We have developed a model vibronic Hamiltonian which successfully reproduces a wide variety of optical spectra (absorption, hole burning, and Stark effect) from the P* band of the photosynthetic reaction center of Rb. sphaeroides. A key component of the model is coupling of the Q(y) states of the special pair bacteriochlorophylls to an internal charge-separated state of the dimer. The model is parametrized to fit wildtype optical spectra and then tested by simulating the absorption and Stark effect spectra from the heterodimer mutants with a minimum of adjustable parameters. The agreement with experiment of the latter results suggests that the basic features of the model are correct.