Molecular physics with synchrotron radiation

This year marks the 125th anniversary of the founding of The Physical Society of London and its Proceedings, which were launched in 1874, from which the Journal of Physics, and later J. Phys. B: At. Mol. Opt. Phys., originated. In contrast, synchrotron radiation was discovered just over 50 years ago [1]. However its first systematic scientific application, which was in the field of atomic and molecular physics, occurred even more recently in 1963 when Madden and Codling performed their pioneering investigations of the absorption spectra of the rare gases in the VUV [2]. Driven in large part by the demands of atomic and molecular science, dedicated storage rings (second generation sources) soon followed, built specifically as light sources to operate from the IR to the x-ray spectral regions. The use of synchrotron radiation has now extended worldwide to over 70 research facilities in every continent of the world - many of them third-generation machines with insertion devices to enhance performance. Although the rapid increase in computational speed is often cited as a dramatic example of modern technological progress, the increase in brightness of synchrotron light sources has occurred even more rapidly [3]. Not surprisingly numerous additional scientific areas ranging from protein crystallography to materials science have also benefited greatly from this progress. The role of synchrotron radiation in research into atomic, molecular and optical physics continues to expand rapidly as experiments of ever-increasing complexity are combined with increased photon flux and fully characterized polarization. The present special issue of J. Phys. B: At. Mol. Opt. Phys. is intended to bring to the attention of its readers some aspects of current experimental, and theoretically associated, work on synchrotron based studies of molecules that relate to the field of atomic, molecular and optical physics. The research papers on experimental work published in this special issue originate from eight countries and seven synchrotron facilities. The wide range of topics covered includes photoionization processes and dynamics, valence and inner-shell photoelectron spectroscopy, photoabsorption and photofluorescence, photofragmentation and dissociative photoionization and multiple photoionization. The molecules studied range in size from hydrogen, the most abundant and simplest molecule in the Universe, up to DNA, the most important molecule in biology. Some, such as OH, are highly reactive and short-lived. Others, such as fullerene endohedrals, have only recently been discovered. Thus the articles included in this special issue cover a wide variety of exciting topics in the areas of molecular and optical physics. It is hoped, therefore, that this will further stimulate interest and appreciation of the role and importance of synchrotron radiation in the study of molecules. It is, of course, the contributors and referees who have made this thematic issue on molecular physics with synchrotron radiation possible, and they deserve our thanks and appreciation. References [1] Elder F R, Gurewitsch A M, Langmuir R V and Pollock H C 1947 Phys. Rev. 71 829 [2] Madden R P and Codling K 1963 Phys. Rev. Lett. 10 516 [3] Altarelli M, Schlachter F and Cross J 1998 Sci. Am. December 1998