Long-wave arc spectra of alkalis and alkaline earths

New types of photographic plates sensitive to red and infrared radiation are employed to record the emission spectra of electric arcs containing alkalis or alkaline earths.Several lines characteristic of sodium, potassium, rubidium, and cesium are observed in the interval 8,500 to 11,800 A. A larger number of lines are measured in calcium, strontium, and barium spectra between the limits 6,500 and 11,300 A. Practically all of the observed lines are accounted for as com- binations of identified spectral terms.A new system of band heads, presumably due to CaO, was found in the infrared.