“…This gives a gas-kinetic collision rate at 300 K which is the upper limit for the rate of recombination of CF30 with F, equal to 1.7 X 1011 L mol"1 s"1. The value found for fe3, which is 4-5 times smaller than this, suggests that a modest orientational requirement exists for the collision to be reactive, similar to (but less restrictive than) that observed in the recombination of CF3 radicals.15 Introduction Photochemical solar energy conversion is an important and highly active area of research.2'14 Much attention has been focussed upon the photosensitized reduction (by an electron relay, R) of methyl viologen, MV2+, since the oxidized relay, Rox, can be regenerated by a suitable electron donor, D, and since reduced methyl viologen, MV+-, in the presence of a suitable catalyst is reoxidized to MV2+ with concurrent water splitting MV H2 Y catalyst (1) MV* HzO Hydrogen is, therefore, photogenerated from water at the expense of a sacrificial donor (eq 1).…”