Self-absorption and the effect of exciting voltage on the soft X-ray emission edge of Li and other light metals

The soft X-ray K-emission edges of Li and Be, L23-emission edges of Na, Mg and Al and the M-emission edge of K have been recorded using electron excitation with accelerating voltages varying from 0·2 to 6·0 kV. Progressive changes in the observed edge shapes are observed which can be satisfactorily explained in terms of differing self-absorption thickness at the different voltages. Data recorded at different accelerating voltages can be used to calculate absorption coefficients and correct for self-absorption. The corrected curves agree with those recorded at low voltage and in particular it is confirmed that the sharp edge in the Li K spectrum is not due to self-absorption.