Direct observation of a highly forbidden optical transition in Sm:SrF${}_2$

Mohit Verma, Luca Talamo, Hiromitsu Sawaoka +1

The $4f^6$ ${}^7{F}_0$ $\to 4f^6$ ${}^5{D}_0$ intra-configuration transition in Sm:SrF${}_2$ is forbidden for Sm${}^{2+}$ ions in the octahedrally symmetric substitution sites in SrF${}_2$.…