CHOOSING REFERENCE SAMPLES FOR EPR CONCENTRATION MEASUREMENTS .1. GENERAL INTRODUCTION AND SYSTEMS OF S=1 2/

Paramagnetic centers in the reference samples used in electron paramag netic resonance (EPR) spectrometric concentration measurements often d iffer in nature from the centers to be determined in unknowns. Quantit ations based on such an approach can be correct only if the difference s in specific intensities of the two signals, that is, the inequality of the signal areas per paramagnetic particle, is taken into account. This series of papers provides tabulated values that characterize the specific intensities of X-band EPR signals for paramagnetic species of various types in solid samples. The data were obtained by quantum-mec hanical calculations comprising exact diagonalization of the spin Hami ltonian matrices. One can generally use the tabulated values to calcul ate the correction factor when a dissimilar reference sample has to be employed. Examination of this data can also help in selecting a refer ence sample whose paramagnetic centers provide an EPR signal very clos e in specific intensity to the signal of the analyte, no matter how mu ch these two paramagnetic centers differ in nature. With such a refere nce sample, no correction is necessary at all, This first part of the series provides a general introduction and the data for the simplest c lass of paramagnetic species with the effective spin of 1/2.