KERR-EFFECT AND POLARIZABILITY TENSOR OF GASEOUS ETHENE

The pressure dependence of the electric field induced birefringence of ethene has been measured for lambda = 632.8 nm, at different temperat ures. Evaluation of the molar Kerr constants after extrapolation to ze ro density yielded gamma(K) = 5.62(28) x 10(-61) C-4 m(4) J(-3) for th e hyperpolarizability anisotropy and delta(KE)(2) = 3/2(alpha(1) alpha (1)(0) + 2 alpha(2) alpha(2)(0)) = 3.058(52) x 10(-80) C-4 m(4) J(-2), where alpha(i) alpha(i)(0), i = 1, 2, are the standard optic and stat ic polarizability anisotropies, respectively. Combining delta(KE)(2) w ith data of other experimental methods as well as a theoretical disper sion relation leads to the complete polarizability tenser of the free ethene molecule: alpha(xx) = 4.41(4), alpha(yy) = 3.79(3), and alpha(z z) = 5.94(2) at lambda = 632.8 nm, and alpha(xx)(0) = 4.30(4), alpha(y y)(0) = 4.09(3), alpha(zz)(0) = 5.81(2) (all in 10(-40) C-2 m(2) J(-1) ; z along the double bond, y perpendicular to the molecular plane).