PRODUCT DISTRIBUTIONS OF THE C2H2+O AND HCCO+H REACTIONS - RATE-CONSTANT OF CH2(X)OVER-TILDE 3B1) + H
PRODUCT DISTRIBUTIONS OF THE C2H2+O AND HCCO+H REACTIONS - RATE-CONSTANT OF CH2(X)OVER-TILDE 3B1) + H
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DOI：
10.1021/j100203a043
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发表时间：
1992-11-26
影响因子：
--
通讯作者：
PEETERS, J
中科院分区：
文献类型：
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作者：
BOULLART, W;PEETERS, J
在285 K下测定了C_2H_2/O/H体系中两种主要亚甲基源C_2H_2 + O ->（CH_2（B_1））-B-3 + CO（r2 a）或HCCO + H（r2 B）和HCCO + H -> CH_2（1A_1）+ CO（r3 a）或（CH_2（B_1））-B-3 + CO（r3 B）的支化比。使用放电流/分子束质谱技术（D-F/MBMS）。在用0.5托的甲烷取代25%的氦浴ps时，其选择性地清除CH 2（1A 1）;在不存在CH 4的情况下，单线态CH 2主要碰撞转化为（CH 2（B1））-B-3。以这种方式，获得单线态和三线态CH 2的总形成速率的比率。由于反应r3的mte与反应r2 b的速率通过HCCO与H反应的已知分数相关联，与0竞争，因此比率k2 a/k2 b和k3 a/k3 b都可以从数据中提取。因此，也包括可能的系统误差，发现C2 H2 + 0的HCCO产率为k2 b/k2 = 85（-9）+4%，HCCO + H的CH 2（1A 1）产率为k3 a/k3 = 92 +/-15%（95%置信区间）。此外，从不同[H]/[O]比下的CH 2信号，相对于已知的（k（CH 2 +O））-C-3，推导出（CH 2（B1））-B-3 + H --> CH（2 PI）+ H-2（r1）的速率常数：k1 =（1.6 +/-0.6）× 10（14）cm 3 Mol-1 S-1。
The branching ratios of the two dominant methylene sources in C2H2/O/H systems C2H2 + O --> (CH2(B1))-B-3 + CO (r2a) or HCCO + H (r2b) and HCCO + H --> CH2(1A1) + CO (r3a) or (CH2(B1))-B-3 + CO (r3b) have been determined, at 285 K, using discharge-flow/molecular beam mass spectrometry techniques (D-F/MBMS). The ratios were derived from the observed decrease of MBMS CH2 signals Upon substituting 25% of the helium bath ps by 0.5 Torr of methane, which selectively scavenges CH2(1A1); in the absence of CH4 the singlet CH2 is mainly collisionally converted to (CH2(B1))-B-3. In this way, the ratios of the total formation rates of singlet and triplet CH2 are obtained. As the mte of reaction r3 is linked to the rate of reaction r2b by the known fraction of HCCO reacting with H, in competition with 0, both the ratios k2a/k2b and k3a/k3b can be extracted from the data. Thus, including also probably systematic errors, the HCCO yield of C2H2 + 0 is found to be k2b/k2 = 85(-9)+4% and the CH2(1A1) yield of HCCO + H, k3a/k3 = 92 +/- 15% (95% confidence intervals). In addition, the rate constant of (CH2(B1))-B-3 + H --> CH(2PI) + H-2 (rl) was derived relative to the known (k(CH2+O))-C-3 from CH2 signals at different [H]/[O] ratios:k1 = (1.6 +/- 0.6) X 10(14) cm3 Mol-1 S-1.