Experimental and theoretical study of the dipole polarizability of ferrocene Fe(C5H5)2

The mean dipole-polarizability α(ω) of ferrocene at 440 K is obtained from measurements of the gas-phase refractivity [n(ϱ,ω)−1] in the frequency range between ω=0.05 au and 0.14 au. α(ω) obtained via quasi-continuous white-light interferometry and from additional absolute measurements at three discrete frequencies (α(0.07198 au) = 131.51(32) au, α(0.08383 au) = 133.74(34) au and α(0.14014 au) = 150.71(1.1) au) has been extrapolated to zero frequency, yielding α(0) = 126.2(1.0) au. The experimental results are compared to those of time-dependent density functional calculations for the staggered and eclipsed conformers. Good agreement between theoretical and experimental results is found (errors are 1% for the static value and 2–4% for α(ω)). A large increase in the polarizability anisotropy of 50% in the measured ω range is found. Hartree-Fock theory fails to predict the correct α(0) value.