Observation of Tri-photon K-Shell X-Rays

We report the observation of coincidence of three K-shell x-rays generated from the long-lived rhodium isomer excited by bremsstrahlung irradiation. Our previous report revealed that the E3 Mössbauer transition has anisotropic emission due to anisotropic gravitational acceleration Chin. Phys. Lett. 22 (2005) 2530. Now, from broader energy-resolved spectra, we further discover abnormal coincidences and abnormal sum energies of the three K-shell x-rays. The coincidence cannot be explained by currently understood photon statistics, since the measured tri-photon count and the pile-up estimate differ by three orders of magnitude.