Abstract
The electric quadrupole moments of carbon dioxide and carbonyl sulphide have been measured via the technique of electric-field-gradient-induced birefringence (the Buckingham effect). Measurements for carbon dioxide span the temperature range 299.4 to 471.7 K, which allows for separation of the temperature-independent hyperpolarizability term from the temperature-dependent quadrupole term, yielding a quadrupole moment of Θ = (−14.31 ± 0.74) × 10−40 C m2, and a hyperpolarizability term of b = (−0.34 ± 0.19) × 10−60 C3 m4 J−2. Thermal decomposition of carbonyl sulphide at elevated temperatures restricted our measurements for this molecule to room temperature (302.1 K), yielding a quadrupole moment of Θ = (−0.984 ± 0.034) × 10−40 C m2, the hyperpolarizability term having been assumed to contribute negligibly.
Acknowledgements
The authors wish to express their gratitude to Professor A.D. Buckingham for helpful suggestions. This work has been supported by the South African National Laser Centre (NLC). N.C. also gratefully acknowledges the award of a National Research Foundation (NRF) scholarship.