The present volume shows the diverse applicability of our theoretical methodology for carry out cross section calculations ranging from gaseous targets to the solids. The book covers our modest theoretical efforts to carry out calculations on electron interactions with atomic-molecular targets in condensed/solid phase. Presently the inelastic mean free path (IMFP) of incident electrons is calculated as a function of energy for bulk forms of Si, SiO2 and SiO together with Al2O3 by employing atomic/molecular inelastic cross sections derived by our semi-empirical quantum mechanical method. The present work is important in view of paucity of experimental data on IMFP in solids. we also determine the ionization cross sections for the exotic and lesser known molecular targets CN, C2 N2, HCN, HNC and BF; also for the plasma important targets SiClx (x=1-4). Our success,to be demonstrated in this book conveys the strength of the present theory for such calculations.