Determination of potential energy surfaces of linear triatomics from vibration-rotation spectra: An inversion method applied to CO₂

An inversion procedure for obtaining a local stretching/bending three-mode potential for the CO₂ molecule is outlined, and a FORTRAN program for implementing this procedure is presented. The technique is a general one, and should be applicable to any small molecule for which adequate vibration/rotation spectroscopic data are available. The potential surface is obtained in two steps: first, an approximate surface is obtained using the vibrational self-consistent-field scheme to generalize the semiclassical Rydberg-Klein-Rees inversion: this surface is based on approximate inversion method and is unique. Next, a perturbative approach is defined, to obtain an improved surface. While this produces a surface of high accuracy, it is a fitting, rather than an inversion, and may not produce a unique surface. Comments are offered on extension and application of this SCF-based inversion scheme.