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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Luminescence and Raman Spectra of Acetylacetone at Low Temperatures
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Luminescence and Raman Spectra of Acetylacetone at Low Temperatures

机译：乙酰丙酮的低温发光和拉曼光谱

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摘要

Raman spectra of acetylacetone were recorded for molecules isolated in an argon matrix at 10 K and for a polycrystalline sample. In the solid sample, broad bands appear superimposed on a much weaker Raman spectrum corresponding mainly to the stable enol form. The position of these bands depends on the excitation wavelength (514.5 and 488.8 nm argon ion laser lines were used), sample temperature, and cooling history. They are attributed to transitions from an excited electronic state to various isomer states in the ground electronic state. Laser photons have energies comparable to energies of a number of excited triplet states predicted for a free acetylacetone molecule (Chen, X.-B.; Fang, W.-H.; Phillips, D. L. J. Phys. Chem. A 2006, 110, 4434). Since singlet-to-triplet photon absorption transitions are forbidden, states existing in the solid have mixed singlet/triplet character. Their decay results in population of different isomer states, which except for the lowest isomers SYN enol, TS2 enol (described in Matanovic I.; Doslic, N. J. Phys. Chem. A 2005, 709, 4185), and the keto form, which can be detected in the Raman spectra of the solid, are not vibrationally resolved. Differential scanning calorimetry detected two signals upon cooling of acetylacetone, one at 229 K and one at 217 K, while upon heating, they appear at 254 and 225 K. The phase change at higher temperature is attributed to a freezing/melting transition, while the one at lower temperature seems to correspond to freezing/ melting of keto domains, as suggested by Johnson et al. (Johnson, M. R.; Jones, N. H.; Geis, A; Horsewill. A. J.; Trommsdorff, H. P. J. Chem. Phys. 2002, 116, 5694). Using matrix isolation in argon, the vibrational spectrum of acetylacetone at 10 K was recorded. Strong bands at 1602 and 1629 cm~(-1) are assigned as the SYN enol bands, while a weaker underlying band at 1687 cm~(-1) and a medium shoulder at 1617 cm~(-1) are assigned as TS2 enol bands.
机译：记录了在10 K氩气基质中分离的分子和多晶样品的乙酰丙酮拉曼光谱。在固体样品中，宽带出现在弱得多的拉曼光谱上，主要对应于稳定的烯醇形式。这些带的位置取决于激发波长（使用了514.5和488.8 nm的氩离子激光线），样品温度和冷却历史。它们归因于从激发电子态到基态电子态的各种异构体态的转变。激光光子的能量可与为游离乙酰丙酮分子预测的许多激发三重态的能量相当（Chen，X.-B .; Fang，W.-H .; Phillips，DLJ Phys.Chem.A 2006，110，4434 ）。由于禁止单重态到三重态的光子吸收跃迁，因此固体中存在的状态具有混合的单重态/三重态特征。它们的衰变导致不同异构体状态的种群，除了最低异构体SYN烯醇，TS2烯醇（描述于Matanovic I.; Doslic，NJ Phys。Chem。A 2005，709，4185）和酮形式，它们可以在固体的拉曼光谱中被检测到，没有被振动解析。差示扫描量热法在冷却乙酰丙酮时检测到两个信号，一个在229 K时出现，一个在217 K时出现，在加热时它们出现在254和225 K处。高温下的相变归因于冻结/融化转变，而如Johnson等人所提出的，一个在较低温度下似乎与酮结构域的冻结/融化相对应。 （Johnson，M.R。; Jones，N.H。; Geis，A; Horstwill.A.J。; Trommsdorff，H.P.J.Chem.Phys.2002，116，5694）。使用氩气中的基质分离，记录了10 K下乙酰丙酮的振动光谱。将1602和1629 cm〜（-1）处的强带指定为SYN烯醇带，将1687 cm〜（-1）处较弱的下层带和1617 cm〜（-1）的中等肩带指定为TS2烯醇带。乐队。

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