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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >VUV Photodynamics and Chiral Asymmetry in the Photoionization of Gas Phase Alanine Enantiomers
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VUV Photodynamics and Chiral Asymmetry in the Photoionization of Gas Phase Alanine Enantiomers

机译：气相丙氨酸对映体光电离中的VUV光动力学和手性不对称

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摘要

The valence shell photoionization of the simplest proteinaceous chiral amino acid, alanine, is investigated over the vacuum ultraviolet region from its ionization threshold up to 18 eV. Tunable and variable polarization synchrotron radiation was coupled to a double imaging photoelectron/photoion coincidence (i~2PEPICO) spectrometer to produce mass-selected threshold photoelectron spectra and derive the state-selected fragmentation channels. The photoelectron circular dichroism (PECD), an orbital-sensitive, conformer-dependent chiroptical effect, was also recorded at various photon energies and compared to continuum multiple scattering calculations. Two complementary vaporization methodsaerosol thermodesorption and a resistively heated sample oven coupled to an adiabatic expansionwere applied to promote pure enantiomers of alanine into the gas phase, yielding neutral alanine with different internal energy distributions. A comparison of the photoelectron spectroscopy, fragmentation, and dichroism measured for each of the vaporization methods was rationalized in terms of internal energy and conformer populations and supported by theoretical calculations. The analytical potential of the so-called PECD-PICO detection techniquewhere the electron spectroscopy and circular dichroism can be obtained as a function of mass and ion translational energyis underlined and applied to characterize the origin of the various species found in the experimental mass spectra. Finally, the PECD findings are discussed within an astrochemical context, and possible implications regarding the origin of biomolecular asymmetry are identified.
机译：在真空紫外区域，从其电离阈值到18 eV，研究了最简单的蛋白质手性氨基酸丙氨酸的价壳光电离。可调和可变偏振同步加速器辐射耦合到双成像光电子/光子符合（i〜2PEPICO）光谱仪，以产生质量选择的阈值光电子能谱并导出状态选择的碎裂通道。光电子圆二色性（PECD）是一种轨道敏感的，依赖于构象异构体的手性按摩效应，还记录了各种光子能量，并将其与连续多次散射计算进行了比较。两种互补的汽化方法（气溶胶热解吸和结合绝热膨胀的电阻加热样品炉）被用于将丙氨酸的纯对映异构体促进进入气相，产生具有不同内部能量分布的中性丙氨酸。对每种蒸发方法测得的光电子能谱，碎片和二色性的比较在内部能量和构象异构体方面得到了合理化，并得到了理论计算的支持。着重强调了所谓的PECD-PICO检测技术的分析潜力-可以根据质量和离子平移能量获得电子光谱和圆二色性-并用于表征实验中发现的各种物种的起源质谱。最后，在一个天化学背景下讨论了PECD的发现，并确定了有关生物分子不对称性起源的可能含义。

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