  Considering the contributions of the main term of the relativistic Coulombian
Green function given by Hostler [J. Math. Phys, 5, 591 (1964)] to the second
order of the S-matrix element and taking into account only the large components
of Dirac spinor of the 2S subshell, we have obtained the imaginary part of the
Rayleigh amplitudes in terms of elementary functions. Thereby, simple and high
accurate formulae for the total cross-sections for photoeffect and pair
production with the electron created in the 2S subshell are obtained via the
optical theorem. Comparing the predictions given by our formulae with the full
relativistic numerical calculations of Kissel et al [Phys. Rev. A 22, 1970
(1980)] and Scofield [LLRL, Internal Report (1973)], a good agreement is found
for low and intermediate Z values if screening effects are taken into account,
for photon energies above the pair production threshold energy. We present our
numerical results for the total photoeffect and pair production cross-sections
for the 2S subshell of Zn and Ag atoms, for various photon energies.
