Correlated Electron Paramagnetic Resonance and Optical Study of Cd $F_{2}$ : ${Er}^{3 +}$ . I. $C_{2 v}$ Local-Site Symmetry

A correlated E PR and optical study has been performed on Cd

F_{2}

: (

{Er}^{3 +}

U

) (

U \equiv unintentionally compensated

) and Cd

F_{2}

: (

{Er}^{3 +}

M^{+}

) (

M^{+} = {Li}^{+}, {Na}^{+}, {Ag}^{+}, or K^{+}

) crystals with the following objectives: (i) generating a high concentration of a specific (i.e.,

C_{2 v}

)

{Er}^{3 +}

site through the addition of monovalent cations and characterizing this site by EPR; (ii) unambiguously determining selected optical properties of

{Er}^{3 +}

C_{2 v}

symmetry; and (iii) determining the crystal field splitting of the

{}^{4}I_{\frac{15}{2}}

ground site of

{Er}^{3 +}

for

C_{2 v}

symmetry. The orthorhombic (

C_{2 v}

) symmetry, produced at the erbium site when

M^{+}

ions are introduced for charge compensation, has been identified through the angular dependence of the

{Er}^{3 +}

EPR spectrum (at 4.2 K). Moreover, the EPR results reveal that the

C_{2 v}

(

{Er}^{3 +}

M^{+}

) site accounts for nearly all (> 98%) of the noncubic sites recorded for (

{Er}^{3 +}

M^{+}

) specimens. This result has permitted an unambiguous determination of the emission, excitation, absorption, lifetime, and efficiency properties of

{Er}^{3 +}

C_{2 v}

symmetry. These characteristics have been found to be similar for each of the

M^{+}

ions listed, but different from those obtained from (

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Correlated Electron Paramagnetic Resonance and Optical Study of CdF2: Er3+. I. C2v Local-Site Symmetry