The arc spectra of Cl, Br, and I have been investigated in the region between 2050 and 1230 A. U. Wave-length tables are given. 1396.5 and 1633.6 A. U. are the wave-lengths of the lines of longest wave-length of Cl and Br, respectively, and correspond to the previously known 2062.1 line of I. Doublet differences of 881, 3685, 7600 wave number units are found between lines of Cl, Br, and I spectra respectively and are thought to be the separations of the two levels of normal doublet $p$ states of the atoms. The probable resonance lines are of wave-lengths 1379.6, 1540.8 and 1782.9 A. U. corresponding to radiating potentials of 8.95, 8.01, and 6.92 volts. No band spectrum of HCl appeared in the region investigated although the excitation was probably favorable for its production.

• Received 12 December 1925

DOI:https://doi.org/10.1103/PhysRev.27.397