Estimate the magnitude of the transition dipole moment of a chargetransfer transition modelled as the migration of

Question:

Estimate the magnitude of the transition dipole moment of a chargetransfer transition modelled as the migration of an electron from a H1s orbital on one atom to another H1s orbital on an atom a distance R away. Approximate the transition moment by −eRS where S is the overlap integral of the two orbitals. Sketch the transition moment as a function of R using the curve for S given in Fig. 10C.7. Why does the intensity of a charge-transfer transition fall to zero as R approaches 0 and infinity?

Data in Fig. 10C.7