[en] We derive an approximation for transition moments between excited states consistent with the approximations and assumptions normally used to obtain transition moments between the ground and excited states in the random-phase approximation and its higher-order approximations. We apply the result to the calculation of the photoionization cross sections of the 2 ³S and 2 ¹S metastable states of helium by a numerical analytical continuation of the frequency-depentdent polarizability. The procedure completely avoids the need for continuum basis functions. The cross sections agree well with the results of other calculations. We also predict an accurate two-photon decay rate for the 2 ¹S metastable state of helium. The entire procedure is immediately applicable to several problems involving photoionization of metastable states of molecules