Zeeman Effect of the 2F5/2, E5/2→2F7/2, E5/2 Transition in CaF2:Tm2+

The Zeeman spectrum of the 2F5/2, E5/2→2F7/2, E5/2 sharp‐line fluorescence in CaF2:Tm2+ gives direct proof that the transition is a magnetic dipole one. The measured excited‐state g value of 0.85 agrees with the Lande value. The line strength has been measured and was found to be significantly smaller than the calculated one.