EXCITATION OF O-2(A DELTA-1G, B SIGMA-1G+) AND I(P-2(1/2) BY ENERGY-TRANSFER FROM I-2(A,A' 3-PI-1,2U) IN SOLID RARE-GASES

O2a1Δg, b1Σg+ → X 3Σg- and I 2P 1 2→2P 3 4 fluorescence occurs in I2/O2-doped rare gas matrices when I2 is excited with visible laser light. O2(a1Δg) and I(2P 1 2) are populated independently by near-resonant energy transfer from the metastable triplet states of I2. The doublet splitting of the O2a→X band, which peaks at 7879 and 7863 cm-1 in argon, is interpreted as sensitized emission from O2 trapped in distinct nearest neighbour positions of the donor 3I2. Annealing reverses the intensity of the doublet, showing that the sites can be interconverted. It is suggested that the a→X emission rate is enhanced by the sensitizer, causing a lifetime reduction of the a1Δg state from 79 s in pure argon to 21 and 3±1 s next to I2. The long-lived O2(a1Δg) state is the precursor of I2-sensitized emission from O2(b1Σg+). The lifetime of O2(b1Σg+) is reduced from 24.5 ms in pure argon to 17±1 ms in the presence of I2. © 1990.