Mössbauer studies related to the solid-state dynamics of C60 |
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Authors: | R H Herber E Bauminger I Felner |
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Institution: | (1) Racah Institute of Physics, The Hebrew University, 91904 Jerusalem, Israel |
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Abstract: | Summary C60 (Buckminsterfullerene) is isolated from organic solvents above 260 K as an f.c.c. solid with complete orientational disorder.
The rotational dynamics are diffuse and isotropic, with a short (12 ps) correlation time at 300 K. Below 260 K, the solid
forms in a simple cubic lattice withPa3 symmetry. The librational motion occurs by activated jumps with a correlation time of about 60 ns at 200 K. To gain further
insight into the dynamics of C60, the compound C60Fe(CO)4 (I) (generously made available to us by A. Stephens and M. Green of Oxford University) has been studied by57Fe M?ssbauer spectroscopy. As expected, the resonance at 90 K consists of a doublet with an isomer shift (relative to metallic
iron) of 0.034(1) mm s−1 and a quadrupole splitting of 1.607(5) mm s−1. There is no significant temperature-dependent, intensity asymmetry of the doublet. The temperature dependence of the effect
magnitude is well fit by a linear regression over the range 85<T<210 K. To elucidate the relationship of these results to the effect of the C60 moiety in I, further lattice dynamical M?ssbauer studies have been carried out on (maleic anhydride) Fe(CO)4 (II), one of the few isolatable tetracarbonyl complexes of iron. For (II), the quadrupole splitting is 1.371(5) mm s−1 at 90 K, and the temperature, dependence of the isomer shift is smaller than it is for (I), while the temperature dependence
of the recoil-free fraction is significantly larger in (I) than in (II).
Paper presented at ICAME-95, Rimini, 10–16 September 1995. |
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Keywords: | M?ssbauer spectra |
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