Photoexcitation and photoejection of an electron bound to a wall by the image potential

We calculate cross sections and transition rates for the photoexcitation and photoejection of an electron initially bound by its image charge to a plane infinite wall, impenetrable to the electron; the electromagnetic wave is incident at an arbitrary angle. The problem reduces to that of a one-dimensional system consisting of an electron bound to a potential -${\mathrm{Ze}}^2$/z for z>0 and ∞ for z≤0 (i.e., a one-dimensional hydrogen atom), with an oscillating electric field parallel to the z axis. Particularly interesting cases include ‘‘murium,’’ a perfectly conducting wall, for which Z=(1/4), and a liquid-helium wall, a case of experimental interest, for which the static dielectric constant is ε=1.057 and Z=(ε-1)/4(ε+1)=0.0069. The dependence of the photoejection cross section on the outgoing energy is the same near threshold as that for photoejection from a real hydrogen atom. This result may seem surprising since neither parity nor angular momentum is conserved.