Lepelmeier Jörn, Titze Katharina, Kartouzian Aras, Boesl Ulrich, Heiz Ulrich
Technische Universität München, Lehrstuhl für Physikalische Chemie, Lichtenbergstr. 4, 85748, Garching, Germany.
Chemphyschem. 2016 Dec 15;17(24):4052-4058. doi: 10.1002/cphc.201600811. Epub 2016 Nov 3.
UV spectroscopy and electronic circular dichroism (ECD) experiments on supersonic-beam-cooled deuterated (R)-(+)-3-methylcyclopentanone ([D ]-(R)-(+)-3-MCP) have been performed by using a laser mass spectrometer. The spectral resolution not only allowed excitation and CD measurements for single vibronic transitions but also for the rotational P, Q, and R branches of these transitions. The investigated n→π*18042501 transition showed the largest anisotropy factor ever observed for chiral molecules in the gas phase, which, due to residual saturation of the excited transition, represents only a lower limit for the real anisotropy factor. Furthermore, one-color (1+1+1) and two-color (1+1') resonance-enhanced multiphoton ionization (REMPI) measurements were performed and the effusive-beam (room temperature) and supersonic-beam results for [D ]-(R)-(+)-3-MCP were compared. These results allowed a differentiation between single-step ECD (comparable to conventional ECD) and cumulative ECD (only possible in multiphoton excitation) under supersonic-beam conditions.
利用激光质谱仪对超声速束冷却的氘代（R）-（+）-3-甲基环戊酮（[D]-（R）-（+）-3-MCP）进行了紫外光谱和电子圆二色性（ECD）实验。光谱分辨率不仅允许对单个振动电子跃迁进行激发和圆二色性测量，还允许对这些跃迁的转动P、Q和R支进行测量。所研究的n→π*18042501跃迁显示出气相中手性分子所观察到的最大各向异性因子，由于激发跃迁的残余饱和，这仅代表实际各向异性因子的下限。此外，进行了单色（1+1+1）和双色（1+1'）共振增强多光子电离（REMPI）测量，并比较了[D]-（R）-（+）-3-MCP的喷流束（室温）和超声速束结果。这些结果使得在超声速束条件下能够区分单步ECD（类似于传统ECD）和累积ECD（仅在多光子激发中可能）。
