[en] This document is a summary of the lectures or seminar talks by A. Mozumder and his discussion/information exchanges with Y. Hatano, A. Yokoya, and Y. Katsumura. A. Mozumder is an invited fellow of the JSPS Invitation Fellowship Program for Research in Japan (Short-Term) with the host Y. Hatano, and stays in Japan mainly at Advanced Science Research Center (ASRC) of JAEA for 52 days starting from September 27 through November 17, 2007. The research in this program is entitled 'Charged Particle and Photon Interactions with Matter', from which the authors give the title of this document one of the most important reactive species commonly produced in matter from these interactions. This document contains the annotated materials presented at ten seminars given by A. Mozumder during his stay in Japan in this program at JAEA (Tokai and Takasaki) and also at various universities and research institutes, including invited lectures at the International Symposium of ASR2007 held in Tokai and the Annual Discussion Meeting of Radiation Chemistry held in Kyoto. Some information exchanged frequently at informal discussion with the group of Y. Katsumura and A. Yokoya at ASRC are also incorporated. The following write-up is divided into five sections, according to the subject matters discussed. These are respectively as follows. (1) Early Stages in the Radiolysis of Liquid Water: Consequences of Excitation, Ionization and Dissociative Electron Attachment. (2) Differential Oscillator Distribution (DOSD) in Liquid Water and G-values of Excitation and of Ionization. (3) Quasi-Ballistic Model of Electron Mobility in Liquid Hydrocarbons including Thermodynamics, Scavenging and Relation Between Free-Ion Yield and Mobility. (4) Electron Localization: The Anderson Model. And (5) Free-ion Yield in Liquefied Rare Gases: A new Theoretical Model. (author)