Knowledge Bank

An interferometric method has been used to study the far infrared spectrum of sulfur dioxide. First, absorption contours from 15 to $105cm-1$ have been obtained at a resolution of $0.25cm-1$. Comparision of these contours with theoretical contours with theoretical contours computed with molecular constants determined from available microwave data shows satisfactory agreement up to about $76cm-1$ only. To make possible a more detailed analysis of the discrepancies, another set of contours for the frequency range 76 to $104cm-1$ has been obtained at the higher resolution of $0.125cm-1$. This analysis indicates that centrifugal distortion corrections of sixth and higher order in the powers of the angular momentum components may produce appreciable shifts in this frequency range. Approximate values of sixth order c.d. parameters, estimates for some of the eighth order parameters, and the corresponding corrections to the rigid rotor constants and to the fourth order c.d. parameters have been determined by an analysis of the available far infrared and microwave data. It appears impossible to obtain a similarly complete and accurate set of molecular constants from the microwave data alone.