Appendix Overview of Decay Kinetics

Single exponential kinetics occurs in the basic situation when the decay rate at time t is proportional to the population N(t) via a constant coefficient k, 

Acknowledgements. A number of people contribute daily to the realization of exciting new ultrafast experiments, and without their work we could not have written this chapter. In particular we would like to thank Giulio Cerullo, 

Mauro Nisoli, Salvatore Stagira and Margherita Zavelani-Rossi. Thanks go also to Sandro De Silvestri for his continued support of our activity. We are grateful to Dr. Maddalena Patrini and Prof. Franco Marabelli for several stimulating discussions on the study of semiconductor optical constants in the friendly environment of the Optical Spectroscopy Laboratory at the A. Volta Department of Physics, University of Pavia. 

Finally, very special thanks are due to Prof. Giovanna Dellepiane, to whom both authors owe a great deal. She introduced us to this exciting research field, and was teacher and leader for several years, giving us the encouragement and motivation to forge ahead. 

Financial support from the Ministry of University, Scientific and Technological Research is also gratefully acknowledged. 

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