We study a diatomic homonuclear molecule incident upon a potential barrier. We allow for transitions among bound states and for molecular break-up for a molecule incident upon the barrier in a bound state. We apply an elegant method to calculate probabilities of reflection and transmission, in bound and unbound states. In the numerical work, we use a binding potential that captures the important physical features of real potentials and a single delta barrier for the potential barrier. We showed that the probabilities of reflection and transmission in unbound states were small compared to the probabilities of reflection and transmission in bound states. We also found that the probabilities of reflection and transmission decrease for large kinetic energies. For a molecule with only one bound state, it was shown, using two different binding potentials, that the probabilities of reflection and transmission in unbound states were also small. We showed that an arbitrarily weakly-bound molecule will break up upon encountering a barrier. We also discussed a shortcoming of the results and possible resolutions. Suggestions for further studies were also presented.--P.ii.
