Problem- Consider an electronic transition of a diatomic molecule in which the up- per electronic state has a larger equilibrium bond distance than the lower state. Determine the value of J for the lower electronic-vibrational state at which the the R-branch wave-number ? ?R(J) is at a maximum before it starts to decline. Then find the value of J at which ? ?R(J) returns to the value ? ?e?e;v?v. Your an- swers should be in terms of the rotational constants B? for the upper and lower electronic vibrational states.
If possible just a brief explanation how you got the answer?