Vacuum UV fluorescences from ionic rare‐gas alkali excimer molecules were observed by electron beam excitation. A gas mixture of xenon or krypton with a hot vapor of rubidium was excited to obtain a diffuse emission band centered at 164 nm from (XeRb)+and 133 nm from (KrRb)+molecular ions. The observed emission bands are assigned to the 21&Sgr;+→11&Sgr;+transition of (XeRb)+and (KrRb)+, respectively.