The process of photon induced vacancy creation in atomic inner shell and decay of the vacancy by prompt x-ray emission is called x-ray fluorescence (XRF). XRF studies have vast applications in the fields of elemental analysis, nuclear, atomic and molecular Physics. The book deals with vacancy alignment in atomic inner shells. As both, the theoretical evaluations and the experimental findings of alignment, involve photoionization cross-sections at specific energies, this book therefore, provides a computer program "LSPICS" to generate L sub-shell photo-ionization cross-sections. A detailed stress is given on quantum based alignment evaluations and predominating corrections at energies of experimental interest. On experimental side, it provides details of XRF set ups including thorough treatments of each X-ray emission and analysis to remove the existing ambiguity among different research groups. The book brings together in-depth discussions of x-ray analysis and quantum approximations. The book is designed to be of interest to spectroscopists, Physicists, Biologists, metallurgists, researchers, upper-level undergraduate, graduate and post-graduate students in these disciplines.