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

Nuclear γ-resonance time-domain interferometry (TDI) was used to investigate the dynamics of the model glass-former o-terphenyl (OTP) at the μs timescale and close to the peak of the static structure factor (q_max=1.4 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 (β_JG) 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.