When Polanyi moved to the University of Toronto, his first graduate students were looking for enhanced reaction rates with vibrationally excited hydrogen, as well as looking for the presence of vibrationally excited hydrogen chloride during the exothermic reaction of molecular chlorine with atomic hydrogen. Graduate student Kenneth Cashion was working with Polanyi when they made their first discoveries about chemiluminescence, the light emitted by an atom molecule when it is in an excited state. This work was first published in 1958.