After what year was the " Z " number known as a physical characteristic of atoms ?
formula_1 where : formula_2 is the frequency of the main or K x-ray emission line formula_3 and formula_4 are constants that depend on the type of line For example , the values for formula_3 and formula_4 are the same for all formula_7 lines ( in Siegbahn notation ) , so the formula can be rewritten thus : formula_8 ( Hz ) Moseley himself chose to show this without formula_3 per se , which instead was given by Moseley as a pure constant number in the standard Rydberg style , as simply 3/4 ( that is , 1 - 1/4 ) of the fundamental Rydberg frequency ( 3.29*1015 Hz ) for K - alpha lines , and ( again ) for L - alpha lines according to the Rydberg formula , where formula_3 must be 1/4 - 1/9 = 5/36 times the Rydberg frequency ; this also was the way Moseley chose to write it .