Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA.
J Phys Chem A. 2010 Mar 11;114(9):3190-8. doi: 10.1021/jp909243y.
The fluorescence spectroscopy of Z-phenylvinylacetylene (Z-PVA) has been studied under jet-cooled conditions. The laser-induced fluorescence (LIF) spectrum shows vibronic activity up to 600 cm(-1) above the pi pi* electronic origin at 33 838 cm(-1). In contrast, the single vibronic level fluorescence spectrum of the electronic origin shows strong intensity in transitions ending in ground state levels at least 1200 cm(-1) above the ground state zero-point level. The double-resonance technique of ultraviolet depletion (UVD) spectroscopy was used to show that there are strong absorptions in Z-PVA that are not observed in the LIF spectrum due to the turn of a nonradiative process in this electronic state. The LIF and UVD spectra were compared quantitatively to calculate the relative single vibronic level fluorescence quantum yields. Upon inspection, there are some indications of state specific effects; however, the nature of these effects is unclear. Ab initio and density functional theory calculations of the ground and excited states were used to map the first two excited states of Z-PVA along the C[triple bond]CH bending coordinate, determining them to be pi pi* and pi sigma*, respectively, in character. The crossing of these two states is postulated to be the underlying reason for the observed loss in fluorescence intensity 600 cm(-1) above the pi pi* origin. The spectroscopy of Z-PVA has been compared to the previously characterized E isomer of phenylvinylacetylene [Liu, C. P., Newby, J. J., Muller, C. W., Lee, H. D. and Zwier, T. S. J. Phys. Chem. A 2008, 112 (39), 9454.].
Z-苯乙烯基乙炔（Z-PVA）的荧光光谱在喷射冷却条件下进行了研究。激光诱导荧光（LIF）光谱显示，在 33838cm-1 的ππ电子起源处，振动能级活动高达 600cm-1 以上。相比之下，电子起源的单振子荧光光谱在跃迁中显示出强烈的强度，跃迁结束于基态能级，至少比基态零点水平高 1200cm-1。紫外线耗竭（UVD）光谱的双共振技术用于表明，在 Z-PVA 中有强烈的吸收，由于这个电子态中一个非辐射过程的转变，在 LIF 光谱中没有观察到。LIF 和 UVD 光谱进行了定量比较，以计算相对单振子荧光量子产率。经检查，有一些迹象表明存在状态特异性效应；然而，这些效应的性质尚不清楚。基于对基态和激发态的从头计算和密度泛函理论计算，对 Z-PVA 的前两个激发态沿着 C[三重键]CH 弯曲坐标进行了映射，确定它们分别具有ππ和πσ的特征。这两种状态的交叉被假设为观察到的在ππ起源处上方 600cm-1 处荧光强度损失的根本原因。Z-PVA 的光谱与之前表征的苯基乙烯基乙炔的 E 异构体进行了比较[Liu, C. P., Newby, J. J., Muller, C. W., Lee, H. D. and Zwier, T. S. J. Phys. Chem. A 2008, 112 (39), 9454.]。
