Photochemistry of Acetylene at 193.3 nm

Article abstract of DOI:10.1021/j100122a018

The quantum yield (QY) of diacetylene in the 193.3 nm photolysis of acetylene has been measured as a function of pressure, decomposition, and added gases.The QY of diacetylene is near unity (0.9 +/-0.1) when the decomposition is 1percent or less.The QY of C2H2 + hν -> C2H + H is 0.3 +/- 0.1, which is determined by the C2HD yield from the photolysis of C2H2 + C2D6 (or D2) mixtures.The yields is in good agreement with the QY of H atoms photodissociated from C2H2; C2H reacts with C2H2 to produce an equivalent amount of diacetylene.The remaining 60-70percent diacetylene arises from the metastable acetylen (C2H2**) reacting with ground-state acetylene at 193.3 nm and above 0.1 Torr of acetylene.The quenching of diacetylene formed via C2H2** by various foreign gases at various wavelengths is compared.The quenching order at 193.3 nm is N2 < D2 < H2 < C2D6 < n-C4H10.It is postulated that an adduct from C2H2** + C2H2 is initially formed before it dissociates into C2H4 + H2 or C2H + C2H3.Yields of C4H2, C2HD, and C2H2 were measured by FT-IR calibrated with pure samples.The C4H2 yield at 193 nm does not change with addition of N2 up to 600 Torr.The absorption cross section of C2H2 has been measured in the 190 - 230-nm region.The production of C4H2 was examined at wavelength below and above the dissociation threshold.The metastable acetylene reactions may be important in haze formation in Titan's atmosphere.

Full text of DOI:10.1021/j100122a018

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Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.