The radiative deexcitation probability of the ${}^{2}F_{5∕2}\to {}^{2}F_{7∕2}$ transitions within the $4f$ electronic shell of the ${\mathrm{Yb}}^{3+}$ ion in $\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_3$ exhibits at low temperatures a strong increase with increase of hydrostatic pressure up to $250\mathrm{kbar}$. At the same time only a very small, almost negligible, decrease of the transition energy with pressure is observed. These results are explained by coupling of the $4f^{13}$ with the $4f^{12}5d^1$ electronic configurations and increase of the coupling coefficient with pressure. The mechanism of this process is discussed.

• Received 2 June 2005

DOI:https://doi.org/10.1103/PhysRevB.72.224104