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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Time-resolved EPR study of singlet oxygen in the gas phase
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Time-resolved EPR study of singlet oxygen in the gas phase

机译：气相中单线态氧的时间分辨EPR研究

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X-band EPR spectra of singlet O_2(~1Δ _g) and triplet O_2(~3Σ_g -) were observed in the gas phase under low molecular-oxygen pressures P_(O2) = 0.175-0.625 Torr, T = 293-323 K. O_2(~ 1Δ_g) was produced by quenching of photogenerated triplet sensitizers naphthalene C_8H_(10), perdeuterated naphthalene, and perfluoronaphthalene in the gas phase. The EPR spectrum of O_2(~1Δ_g) was also observed under microwave discharge. Integrated intensities and line widths of individual components of the EPR spectrum of O_2(~3Σ_g ~-) were used as internal standards for estimating the concentration of O _2 species and P_(O2) in the EPR cavity. Time-resolved (TR) EPR experiments of C_8H_(10) were the main focus of this Article. Pulsed irradiation of C_8H_(10) in the presence of O_2(~3Σ_g ~-) allowed us to determine the kinetics of formation and decay for each of the four components of the O_2(~1Δ_g) EPR signal, which lasted for only a few seconds. We found that the kinetics of EPR-component decay fit nicely to a biexponential kinetics law. The TR EPR 2D spectrum of the third component of the O_2(~1Δ_g) EPR spectrum was examined in experiments using C_8H_(10). This spectrum vividly presents the time evolution of an EPR component. The largest EPR signal and the longest lifetime of O_2(~1Δ_g), τ = 0.4 s, were observed at medium pressure P_(O2) = 0.4 Torr, T = 293 K. The mechanism of O_2(~1Δ_g) decay in the presence of photosensitizers is discussed. EPR spectra of O _2(~1Δ_g) evidence that the spin-rotational states of O_2(~1Δ_g) are populated according to Boltzmann distribution in the studied time range of 10-100 ms. We believe that this is the first report dealing with the dependence of O_2(~1Δ_g) EPR line width on P_(O2) and T.
机译：在低分子氧压力P_（O2）= 0.175-0.625 Torr，T = 293-323 K下，在气相中观察到单重态O_2（〜1Δ_g）和三重态O_2（〜3Σ_g-）的X带EPR谱。通过在气相中淬灭光生三重态敏化剂萘C_8H_（10），氘化萘和全氟萘来产生O_2（〜1Δ_g）。在微波放电下也观察到O_2（〜1Δ_g）的EPR谱。 O_2（〜3Σ_g〜-）的EPR谱中各个成分的积分强度和线宽被用作估算EPR腔中O _2种类和P_（O2）浓度的内标。 C_8H_（10）的时间分辨（TR）EPR实验是本文的重点。在O_2（〜3Σ_g〜-）存在下对C_8H_（10）进行脉冲辐照使我们能够确定O_2（〜1Δ_g）EPR信号四个分量中每一个的形成和衰减动力学，这种信号仅持续了几个秒。我们发现，EPR组分衰减的动力学很好地符合双指数动力学定律。使用C_8H_（10）在实验中检查了O_2（〜1Δ_g）EPR光谱的第三部分的TR EPR 2D光谱。该频谱生动地呈现了EPR组件的时间演变。在中压P_（O2）= 0.4 Torr，T = 293 K时，观察到最大的EPR信号和最长的O_2（〜1Δ_g）寿命，τ= 0.4 s。存在时O_2（〜1Δ_g）衰减的机理讨论了光敏剂的种类。 O _2（〜1Δ_g）的EPR谱表明，在研究的10-100 ms的时间范围内，O_2（〜1Δ_g）的自旋旋转状态根据玻耳兹曼分布分布。我们认为这是处理O_2（〜1Δ_g）EPR线宽对P_（O2）和T的依赖性的第一份报告。

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