III-M-6 Detection of Metastable Triplet Acetylene Produced by Intersystem Crossing from the Excited A(¹A_u) State

Toshinori SUZUKI, Yang SHI and Hiroshi KOHGUCHI

[J. Chem. Phys. 106, 5292 (1997)]

Triplet metastable species produced by intersystem crossing from the A(¹A_u) state of acetylene has been detected by the sensitized phosphorescence method. A sensitized phosphorescence signal was observed from vibronic levels lying lower than the potential energy barrier for dissociation in the a state suggested previously [N. Hashimoto and T. Suzuki, J. Chem. Phys. 104, 6070 (1996)], but was not observed from levels higher than this barrier. The lifetimes of triplet states produced by intersystem crossing from the V³K¹(J'=2) and V⁴K¹(J'=2) levels were estimated to be 100 and 80 ms.

Figure 1. Laser induced fluorescence (LIF) and sensitized phosphorescence excitation (SPE) spectra simultaneously measured for C₂H₂ in supersonic jet. C₂H₂ was seeded in He, and the flight time from the laser-molecular beam to the sensitized phosphorescence detector was 40 ms.

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