Rate data for the relaxation of S(31D2) and S(31S0) by Xe, Ar and He have been obtained using kinetic absorption spectroscopy in the vacuum ultra-violet. The results are discussed, together with data for O(21D2) and O(21S0), in terms of potential curves resulting from the collision between the optically metastable, electronically excited atoms and the noble gases. These considerations are successful in accounting for the relatively high quenching efficiency observed for the 1D2 state, the increase in efficiency with atomic weight of the noble gas and the low efficiencies for quenching of the 1S0 state. A new lower limit is presented for the rate of reaction between S(31D2) and H2. This result is discussed in terms of the potential surfaces available for chemical reaction; the difference in reactivity between S(31D2) and S(31S0) with H2 is accounted for.
