Tsing Hua Univ, Dept Engn Phys, Beijing 100084, Peoples R China
; Tsing Hua Univ, Key Lab Atom & Mol Nanosci, Beijing 100084, Peoples R China
; Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China
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 Mossbauer 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.