Features of the Transient Absorption

The initial transmission decrease is caused by excited state absorption (ESA) which appears as soon as the molecule is promoted to the Sj state. The subse- 

We obtained very similar experimental results for HBO [29], OH BA [35], and HAN [36] (see Fig. 11.6 and 11.7). They all exhibit a delayed transmission increase and pronounced oscillatory signal contributions with a couple of frequencies in the range up to 700 cnr, as can be seen from the Fourier transforms of the oscillatory contributions depicted in Fig. 11.6 and 11.7 as insets. This observation was also made for a number of other ESIPT compounds [30-32]. 

The analysis of the experimental results is performed by fitting a model function S(t) to the time traces of all applied probe wavelengths [33]. The function consists of a transmission decrease Sesa(I) at time zero due to ESA and a transmission increase which rises step-like with a small delay and reflects the onset of 

In the following we concentrate on the delay of the emission rise and the oscillatory contributions. For HBT we find a delay of 33 fs in the blue wing and of 55 fs in the red wing of the emission spectrum [33]. In the case of HBO, OHBA and HAN the delay is determined to be 80 fs, 45 fs and 30 fs. The fitted frequencies of the oscillatory contributions match the Fourier transformations depicted in Fig. 11.6 and 11.7. Comprehensive listings of the fit results are given in Refs. [33, 35, 36]. 

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