Brouard M, Cireasa R, Clark A P, Groenenboom G C, Hancock G, Horrocks S J, Quadrini F, Ritchie G A D, Vallance C
The Physical and Theoretical Chemistry Laboratory, The Department of Chemistry, University of Oxford, Oxford OX1 3QZ, United Kingdom.
J Chem Phys. 2006 Oct 7;125(13):133308. doi: 10.1063/1.2210009.
Polarized laser photolysis, coupled with resonantly enhanced multiphoton ionization detection of O(1D2) and velocity-map ion imaging, has been used to investigate the photodissociation dynamics of ozone at 193 nm. The use of multiple pump and probe laser polarization geometries and probe transitions has enabled a comprehensive characterization of the angular momentum polarization of the O(1D2) photofragments, in addition to providing high-resolution information about their speed and angular distributions. Images obtained at the probe laser wavelength of around 205 nm indicate dissociation primarily via the Hartley band, involving absorption to, and diabatic dissociation on, the B 1B2(3 1A1) potential energy surface. Rather different O(1D2) speed and electronic angular momentum spatial distributions are observed at 193 nm, suggesting that the dominant excitation at these photon energies is to a state of different symmetry from that giving rise to the Hartley band and also indicating the participation of at least one other state in the dissociation process. Evidence for a contribution from absorption into the tail of the Hartley band at 193 nm is also presented. A particularly surprising result is the observation of nonzero, albeit small values for all three rank K = 1 orientation moments of the angular momentum distribution. The polarization results obtained at 193 and 205 nm, together with those observed previously at longer wavelengths, are interpreted using an analysis of the long range quadrupole-quadrupole interaction between the O(1D2) and O2(1Deltag) species.
偏振激光光解结合对O(¹D₂)的共振增强多光子电离检测和速度映射离子成像，已被用于研究193nm波长下臭氧的光解离动力学。使用多种泵浦和探测激光偏振几何结构以及探测跃迁，除了能提供有关O(¹D₂)光碎片速度和角分布的高分辨率信息外，还能全面表征其角动量偏振。在约205nm探测激光波长下获得的图像表明，解离主要通过哈特利带进行，涉及到B¹B₂(³¹A₁)势能面上的吸收和非绝热解离。在193nm处观察到相当不同的O(¹D₂)速度和电子角动量空间分布，这表明在这些光子能量下的主要激发是到与产生哈特利带的状态具有不同对称性的状态，并且还表明至少有另一个状态参与了解离过程。还给出了在193nm处吸收进入哈特利带尾部的贡献证据。一个特别令人惊讶的结果是观察到角动量分布的所有三个秩K = 1取向矩均为非零值，尽管数值很小。利用对O(¹D₂)和O₂(¹Δg)物种之间长程四极 - 四极相互作用的分析，解释了在193nm和205nm处获得的偏振结果，以及之前在更长波长处观察到的结果。
