X-ray experiments have been used widely in materials science, and conventional spectroscopy has been based on linear responses in light-matter interactions. Recent development of ultrafast light sources of tabletop lasers and X-ray free electron lasers reveals nonlinear optical phenomena in the X-ray region, and the measurement signals have been found to carry a further wealth of information on materials. This book overviews such nonlinear X-ray spectroscopy and its related issues for materials science. Each chapter is written by pioneers in the field and skillfully reviews the topics of nonlinear spectroscopy including X-ray multi-photon absorption and X-ray second harmonic generation. The chapters are divided depending on photon wavelength, ranging from extreme ultraviolet to (soft) X-ray. To facilitate readers' comprehensive understanding, some of the chapters cover the conventional linear X-ray spectroscopy and basic principles of the non-linear responses. The book is mainly accessible as a primer for junior/senior- or graduate-level readers, and it also serves as a useful reference or guide even for established researchers in optical spectroscopy. The book offers readers opportunities to benefit from cutting-edge research in this new area of nonlinear X-ray spectroscopy.

Autorentext

Iwao Matsuda is a professor at the Institute for Solid State Physics (ISSP), the University of Tokyo. His work involves surfaces/interfaces, atomic-thin layer materials, X-ray free electron laser, synchrotron radiation, and spectroscopy. He received his Doctor of Science degree from the University of Tokyo in 2001. After professional experience as a postdoc fellow at the University of Zurich and a research associate at the University of Tokyo, he was appointed as an associate professor at ISSP in 2006 and has served in the current position since 2021. He has received 8 awards and was named a fellow of the Japan Society of Vacuum and Surface Science (JVSS). He has published more than 250 peer-reviewed articles in international journals and review articles. Further, he also actively engages in publishing, including editing three books and contributing chapters to books.

Ryuichi Arafune is a principal researcher at the Research Center for Material Nanoarchitecture(MANA), National Institute for Materials Science (NIMS). His research primarily focuses on inelastic vibrational excitation in photoemission and the tunneling process, spin-orbit interaction in photoexcited states at solid surfaces, and the synthesis of two-dimensional materials. He obtained his Doctor of Engineering degree in Electronic Engineering from Tohoku University in 1998. After accumulating professional experience as a postdoctoral researcher at institutions like Tohoku University, RIKEN, and the University of Tokyo, he also served as a PRESTO researcher of the Japan Science and Technology Agency. Subsequently, he moved to the position of scientist at the International Center for Material Nanoarchitechtonics, NIMS as an independent researcher in 2013. After that, he transitioned to a researcher position in 2017. Additionally, from 2013 to 2017, he held the position of adjunct lecturer at the University of Tokyo. He has been serving in his current capacity since 2023. He was the recipient of the Young Scientist Presentation Award from the Japan Society of Applied Physics and the Outstanding Paper Award from the Surface Science Society of Japan (currently known as JVSS).