Volume I of the second edition, subtitled Semi-Classical Concepts , presents x-ray science through the semi-classical framework of light and matter. The opening chapter, Introduction and Overview , remains largely unchanged from the first edition. It sets the stage for both volumes of the new edition by reviewing the revolutionary advances in x-ray science driven by synchrotron radiation sources and x-ray free-electron lasers. The following chapters are organized into two parts. Part I establishes the equivalence between wave-based and conventional quantum descriptions of light, which form the foundation of the semi-classical approach. It also discusses the generation of synchrotron and XFEL radiation, now extended to recent accelerator breakthroughs that enable the creation of diffraction- and transform-limited x-ray pulses reaching into the attosecond regime. Part II applies the semi-classical treatment to describe how x-rays interact with matter, whether through an individual atomic or collective dielectric response. Topics include x-ray absorption, dichroism, emission, scattering, and diffraction, extensively illustrated with experimental results.

Special emphasis is placed on polarization-dependent, resonant responses--key to the unique atomic and chemical specificity of x-rays and their ability to probe the charge and spin structure of matter. The final chapter explores real-space and diffractive imaging techniques, with a focus on solving the phase problem through holography, over-sampling, ptychography, and multi-wavelength anomalous diffraction. An appendix provides reference material, including physical symbols, SI units and values, resonant line shapes, the Dirac d-function, and a concise overview of Fourier transform methods and Parseval's theorem.