The molecular species In2O has been identified in the gas phase as a product of the high temperature reaction between water and indium (850 degrees C) or between indium trioxide (In2O3) and indium (950 degrees C) by the observation of an electronic transition in the near-ultraviolet. The spectra are simplified by supersonic cooling of the sample in a free jet expansion after it is formed. The vibrational structure shows that the molecule has a very similar geometry in the two states involved while the O-18/O-16 isotope shift suggests that the molecule is only slightly nonlinear in the excited electronic state. Rotational structure can be resolved at high resolution and shows an intensity alternation; the molecule thus has a symmetric In-O-In arrangement. (C) 1997 American Institute of Physics.