Time-dependent theoretical treatment of intervalence absorption spectra. Exact calculations in a one-dimensional model

Intervalence absorption spectra are calculated and interpreted by using the time-dependent theory of spectroscopy and the Feit and Fleck method of numerically integrating the time-dependent Schrödinger equation. These methods give exact eigenvalues and eigenfunctions (within the constraints of the model and the numerical accuracy of the computer implementation). The results provide a new physical picture of the absorption spectrum and emphasize that Born-Oppenheimer separation of electronic and vibrational wave functions does not apply to the problem. The details of the calculation are discussed and interpreted. The exact calculation is compared to results obtained in the adiabatic limit. The effect of the temperature on intervalence absorption spectra is discussed. Localization and delocalization are interpreted in terms of the eigenfunctions.