Systematic Approach to the Analysis of Perturbed Spectra. Part I: Statement of the Problem

Abstract

The interpretation and analysis of perturbed molecular spectra is an interesting and challenging activity. Moreover as the resolution and precision of molecular data improves, a systematic and manageable approach to the problems of interpretation and analysis is mandatory. Such a notion may seem a little radical to many scientists, but let us consider the importance of the determination of a complete anharmonic potential function for even the simplest polyatomic molecules. Without molecular model parameters, recovered from the highest quality spectral data, such determinations are doomed to mediocrity. Consider, also, the simulation of the propagation characteristics of infrared radiation through plantetary atmospheres. Without precise molecular parameters, such simulations, though they may be pretty and interesting, are about as valuable scientifically as 30-year-old MO wave functions for a pentatomic molecule. It is not only necessary to be able to recover precise molecular model parameters from the highest resolution molecular spectra, it is also necessary to be able to calculate molecular rotation-vibration energy levels with extremely high precision (on the order of 1% of the Doppler width of a typical transition). Such precision is particularly important in the prediction of long path atmospheric transmission properties for monochromatic radiation.