Fluorne Arc of Low-Current Strength and Its Optical Spectrum

A pure fluorine dc arc is operated in an Al2O3 tube. At each end of the tube a pair of tungsten electrodes is connected with the tube via copper cascades. The main tube is fed with a permanent flow of fluorine while the electrodes are protected from the same by separate argon flows. At the constricted red column of a fluorine arc at 10 A the spectrum was recorded end-on. It consists essentially of the affinity continuum of atomic fluorine which extends from 360 nm to shorter wavelengths and a large number of atomic fluorine lines emitted above 600 nm. In addition, a diffuse molecular fluorine arc was found which emits especially strong F+2 bands between 420 and 460 nm. At the discharge the properties of hot fluorine will be determined.