Transmittance signal in real ladder-type atoms

We clarify an interpretation of transmittance signals in ladder-type atomic systems by discriminating the contributions of one-photon resonance, two-photon resonance, and a mixed term of both in the calculated spectra for these ladder-type multilevel atoms. When the two-photon-resonance effect is distinguished from an accurate spectrum calculated by modeling ladder-type electromagnetically-induced transparency for the 5S(1/2) - 5P(3/2) - 5D(5/2) transitions of Rb-87 atoms, we find that the transmittance signals for the 5D(5/2)(F '' = 2,3) states are mainly composed of the mixed term related not to pure-two-photon atomic coherence but to the optical-pumping effect whereas the transmittance signal for the 5D(5/2)(F '' = 4) state originates from both the pure-two-photon-resonance term and the mixed term.