Magnetic optical rotation in H2 and D2

Results are reported of the first definitive calculation of the Verdet constant for H2 and D2. This constant governs the Faraday effect. A new and compact formalism is introduced and applied with the aid of explicitly electron correlated wave functions. After ro-vibrational and thermal averaging (factors which affect the results by about 10%), our values are in good agreement with the experimental ones, which, at best, are probably only accurate to 1%. Approximations and an appropriate dispersion formula are also discussed. Our results show that for H2 and D2 the exact constant is almost exactly proportional to the so-called normal Verdet constant for the experimentally accessible frequencies. The recommended dispersion formula for H2 is V≂2.0701 (ℏω/Eh)2/[0.2435−(ℏω/Eh)2]2×10−7 rad e a0 ℏ−1.