Lifetimes and quenching cross sections of I2(B 3ΠOu+)

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Abstract
Fluorescence lifetimes, self‐quenching cross sections, and foreign gas quenching cross sections have been measured for I 2 B 3 Π Ou + ) by direct observation of fluorescence decay for excitation in the region 640–499.5 nm, corresponding to excited electronic state levels between v′ ≈ 5 and v′ ≈ 70, close to the dissociation limit. The foreign gas experiments represent the first measurement of foreign gas quenching rates using lifetime methods. A pulsed tunable nitrogen‐laser‐pumped‐dye laser with a linewidth of 0.3 to 0.7 nm and a pulse time of less than 10−8 sec was used as the excitation source. Lifetimes were found to be strongly dependent on v′, varying from less than 0.4 μsec to greater than 7 μsec. Self‐quenching cross sections showed less v′ dependence, varying between 47 and 90 × 10 −16 cm 2 . Foreign gas quenching cross sections were measured for Ar, Br2, CO2, H2, He, Kr, N2, NO, Ne, O2, SF6, and Xe, and showed a dependence on both v′ and the gas used. Values for light gases, such as H2 and He, were typically 1× 10 −16 cm 2 or less, while values for Xe were as high as 23 × 10 −16 cm 2 .