SAVITZKY AND GOLAY DIFFERENTIATION IN AES

For the analysis of Auger electron spectra it is popular and very usef ul to differentiate the acquired direct spectra numerically by Savitzk y and Golay's method to provide peaks whose peak-to-peak height may be measured. To compare data recorded at different channel separations, epsilon (number of eV per channel), it is important to be able to assi gn an energy equivalent, E(D), to the differentiating function which i s independent of epsilon. It is shown that the adoption of 2m epsilon for the differential width, where 2m + 1 is the number of points in th e Savitzky and Golay function, leads to errors and inconsistencies. It is recommended that (2m + 1)epsilon be identified with E(D). To obtai n E(D) values intermediate between those possible with Savitzky and Go lay's method, a modified function is developed with added +/-(m + 1)th terms. The strength of these terms is between 0 and +/-(m + 1)/N, whe re N is the normalisation constant, and the exact value is roughly in proportion to the fractional excess of E(D) in the interval between th e values permitted in Savitzky and Golay's original approach. An accur ate assessment is made for the value to be used for E(D) values mid-wa y between those usually obtained by Savitzky and Golay's method.