Ultrafast dynamics probed by the time-resolved anisotropy measurements

In this paper, we shall show that in order to effectively observe the quant um beat due to vibrational coherence by the anisotropy measurement, it is n ecessary to perform the frequency-resolved measurement in the transient abs orption. It is found that the quantum beat due to vibrational coherence can not be observed if the ultrafast processes under observation do not involve an electronic transition. In order to effectively observe the quantum beat due to vibronic coherence, it is necessary to perform the frequency-integrated time-resolved anisotro py measurement. We also show that it is usually difficult to obtain accurat e dynamics information from the time-resolved anisotropy measurement.