High energy levels and high-energetic emissions of the trivalent holmium ion in LiYF4 and YF3

The luminescence of LiYF4 and YF3 doped with Ho3+ was investigated using synchrotron radiation. In the excitation spectra transitions to previously unidentified 4f10 levels were observed thus extending the energy level diagram of Ho3+ into the (vacuum) ultraviolet region of the electromagnetic spectrum. Some high energy emissions were observed and could be attributed to spin forbidden 4f95d→4f10 emissions in YF3 and LiYF4. For YF3 doped with Ho3+ emission from the 3P(1)2 level (situated at 63000 cm−1) was observed. Furthermore, several photon cascade emission processes were observed in which one VUV photon is converted into two or three UV/Vis photons, albeit with a low efficiency.