Accessing the non-ergodicity factor of o-terphenyl via multi-line nuclear γ-resonance time-domain interferometry

ABSTRACT

Nuclear γ-resonance time-domain interferometry (TDI) was used to investigate the dynamics of the model glass-former o-terphenyl (OTP) at the $\text{μ}\mathrm{s}$ timescale and close to the peak of the static structure factor ($q_{max}=1.4{\text{Å}}^{-1}$) employing a recently introduced 3-lines scheme. The measured relaxation times (τ) agree with those available in the literature and confirm that in OTP the dynamics are dominated by the structural relaxation at the inter-molecular length-scale and by the Johari–Goldstein (${\text{β}}_{\mathrm{J}\mathrm{G}}$) relaxation at the intra-molecular one. The experimental scheme here employed presents the distinct advantage of providing access to the non-ergodicity factor ($f_q$) on an absolute scale. The extracted $f_q$ values are qualitatively consistent with those derived in the previous neutron scattering experiments, with a very similar wavevector, q, and temperature dependence. Our data thus further establish the capability of multi-line TDI to measure the absolute strength of relaxation processes.

KEYWORDS:

• Relaxation processes
• glass-transition
• nuclear resonant scattering

Acknowledgments

We acknowledge the ESRF for the provision of synchrotron radiation facilities at the Nuclear Resonance beamline ID18, and we thank Dr Harald Müller for the preparation of the o-terphenyl sample and Jean-Philippe Celse for his help in the implementation of the experimental set-up.

Disclosure statement

No potential conflict of interest was reported by the author(s).