Raman circular intensity differential

Raman circular intensity differentials (c.i.d.), which are observed in methyl asymmetric deformations and methyl torsions, may be valuable in probing chirality in monoterpenoids (—)-limonene and (+)-carvone each show a broad, weak depolarized Raman band at 250 cm-1 with a large c.i.d. The origin of these bands is not yet certain.23... 

Bicyclo[3,l,l]heptanes.—Some i.r. and Raman spectral bands have been assigned for a- and /S-pinene and the Raman circular intensity differential spectrum has been recorded for (-)-ct-pinene. ° ... 

We have been discussing electronic transitions and ultraviolet or visible circular dichroism. However an optically active molecule will also have infrared CD due to its vibrational transitions. The measurement of infrared CD is very difficult, but some data exist [29]. Another related measurement is the Raman circular intensity differential [30]. It is the difference in Raman scattered intensity when right and left circularly polarized light is... 

Barron LD, Buckingh AD (1973) Raman circular intensity differential observatimrs on some monoterpenes. J Chem Soc Chem Commun 152-153... 

It is also interesting to note that circular differential Raman scattering, circular intensity differential (CID), has been reported for a series of optically active sulfoxides and a correlation found between the absolute configuration at sulfur and the differential scattering (240). Thus, all (/ )-alkyl p-tolyl sulfoxides investigated show a common (positive) CID feature in the 300 to 400 cm" region. 

P. L. Prasad and D. F. Burrow. Raman optical activity, computation of circular intensity differentials by the atom-dipole interaction model. J. Am. Chem. Soc., 707 800-805 (197y). 

Further important technical advances include the development of devices for the automatic scanning of the depolarisation ratio, for measuring Raman CID (circular intensity differentials), for measuring difference Raman spectra (i.e. the difference between the Raman signals from solutions and solvents), for studying optical-fibre Raman spectroscopy, for rapid (i.e. picosecond) Raman spectroscopy and Raman micrography 64). 

Nonlinear optical activity phenomena arise at third-order and include intensity dependent contributions to optical rotation and circular dichroism, as well as a coherent form of Raman optical activity. The third-order observables are - like their linear analogs - pseudoscalars (scalars which change sign under parity) and require electric-dipole as well as magnetic-dipole transitions. Nonlinear optical activity is circular differential. 

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