Allowed and forbidden transitions in an atom placed near an ideally conducting cylinder

The properties of dipole-allowed and -forbidden (quadrupole) transitions in an atom placed near an ideally conducting cylinder are considered. Explicit analytical expressions for transition rates for different orientations of dipole and quadrupole are found. It is shown that the decay rates of dipole and quadrupole transitions with radially oriented moments tend to infinity when the cylinder radius tends to zero. On the ether hand, for tangential orientation (phi orientation), the dipole transition rate decreases while the quadrupole transition rate increases substantially. As a result, the quadrupole decay rates may approach the dipole decay rates. Such behavior has analogy in neither spherical nor plane geometry of the metal interface.