[en] The computer programme HEX (a modification of programme REX) is a nonlinear, least squares, matrix minimization code for evaluation of Si(Li) detector X-ray spectra induced by charged particle bombardment. Correction to the Gaussian areas to allow for low energy tailing of peaks and secondary fluorescence has been included in the calculation. For our detector, this correction is largest (9%) for phosphorous and decreases with X-ray to less than 1% for copper. Since our present range of energies observed extends from 0.6-40 keV, absorption errors are usually large for the softer X-rays. Inclusion of L X-ray line intensities (down to 0.897 keV, Z = 28) into the fitting process allows for evaluation of absorption. In addition, the amount of absorption correction for sodium in air particulate field samples (where particle size effects dominate) has been assessed by comparison with results from the proton scattering (PESA) method. (orig.)