Abstract
Data taken from spectrograms using a vacuum spark containing red phosphorus supplemented by spectrograms previously described have enabled a complete revision and extension of the spectra of P III, P IV, and P V. Certain quintet terms in P II have also been located. In P III nineteen new terms have been found which classify fifty-nine lines. Six of these terms replace previous terms which have proved erroneous. The ionization potential is found to be 30.012±0.003 volts. Tentative intercombinations between the doublet and quartet systems are given. In P IV twenty-three new terms have been found which classify fifty-one lines. Several intercombinations have been located between the singlet and triplet systems. The various series are badly perturbed. The ionization potential is 51.106±0.013 volts. In P V fourteen new terms have been located which classify twenty lines. The series are very regular and give an ionization potential of 64.698±0.003 volts. The previous data have been entirely revised in view of new measurements and complete term tables as well as complete lists of lines now classified in the Schumann region are given.