Sommerfeld screening parameters for S1/2terms in X-ray spectra

Abstract

The screening of the nuclear charge by other electrons in the atom is customarily allowed for by introducing two screening parameters sigma 1 and sigma 2 in the Sommerfeld relativistic two-body energy equation. The values of sigma 1 and sigma 2 for the S1/2 levels (L1, M1 etc.), along with probable errors, have been calculated for the atomic number range Z=17 to Z=103. The method used for the calculation involves no series expansion and consequent truncation errors. Also, more precise energy value data have been used for the calculations. It is shown for the first time that the sigma 1 curves for the N6,7 and O2,3 levels cross each other around Z=77, and that, sigma 2>2 for the L1 level and the value of sigma 2 does not increase progressively with n but sigma 2(N1)< sigma 2(M4,5) and sigma 2(O2,3)< sigma 2(N6,7), which necessarily implies that sigma 2(O1)< sigma 2(N6,7). Possible reasons for these new results have been discussed.