Relaxation Theory for Modulation Excitation of Vibronic States

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Abstract
One method for the absolute measurement of rate constants for defined quantum states is to study their response to sharply defined pumping. Such an experiment is the observation of the relaxation process after excitation of selected vibronic levels with amplitude modulated light. The observation could either involve secondary absorption or radiative emission. A general stochastic theory is formulated here for these time‐defined processes, in this case, undergoing vibronic relaxation and fluorescence emission. From the general transport matrix describing the relaxation problem via the master equation, the observables are an unambiguous consequence. The solution is given in a form suitable for direct computation. For this particular case, the theory predicts a phase angle in terms of a many‐shot expansion, which is not restricted to exponential fluorescence decay.