THE ANISOTROPY OF THE 2ND HYPERPOLARIZABILITY OF MOLECULAR-HYDROGEN FROM THE PRESSURE AND TEMPERATURE-DEPENDENCE OF THE KERR EFFECT

The dc Kerr effect of gaseous hydrogen has been measured with 632.8 nm HeNe laser radiation in the temperature range between -77 and 140°C using pressures up to 120 bar. The data were reduced to the zero-density limit by means of a second-order virial expansion. The temperature dependence of the quantum correction could be clearly resolved. The analysis of the data leads to γ(H2) = (4.15 ± 0.12) × 10-62 C4 m4 J-3 for the anisotropy of the electric hyperpolarizability. A less extensive determination of this quantity in deuterium gas resulted in the value γ(D2) = (4.17 ± 0.16) × 10-62 C4 m4 J-3. The results are discussed in relation to recent ab initio calculations and other non-linear optical experiments on hydrogen. © 1990.