  Contact electrification (CE) (or triboelectrification) is the phenomena where
charges are produced through physical contact between two materials. Here we
report the atomic featured photon emission spectra during CE between two solid
materials. Photon emission provides the evidence that electron transfer takes
place at the interface from an atom in one material to another atom in the
other material during CE. This process is the contact electrification induced
interface photon emission spectroscopy (CEIIPES). It naturally paves a way to a
spectroscopy corresponding to the CE at an interface, which might impact our
understanding of the interaction between solids, liquids, and gases. The
physics presented here could be expanded to Auger electron excitation, x-ray
emission, and electron emission in CE for general cases, which remain to be
explored. This could lead to a general field that may be termed as contact
electrification induced interface spectroscopy (CEIIS).
