Infrared spectroscopy using synchrotron radiation source

Abstract

A wide range of important phenomena in condensed matter, such as the molecular and lattice vibrations, free carrier dynamics and various electronic excitations, have their characteristic frequencies and energy ranges that are covered by the infrared (IR) radiation. Accordingly, the IR spectroscopy has been one of the most popular experimental techniques in various fields of basic science and industrial research. The most commonly-used IR source has been the thermal source, which utilizes the black-body radiation from a rod of SiC heated to about 1500K. Although such thermal sources are widely used in commercial IR spectrometers, they have a drawback of low brightness: it can deliver only a low intensity of IR radiation when a small region of the sample must be studied with a microscope. To overcome this, the synchrotron radiation (SR) has been utilized as a bright IR source. SR is emitted by a high energy electron beam passing through a magnetic field, and has a high brightness and low beam divergence. These characteristics make an ideal IR source for microscopy and other studies with a limited sample space, such as high pressure and high magnetic field studies. Using IR-SR, microscopy with a diffraction limited beam diameter on the sample, of the order of wavelength (~10 μm), has been made possible. In this presentation, I will first review the basics of IR SR research. Then, I will discuss the IR-SR research activity at SPring-8 in Japan, which is one of the major SR facilities in the world. In particular, I will discuss our recent high pressure IR studies of strongly correlated electron materials such as YbS, PrRu₄P₁₂, and SrFe₂As₂, where the high pressure has been generated with a diamond anvil cell.