A caesium atom in its ground state sits between two parallel plates in vacuum
PHYSICS · Multi-part · Fermi University Physics · Atomic, Molecular & Optical Physics · Radiative transitions, external fields and collisions · Radiative transitions, external fields and collisions
Reading the Spectrum, Ch Atoms in an electric field: the Stark effect and polarizability
Problem
A caesium atom in its ground state sits between two parallel plates in vacuum. Someone who has just studied the magnetic case argues: "reversing the direction of the applied magnetic field reverses the sign of the magnetic splitting, mlμBB→−mlμBB. By the same logic, reversing the applied electric field from +Ez^ to −Ez^ must reverse the sign of the Stark shift of the ground level."
((a)) Explain, starting from why the ground level has no permanent dipole, why this claim is false for a non-degenerate level such as the caesium ground state.
((b)) State how the induced dipole p behaves when E→−E, and show this is consistent with your answer to (a).