An investigation of electric-field-gradient-induced Birefringence in fluids.
Ntombela, Siyabonga Sibusiso.
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The theory of electric-field-gradient-induced birefringence (EFGIB, the Buckingham effect) is briefly reviewed, and modifications to the Buckingham-effect apparatus are described. These modifications have increased the throughput of the light reaching the photodiode detector, thereby considerably enhancing the sensitivity of the measurements. In addition, a new PID voltage controller has been built for the high-voltage power amplifier, ensuring stability to better than 0.1% over long periods of time. Room-temperature measurements of the Buckingham effect for gaseous oxygen have been undertaken, allowing for an estimation of the traceless electric quadrupole moment £ of O2. The quadrupole moment has been extracted from the measured data by making the assumption that the temperature-independent hyperpolarizability contribution to the EFGIB is negligible. The limitations of this assumption are discussed. The value obtained for the electric quadrupole moment of O2 is £ = (¡1.033 § 0.027) £ 10¡40 Cm2. The available ab initio quantum-computed values of£found forO2 in the literature are tabulated, and are comparedwith our measured value. Potential future work, where a full temperature-dependent study of the EFGIB of O2 is envisioned, is briefly described.