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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Wavelength-Dependent Photolysis of i-Pentanal and t-Pentanal from 280 to 330 nm
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Wavelength-Dependent Photolysis of i-Pentanal and t-Pentanal from 280 to 330 nm

机译：i-Pentanal和t-Pentanal在280至330 nm范围内的波长依赖性光解

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摘要

Photodissociation of i-pentanal (CH_3)_2CHCH_2CHO; 3-methylbutanal) and t-pentanal ((CH_3)_3CCHO; 2,2-dimethylpropanal) in the 280-330 nm region was investigated at 5 nm intervals by using dye laser photolysis in combination with cavity ring-down spectroscopy. Absorption cross-sections of i-pentanal and t-pentanal were obtained. Both aldehydes exhibited a broad absorption band peaking at 295 nm, with maximum absorption cross-sections of (5.90 +- 0.22) * 10~(-20) and (4.26 +- 0.07) * 10~(-20) cm~2, respectively,for i-pentanal and t-pentanal. The formation yield of the HCO radical from photolysis of i-pentanal and t-pentanal wad determined by monitoring HCO absorption at 613.8 nm. Except for 325 and 330 nm photolysis of i-pentanal, the HCO yield was found to be independent of aldehyde pressure (2-12 Torr) and total pressure (20-400 Torr). For the photodissociation of t-pentanal, the HCO yield was also determined in the 0.5-2 Torr range and was found to increase with t-pentanal pressure. The variation of HCO radical yield with photolysis wavelength was determined. The peak HCO yields from t-pentanal and i-pentanal photolysis were 0.92 +- 0.11 and 0.40 +- 0.08 at 315 nm, respectively, where uncertainty reflects experimental scatter only. The difference in the peak HCO yield from t-pentanal and i-pentanal photolysis was attributed to the opening up of the Norrish II channel for i-pentanal. End products from closed-cell photolysis of i-pentanal and t-pentanal were investigated at 290, 310, and 330 nm by using HPLC. Acetaldehyde was found to be a product from the photodissociation of i-pentanal/N_2 mixtures. Photolysis rates of i-pentanal and t-pentanal to form HCO were calculated for two representative atmospheric conditions (noontime at sea level and 40 deg N latitude on January 1 and on July 1) and were compared to those obtained from acetaldehyde photolysis.
机译：戊醛（CH_3）_2CHCH_2CHO的光解离;通过使用染料激光光解结合腔衰荡光谱技术，以5 nm的间隔研究了280-330 nm区域中的3-甲基丁醛和叔戊醛（（CH_3）_3CCHO; 2,2-二甲基丙醛）。获得异戊醛和叔戊醛的吸收截面。两种醛均在295 nm处出现宽吸收峰，最大吸收截面为（5.90 +-0.22）* 10〜（-20）和（4.26 +-0.07）* 10〜（-20）cm〜2，分别为正戊醛和叔戊醛。通过监测613.8 nm处的HCO吸收来确定i-戊醛和t-戊醛一团光解产生HCO自由基的产率。除了对戊醛的325和330 nm光解作用外，发现HCO的收率与醛压力（2-12 Torr）和总压力（20-400 Torr）无关。对于叔戊醛的光解离，HCO产率也确定在0.5-2 Torr范围内，并发现随叔戊醛压力的增加而增加。确定了HCO自由基产率随光解波长的变化。叔戊醛和异戊醛光解的最高HCO产量在315 nm处分别为0.92±0.11和0.40±0.08，其中不确定度仅反映实验性散射。叔戊醛和异戊醛光解产生的最高HCO产量的差异归因于异戊醛的Norrish II通道的开放。使用HPLC在290、310和330 nm处研究了异戊醛和叔戊醛闭孔光解的最终产物。乙醛被发现是异戊醛/ N_2混合物的光解产物。计算了两种代表性的大气条件（1月1日和7月1日在海平面和北纬40度午间时间）异戊醛和叔戊醛形成HCO的光解速率，并将其与乙醛光解获得的光解速率进行比较。

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