Inference of vibrational anharmonicity in hot SF6: An electron diffraction study

In an investigation of gaseous SF6 at temperatures ranging from 298 to almost 1000 K, the observed thermal expansion of the mean bond length as a function of the mean-square amplitude of vibration was found to be much too large to be accounted for by the commonly invoked model of Morse anharmonicity. Experimental results can be reproduced quantitatively, however, with the aid of existing potential constants fed into an anharmonic, modified Urey–Bradley force field proposed previously.