Analysis of the ground configuration ofTm3+in CaWO4

Abstract

The energy levels of the $^{1}D$, $^{1}G$, $^{3}F$, and $^{3}H$ terms of ${\mathrm{Tm}}^{3+}$ in CaW${\mathrm{O}}_{4}$ were established by an analysis of the absorption and fluorescence spectra. The absorption lines were used to establish most of the energy levels recorded over the wavelength range from 2.5 \ensuremath{\mu}m to the band edge at about 0.3 \ensuremath{\mu}m with crystals at temperatures from 2 to 300\ifmmode^\circ\else\textdegree\fi{}K. Transitions to the levels of the $^{3}H_{6}$ ground multiplet were observed in fluorescence. An energy-level scheme was constructed by using electric dipole selection rules and by the aid of theoretical calculations. The ground state was identified as a singlet ${\ensuremath{\Gamma}}_{2}$; this is consistent with no electron paramagnetic resonance at 9 or 36 GHz, as reported by Kirton. The 1.911- and 1.916-\ensuremath{\mu}m laser lines reported by Johnson appear in fluorescence as transitions from a $^{3}F_{4}$ ${\ensuremath{\Gamma}}_{1}$ at 5594 ${\mathrm{cm}}^{\ensuremath{-}1}$ to ${\ensuremath{\Gamma}}_{3,4}$ and ${\ensuremath{\Gamma}}_{2}$ levels at 370 and 384 ${\mathrm{cm}}^{\ensuremath{-}1}$. This is well above the energy position of 325 ${\mathrm{cm}}^{\ensuremath{-}1}$ for the terminal level reported by Johnson. The calculations were made by diagonalizing a Hamiltonian that describes the free ion and the crystal field in a basis of states spanning the entrie $4{f}^{12}$ configuration. In a least-squares calculation, an rms deviation of 6.7 ${\mathrm{cm}}^{\ensuremath{-}1}$ between the theoretical and experimental energy levels was obtained. Calculated energy levels are given for the entire ${\mathrm{Tm}}^{3+}$ ground configuration along with ${g}_{\ensuremath{\parallel}}$ factors for the doublet ${\ensuremath{\Gamma}}_{3,4}$ levels.