HIGH SPIN MOLECULES: S = 7/2 $GdF_{3}$ AND $GdH_{3}$
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Date
1980
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Ohio State University
Abstract
The ESR spectrum of $GdF_{3}$ trapped in solid neon at $4^{\circ} K$ was in accord with its known pyramidal($C_{3v}$) structure and indicated a multiplicity of eight, therefore an $B_{A_{1}}$ ground state. The zero-field-splitting parameter was found to be $|D| = 0.435 cm^{-1}$ with $g_{\perp} = 1.991$ (assuming $g_{\|} = g_{e}$). Hyperfine splitting due to $^{155,157}$Gd were detected [|$A_{\perp}(^{155}Gd)| = 159(6)$ MHz, $|A_{\|} (^{155}Gd)|$ = 365(6) MHz], but the $^{19}F$ hfs was too small to be observed, indicating very ionic bonding. |D| and the $|A_{i}|$ are large compared to values found for $Gd^{3+}(^{8}s_{7/2})$ ions in crystalline lattices. The similar, but weaker, spectrum of $GdH_{3}$ yielded $|D| =0.546 cm^{-1}$, assuming $g_{\perp} = 1.982$ (as for $GdF_{3}$ in solid Ar) and $g_{\|} = g_{e}$. The hyperfine constant were $|A_{\perp}(^{155}Gd)|= 56(6)$ MHz, $|A_{\|}(^{155}Gd)|= 69(6)$ MHz, but the hfs due to $^{1}H$ nuclei was too small to be resolved. The increase in |D| when H replaces F as a ligand is unusual and may indicate that $GdH_{3}$ is planar rather than pyramidal.
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