Photoredox laser chemistry of transition metal oxides

We describe two-color laser excitation of tungsten oxide in ambient air to effect a fully reversible photoredox cycle. One color is infrared, apparently functioning as heat, and the other is visible or shorter wavelength, but not necessarily super bandgap, apparently supplying electronic excitation. In the case of either tungsten oxide or molybdenum oxide, the process can be monitored using a very strong set of Raman spectroscopic features. This process could find application in optical data storage and may be a generally useful strategy for manipulating transition metal oxides.