Introduction

In the Introduction to the second part of the book, we provide an overview of Raman scattering. We delve into the historical context surrounding the discovery of the Raman effect and highlight significant precursory research. Emphasizing the inherent quantum nature of this phenomenon, we introduce the concept of quasiparticles, specifically phonons and vibrons. Our discussion involves a critical examination of the commonly used concept of virtual levels for explaining Raman scattering. Additionally, we introduce and pave the way for in-depth explanations of surface-enhanced Raman scattering (SERS), stimulated Raman scattering (SRS,) and coherent anti-Stokes Raman scattering (CARS), both of which are elaborated upon in subsequent sections of the book.