroscopy has been applied to studies of polyenes for the following reasons. The Raman spectrum of a sample can be obtained even at a dilute concentration by the enhancement of scattering intensity, when the excitation laser wavelength is within an electronic absorption band of the sample. Raman spectra can give information about the location of dipole forbidden transitions, vibronic activity and structures of electronically excited states. A brief summary of vibronic theory of resonance Raman scattering is described here. 

We must note that we are dealing here not with static molecules, as no molecule is stationary even at the absolute zero of temperature, but rather with non-reacting molecules. This will be extended, however, to include mass spectrometry and the reactions which proceed within the mass spectrometry tube, as these are used to define the structure of the parent molecule. Obviously, though, such reactions have an importance of their own which is not neglected. Details of species involved as reactive intermediates, which may exist long enough for definition by physical techniques, will also be considered. For example, the section on ESR (Section 2.04.3.7) necessarily looks at unpaired electron species such as neutral or charged radicals, while that on UV spectroscopy (Section 2.04.3.3) considers the structure of electronically excited heterocyclic molecules. 

Structure, determination of organic reactivity, 35, 67 Structure and mechanism, in curbene chemistry, 7, 153 Structure and mechanism, in organic electrochemistry, 12, 1 Structure and reactivity of carbencs having aryl substitutents, 22, 311 Structure and reactivity of hydrocarbon radical cations, 38, 87 Structure of electronically excited molecules, 1, 365... 

Solvents, protic and dipolar aprotic, rates of bimolecular substitution reactions in, 5, 173 Spectroscopic observation of alkylcarbonium ions in strong acid solutions, 4, 305 Stereoselection in elementary steps of organic reactions, 6, 185 Structure and mechanism in carbene chemistry, 7, 153 Structure of electronically excited molecules, 1, 365... 

Among a variety of spectroscopic methods, vibrational spectroscopy is most commonly used in structural chemistry. IR/Raman spectroscopy provides information about molecular symmetry of relatively small molecules and functional groups in large and complex molecules. Furthermore, Raman spectroscopy enables us to study the structures of electronically excited molecules and unstable species produced by laser photolysis at low temperatures. Several other applications that are important in structural chemistry are also discussed in this section. 

The importance of electronically excited states in reaction kinetics is well established [14]. Electronic excitation leads to qualitative as well as to quantitative modifications in the preceding theories, especially in connection with the intersection of the potential-energy surfaces corresponding to different electronic states. Structures of electronically excited activated complexes have been studied (for example, [55]) and have been used in postulating kinetic mechanisms for the production of nonequilibrium excited species that have been observed (for example, [56]) in hydrogen-oxygen flames. 

---