Precision spectroscopy of X-ray polaritons

When light interacts with matter, it may be deflected or absorbed, resulting in the excitation of atoms and molecules; but the interaction can also produce composite states of light and matter which are neither one thing nor the other, and therefore have a name of their own – polaritons. These hybrid particles, named in allusion to the particles of light, photons, have now been prepared and accurately measured for the first time in the field of hard X-rays by researchers of DESY, ESRF in G