A study has been made of the intensities of the various lines of the neutral helium spectrum, with the particular view of obtaining regularities in the variation of the relative intensities with changes in current density and pressure.
The method used is a modification of that developed by Ornstein at Utrecht. A study has been made of the lines 5876, 5016, 4713, 4472, 4387, 4143, 3964, 3889 and 3819, at pressure of 27,9 and 3 mm., and currents of 64, 20, and 4 milliamperes in a capillary discharge.
The results show little variation with current density except for the trial at 3 mm pressure. At this pressure, the higher members of the series seem to be relatively stronger, and the singlet system is relatively stronger with a decrease in current density.
There is a very definite shift of energy into the higher members of the various series with a decrease in pressure. There does not appear to be much change in relative intensity for the two higher pressures. The singlet system is made more prominent by decreasing the pressure.
Tables are included showing the relative intensities of three members of the diffuse series of the triplet system, 2 members of the principal series of the singlet system and three members of the diffuse series of the singlet system.
