Question

Naïve users of spectroscopy often think that the intensity of a transition is a direct function of the energy of the transition. Can you conjecture why this misconception is so common? Is it completely wrong? What is the common factor (quantum mechanically) that relates to the intensity of a spectroscopic transition either by absorption or emission? The spontaneous emission is inversely proportional to the lifetime of the excited state ( check units of Aij ). Might there be some tie between the Uncertainty Principle and Aij? Explain.

Answer 1

Intensity of transition does not depend on energy of transition. It is depends on boltzman distribution function i.e ratio of molecule in exited stte and number molecule in ground state. Number of molecule in exicted depends on intensity of energy source which cause exiction.

intensity of transition =   ratio of molecule in exited stte and number molecule in ground state

Lifetime and uncertainty of energy level is proposionaly related which ultimately relate to peak brodning in spectroscopy.