Wavelength match experiment was carried out with a soft X-ray crystal spectrograph for three pumping and absorbing line pairs at wavelengths around 4.5 nm:SiXII3d-2p,4.4021 nm, MgX2s-4p, 4.4050 nm; CuXIX4f-3d, 4.7329 nm, MgX2p-4d, 4.7310 nm and AlXI3p-2s,4.8338 nm and MgIX2s2-2s4p,4.8340 nm.The second line pair was found in this experiment and never appeared in published work. The pros and cons these line pairs for photo-resonant X-ray lasers were compared and discussed.