Thermal Casimir-Polder shifts in Rydberg atoms near metallic surfaces

The Casimir-Polder (CP) potential and transition rates of a Rydberg atom above a plane metal surface at finite temperature are discussed. As an example, the CP potential and transition rates of a rubidium atom above a copper surface at 300 K are computed. Close to the surface we show that the quadrupole correction to the force is significant and increases with increasing principal quantum number $n$. For both the CP potential and decay rates one finds that the dominant contribution comes from the longest wavelength transition and the potential is independent of temperature. We provide explicit scaling laws for potential and decay rates as functions of atom-surface distance and principal quantum number of the initial Rydberg state.

Figure 1

Relative contributions from different transitions to the CP dipole and quadrupole level shift of the state $43s$ of ${}^{87}\mathrm{Rb}$.

Figure 2

(a) Casimir-Polder level shifts of the states $32s$ (dotted line), $43s$ (dashed line), and $54s$ (solid line) of ${}^{87}\mathrm{Rb}$ near a copper surface at 300 K; total shift and quadrupole contribution alone (inset). (b) Spontaneous decay rate near a copper surface at 300 K for the initial states $32s$ (dotted line), $43s$ (dashed line), and $54s$ (solid line) of ${}^{87}\mathrm{Rb}$.