We measured the KL0 diagram, and KL1 and KL2 satellite lines in Mg, Al, and Si, ionized by photon excitation, using a high-resolution anti-parallel double-crystal x-ray spectrometer. Their energy values, FWHM, and relative intensities are obtained by the multiple fitting methods and compared with those reported by other excitation processes. It was found that the relative intensity of Mg and Si KL1, and KL2 satellite lines to the KL0 diagram lines depend on the method used to produce the K hole. The evidence of a new transition between Ka3 and Ka4 in Mg, Al, and Si KL1 satellite lines is suggested. These x-ray diagram and satellite lines were investigated theoretically and we found that Mg Ka1;2 diagram lines with hidden satellites are especially in very good agreement with the corresponding experimental ones. Moreover, from the absorption spectra of Mg and Al, the cross sections of the multi-electron transition processes were estimated and match the theoretical values. We also determined the mass attenuation coefficients in a wide energy range covering the K-absorption edge, including a detailed evaluation of the associated uncertainties.