Question

Briefly describe what is entailed in a Raman spectroscopy experiment and how it differs from infrared (IR) spectroscopy; e.g., why is it relatively straightforward to record Raman spectra down to low frequency (e.g. ,below 500 cm-1), but more difficult to record IR spectra at low frequency? Explain whether or not IR and Raman spectroscopy differ in terms of the information that is obtained. plz give me the reference

Answer 1

Vibrational Raman spectra can be studied in aqueous solutions without solvent interference.This is due to the fact that water shows WEAK LINES in the 300-3000 cm^- range.IR cannot be studied using water as solvent because of strong solvent interference.

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Other advantages of Raman spectroscopy over IR spectroscopy

1.Raman spectroscopy can be used to study homo diatomic molecules with zero dipole moment.

Information about the internuclear distance,force constant and zero point energy for these molecules can be obtained using Raman spectra.

2.Raman spectrscopy is used to detect totally symmetric vibrationas in molecules.Polarized Raman spectra help us to decide the geometry of molecules.

3..Glass cells can be used in Raman studies whereas salt cells are use for IR work.Salt cells are more difficult to handle.

4.Ramn spectra are much simpler since overtone and combination are small compared the principal Raman lines

5The intensity of a Raman line is proportional to the concentration of the substance whereas a logrithmic relationship exists between intesity and concentration in IR spectroscopy.

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A few good references spectroscopy:

Colin N. Banwell, Elaine M. McCash, Fundamentals of Molecular Spectrosopy, McGraw Hill, 4th ed., London, 1994

Ira N. Levine, Molecular Spectroscopy, Wiley, New York, 1975

John M. Brown, Molecular Spectroscopy, Oxford Chemistry Primers Vol. 55, Oxford Science Publications, Oxford, 1998 ISBN: 0-19-855785-X

G. Herzberg, The Spectra and Structures of Simple Free Radicals, Dover, New York, 1988 ISBN: 0-486-65821-XP. F. Bernath, Spectra of Atoms and Molecules, 2^nd ed., Oxford U. P., New York, 2005 ISBN: 0-19-517759-2 [1^st Ed. with OCR]

Jeanne McHale, Molecular Spectroscopy, Prentice-Hall, 1999 ISBN: 0-13-229063-4 [with color cover]

My favorite is

Colin N. Banwell, Elaine M. McCash, Fundamentals of Molecular Spectrosopy, McGraw Hill, 4th ed., London, 1994