Cavity electron

Figure 5 (a) Typical end-of-pulse absorption spectra obtained in pulse radiolysis of room temperature liquid acetonitrile (7-nsec fwhm pulse of 20 MeV electrons). The 500-nm peak is from anion-2 (dimer radical anion) the 1450-nm peak is from anion-1 (cavity electron), (b) Energy diagram and sketches of anion-1 and anion-2 (see the text). 

The NIR location of the absorption band for a hypothetical cavity electron in acetonitrile makes even more sense if one recalls that there is a linear correlation between the position of the band maximum of a cavity electron in a given polar liquid and the position of the CTTS band maximum for a given halide anion in the same liquid [46,54]. 

While anion-2 is clearly the dimer radical anion of acetonitrile, identification of anion-1 as a cavity electron requires caution. First, we stress that anion-1 cannot be the monomer anion of acetonitrile. The monomer anion does not absorb in the NIR [30,46,52]. For the monomer anion to occur at all, the neighboring acetonitrile molecules should all be oriented in the same direction, as in p-acetonitrile otherwise, coupling to a neighboring (antiparallel) molecule reduces the overall energy and causes instant dimer formation. It is difficult to see how such a fortuitous orientation could persist for 0.3-3 nsec in a room temperature liquid. Also, it is not clear why a monomer anion would... 

In the previous four sections, several solvent radical ions that cannot be classified as molecular ions ( a charge on a solvent molecule ) were examined. These delocalized, multimer radical ions are intermediate between the molecular ions and cavity electrons, thereby bridging the two extremes of electron (or hole) localization in a molecular liquid. While solvated electrons appear only in negative-EAg liquids, delocalized solvent anions appear both in positive and negative-EAg liquids. Actually, from the structural standpoint, trapped electrons in low-temperature alkane and ether glasses [2] are closer to the multimer anions because their stabilization requires a degree of polarization in the molecules that is incompatible with the premises of one-electron models. 

Batsakis JG, Jacobs JB, Templeton AC (1983) Hemangio-pericitoma of the nasal cavity Electron-optic study and clinical correlations. J Laryng Otol 97 361-368... 

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