Synchrotrons and x-ray absorption spectroscopy:  what are they and what can they do for you?

Synchrotron radiation (SR) is the light emitted by electrons as they are caused to change direction by magnets while circulating in storage rings at nearly the speed of light. It is successfully used in leading-edge scientific research and technologies. This light is produced over a broad spectral range, from infrared to hard x-rays of tens of kilovolts and is a million to a billion times more intense than that produced by more conventional sources, such as x-ray tubes. Among the different techniques that take advantage from the synchrotron light there is x-ray absorption spectroscopy (XAS). Its development and popularity are strictly linked to the proliferation of SR facilities around the world. XAS is a structural technique, very complementary to diffraction, to investigate the short-range environment around selected atomic species and the electronic structure in condensed matter. Over the last four decades it has progressed from being a technique only suitable for specialists to becoming a tool applicable to many scientific disciplines. Through some examples, I will show how synchrotron and XAS can solve some scientific issues related to fundamental physics. As well, in the broad field of Materials science, XAS is able to shed some light into the general paradigm that correlates the functionality of a material to its structure at atomic level. I will demonstrate that XAS in operando conditions can characterize the redox chemistry and relate the electrochemical mechanism to the local structure behaviour of new generation batteries for automotive applications.