A Weisskopf–Wigner theory has been used to investigate the spontaneous emission of a two-level atom placed in a photon superfluidity.
It is found that the atom decays exponentially.
However, the atomic decay rate changes periodically with its position.
It gets the minimum when atom is located at the wave nodes.
The largest decay rate of the atom in photon superfluidity has the same order of magnitude as it is in vacuum of free space.