Infrared and Raman Selection Rules for Lattice Vibrations: The Correlation Method

Abstract

With the recent growth in interest in the ir and Raman spectra of crystals, it has become very important to know which vibrational modes are optically active. Hornig, Winston and Halford, and Bhagavantam and Venkatarayudu pioneered in developing methods for this. However, heretofore the determination has been a laborious procedure fraught with difficulty and with many points of indecision. Among the latter is the choice of the primitive cell and the correct site symmetry of each atom. What is needed is a short, straightforward, foolproof method. We propose here an alternate procedure for obtaining the activity of the vibrations from the correlation tables which comes close to meeting these goals. The calculation is reduced to but a few minutes' work. The method will be explained in detail by use of numerous examples.