Measurement uncertainty emerging methods

The exact temperature of the phase transition in the experiments above is subject to some uncertainty, which we attribute to the stoichiometric variations in both the central atom of the counterion (P,As) and the type of the halide. The picture that emerges, however, is compatible with the full scope of experimental results a dynamic Jahn-Teller effect at high temperature, a structural phase transition in the 120-150 K range, and a distortion of the molecular ion in the low-temperature phase, arising from the positive synergy of the cooperative Jahn-Teller effect and the low symmetry of the environment. The static-to-dynamic transition does not coincide with the structural transition and its temperature depends on the detection method whereas ESR spectra are isotropic at room temperature, infrared lines are still split, indicating a distorted state on the time scale of the measurement. This... 

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