Temperature dependence of electric field-gradient induced birefringence (Buckingham effect) and molecular quadrupole moment of N₂. Comparison of experiment and theory

Observations of electric field-gradient induced birefringence (the Buckingham effect) in gaseous N₂ over a range of temperature (≈293–412 K) and pressure (up to ≈2000 kPa) are reported. Analysis of the data shows that the temperature-independent contribution to the effect is not negligible, and values of the molecular hyperpolarizability, B, and quadrupole moment, ⊖, are derived. In the case of the quadrupole moment, the experimental value [⊖=(−4.97±0.16)×10⁻⁴⁰ Cm²] and a state-of-the-art ab initio value [⊖=(−4.93±0.03)×10⁻⁴⁰ Cm²] due to Halkier, Coriani and Jørgensen [Chem. Phys. Lett. 294 (1998) 292] are in excellent agreement.