Ionized strontium is studied by the method of resonant absorption of optical radiation. Because of an accidental frequency overlap, normal rubidium can be used in a lamp as the source of resonant light. Spectral profiles of absorption were made with a scanning Fabry‐Perot interferometer. The 5s½−6p½ line of Rb and the 5s½−5p½ line of Sr+are found to differ by 0.014 Å. Optical and Langmuir probe measurements of density compare favorably. Ion temperatures in a steady‐state and a decaying plasma were determined from the Doppler width. Two different sources of ionized strontium plasma are described. Negative results were obtained in an attempt to optically pump strontium ions in a plasma.