The extension of the X-ray-doublet laws into the field of optics

Abstract

Application of relativity formulas for x-ray doublets to ultra-violet spectra.— Evidence has been presented which indicates that many of the strongest lines in hot spark spectra are due to atoms stripped of all valence electrons excepting the one which in jumping between energy levels emits the radiation. For the L doublets due to atoms with but one L electron, Li(+), Be(2+), B(3+), C(4+), it is found that the frequency difference varies with atomic number Z in accordance with the relativity formula for x-ray doublets Δν=K(Z-s)4, the constant K being.365 for the regular L series, and the screening constant s decreasing from 2.02 for Li(+) to 1.86 for C(4+). Other L doublets are attributed to atoms stripped of all but three L electrons, the same formula holding but giving values of s about 20 per cent greater. In the case of triplets, the frequency differences of the widest pairs give values of s for atoms stripped of all but two or four L electrons which agree well with values for only one, three or five L electrons, though tending to be somewhat greater. Similarly from M doublets and triplets (K=.108) of C and N, values of s were obtained for atoms with from one to three L electrons slightly greater than from the corresponding L lines. In the case of atoms with only one M electron, the values of s decrease from 7.45 for Na(+) to 5.74 for P(5+), corresponding values of s from N, O and P series of doublets being slightly larger; for atoms with only two M electrons (widest pair of triplets) and with only three M electrons (doublets) the values of s vary up to about 9. For doublets corresponding to outer transitions 3d2-3d1, 4d2-4d1 and 4f2-4f1 the values of s come out close to 10. In the case of irregular L and M doublets corresponding to transitions from the 2s and 3s levels, the law for corresponding x-ray doublets also holds, the differences (sqrt[νs]-sqrt[νp]) increasing regularly and not very greatly with Z. All these facts are shown to agree well with what should be expected according to the Bohr-Sommerfeld theory; and the values of s give quantitatively the influence upon the effective nuclear charge of the addition of electrons in the valence shells. New series terms. The above relations enable the value of s for a given series for a given ionized atom to be predicted, and led to the discovery of an L doublet at λ1240 due to N(5+), and to the assignment of the following L doublets: λ990 to N(3+), λ1493 and 1744 to N(+), λ789 and λ658 to O(4+), and λ922 to O(2+). These results give us a new method of predicting spectra and of determining the state of ionization of atoms emitting certain lines. Doublet frequency differences in extreme ultra-violet for 2p2-2p1 terms due to B(3+) and C(4+) were measured by use of a special grating giving up to ten orders.

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