The Fluorescence Spectrum of Sodium Vapor in the Vicinity of the D Lines

Excitation of sodium D lines by monochromatic radiation.---When sodium vapor is mixed with hydrogen, air or nitrogen at pressures between 2 and 3 mm it is possible to excite the D lines by radiation in the region 5100 to 5250A. Since this radiation is absorbed only by the sodium molecules it is probable that the primary act is the excitation of the molecule. The excited molecule may then cause the D line emission by collisions of the second kind with atoms, or by dissociating, either spontaneously or as a result of collisions with the foreign gas, into a normal and an excited atom. To distinguish between these processes further experiments are necessary.Conditions governing the appearance of a certain fluorescence band-group in the yellow.---A band-group formerly studied by one of us was found to appear in the yellow region of the fluorescence spectrum under white light stimulation when nitrogen or hydrogen was present at a pressure of 6±{}1 mm and indications are that they are excited by light of their own wave-length. The experiments also verify completely the older work of Wood and Galt on a cathode ray spectrum. Photographs of the absorption spectrum and other considerations indicate that these bands are not the bands ascribed by Barratt and Pringsheim to a sodium-potassium molecule.