Blackbody-radiation correction to the polarizability of helium

The correction to the polarizability of helium due to blackbody radiation is calculated near room temperature. A precise theoretical determination of the blackbody radiation correction to the polarizability of helium is essential for dielectric gas thermometry and for the determination of the Boltzmann constant. We find that the correction, for not too high temperature, is roughly proportional to a modified hyperpolarizability (two-color hyperpolarizability), which is different from the ordinary hyperpolarizability of helium. Our explicit calculations provide a definite numerical result for the effect and indicate that the effect of blackbody radiation can be excluded as a limiting factor for dielectric gas thermometry using helium or argon.

Figure 1

$\chi ({\omega }_B,T)$ as a function of ${\omega }_B$ at $T=273$ K. The frequency scale is in atomic units (a.u.).

Figure 2

A plot of the dimensionless quantity $\chi$ against the temperature $T$ measured in kelvin (K) is shown, with special emphasis on the point $T=273\hspace{0.5em}\mathrm{K}$.