Temperature-dependence of the Kerr effect of chloromethanes

Abstract
Measurements of the Kerr effect (electric birefringence) are reported for the four chloromethanes (CH3CI, CH2CI2, CHCI3, CCI4) in the vapour phase over a range of temperature (260–370 K). For CCI4, the second hyperpolarisability γK is found to be (1.23 ± 0.04)× 10–60 C4 m4 J–3, in reasonable agreement with other nonlinear optical measurements. For CH2CI2, a polarisability anisotropy parameter (α33α) is determined to be (–0.68 ± 0.08)× 10–40 C2 m2 J–1, demonstrating the inadequacy of the bond additivity approximation. The first hyperpolarisabilities βK of CH3Cl, CH2Cl2 and CHCl3 are relatively small and therefore poorly determined, indicating that hyperpolarisability contributions to the Kerr effect of dipolar molecules may in general be less significant than has previously been suggested.

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