X-ray photoelectron spectroscopy of hydrogen and helium
(PHYSorg.com Physics)

For the first time scientists measured the vibrational structure of hydrogen and helium atoms by X-rays. The results disprove the misconception that it`s impossible to obtain X-ray photoelectron spectroscopy (XPS) spectra of hydrogen and helium, the two lightest elements of the Periodic Table. This was thought to be the case due to low probabilities of electron ejection from these elements induced by X-rays.