QUENCHING OF O-2(A(1)DELTA(G)) BY O-2(A(1)DELTA(G)) IN SOLUTION

The reaction in which O-2(a(1) Delta(g)) is quenched by another O-2(a( 1) Delta(g)) molecule is examined in CS2. Spectroscopic data indicate that energy-pooling to form O-2(b(1) Sigma(g)(+)) occurs in this proce ss. This observation is important to the kinetics of O-2(a(1) Delta(g) )-O-2(a(1) Delta(g)) annihilation because O-2(b(1) Sigma(g)(+)) is its elf a precursor of O-2(a(1) Delta(g)). An upper limit of (7.0 +/- 0.8) x 10(5) s(-1) M(-1) is determined for the O-2(a(1) Delta(g))-O-2(a(1) Delta(g)) annihilation rate constant. Data are also presented to indi cate that the quenching of O-2(b(1) Sigma(g)(+)) by the fullerene C-60 is limited by solute diffusion. This result is not consistent with a mechanism of electronic-to-vibrational energy transfer, which thus far has been the only documented deactivation process for O-2(b(1) Sigma( g)(+)) in solution. O-2(b(1) Sigma(g)(+)) quenching by C-60 likely pro ceeds via electronic energy transfer facilitated by the near degenerac y of the O-2(b(1) Sigma(g)(+)) and triplet C-60 energy levels.