The optical absorption spectrum of Sr+CO is measured by photofragmentation spectroscopy of mass selected ions. The spectrum, in the energy interval of 19000-23000 cm(-1), shows a regular vibrational structure with peaks separated by approximately 200 cm(-1), plus a low intensity shoulder which covers an energy range up to the dissociation. Electronic configuration interaction calculations reveal the existence of a bistable species with strontium either bonded to the carbon-end or to the oxygen-end of CO in collinear geometries. The assumption that the spectrum depicts excitations from both isomers is examined. (C) 2002 Elsevier Science B.V. All rights reserved.