Chemisorption of oxygen on Al and Mg was found to cause photon emission with a probability of about ${10}^{-7\mathrm{}}$ per molecule. The photon intensity was continuously recorded for oxygen exposures ${10}^{-8\mathrm{}}$-${10}^{-1\mathrm{}}$ Torr sec. The intensity is closely related to the chemisorption rate and a rate ${<10\mathrm{}}^{-3\mathrm{}}$ monolayer/sec was easily detected. Spectral analysis revealed broad emission bands with maxima at 5100 and 5900 Å for Al + ${\mathrm{O}}_2$ and at 4700 and 5600 Å for Mg + ${\mathrm{O}}_2$.

• Received 25 March 1974

DOI:https://doi.org/10.1103/PhysRevLett.32.1114