  The proton radioactivity half-lives of spherical proton emitters are
investigated theoretically. The potential barriers preventing the emission of
protons are determined in the quasimolecular shape path within a generalized
liquid drop model (GLDM) including the proximity effects between nuclei in a
neck and the mass and charge asymmetry. The penetrability is calculated with
the WKB approximation. The spectroscopic factor has been taken into account in
half-life calculation, which is obtained by employing the relativistic mean
field (RMF) theory combined with the BCS method with the force NL3. The
half-lives within the GLDM are compared with the experimental data and other
theoretical values. The GLDM works quite well for spherical proton emitters
when the spectroscopic factors are considered, indicating the necessity of
introducing the spectroscopic factor and the success of the GLDM for proton
emission. Finally, we present two formulas for proton emission half-life
calculation similar to the Viola-Seaborg formulas and Royer's formulas of alpha
decay.
