Knowledge Bank

For many years we have investigated the vibrational potential energy surfaces of non-rigid molecules in their ground and excited electronic energy $states.1$ These have been determined from examining the far-infrared, Raman, and fluorescence spectra of the molecules as vapors. A limitation of these studies has been that ample vapor pressures of the samples must be available to record good spectra. In order to overcome this difficulty we have designed a high-temperature Raman cell for studying high-boiling liquids and $solids.2$ This has allowed us to study vapors at temperatures above $300\circ C$. To assist us in these studies we have written a computer program to calculate the vapor-phase Raman band contours of asymmetric top molecules. The experimental and calculated contours for several molecules including 9,10-dihydroanthracene, p-cresol, phthalan, coumeran, 1,3-benzodioxole, indan and 1,4-benzodioxan will be compared. In addition, the use of vapor-phase Raman spectra for the determination of PES's will be discussed.