Dimensional perturbation theory: an efficient method for computing vibration-rotation spectra

Large-order perturbation theory in D−12, where D is the dimensionality of space, is shown to be an accurate and computationally efficient method for computing molecular vibration-rotation spectra. Results are presented for the ground vibrational state of CO2 with J as high as 80. The rate of convergence of the perturbation expansion increases with J and the computational cost scales on JNv53, where Nv is the number of vibrational basis functions. Therefore, this approach seems to be especially well suited for treating highly excited rotational states.