State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, China.
J Chem Phys. 2011 Feb 14;134(6):064301. doi: 10.1063/1.3554213.
We report a tunable vacuum ultraviolet photodissociation study of H(2)O from different unstable resonances in the B̃(1)A(1) electronic state, using the H-atom Rydberg tagging technique. The quantum state resolved OH product translational energy distributions and angular distributions have been measured. Experimental results illustrate, for the first time, that excitation to the different unstable resonances has very different effect on the OH(X) and OH(A) product channels. The OH(X) product rotational distributions vary only slightly, while the OH(A) product rotational distributions and state-resolved angular distributions change dramatically as the photolysis energy increases. Effect of parent rotational excitation on the OH(A) product has also been observed. Through careful simulations to the experimental spectra, OH(A)∕OH(X) branching ratios have been determined at five photolysis wavelengths. The general agreement between theory and experiment in the branching ratios is good. The branching ratios for the OH(A) product from different parent rotational levels are close to the nuclear spin-statistics value, which is also consistent with the extremely low rotational temperature of the H(2)O beam in the current experiment.
我们报告了使用 H 原子里德堡标记技术对 B̃(1)A(1)电子态中不同不稳定共振态的 H(2)O 进行可调谐真空紫外光解的研究。测量了 OH 产物的量子态分辨平移能分布和角分布。实验结果首次表明，激发到不同的不稳定共振态对 OH(X)和 OH(A)产物通道有非常不同的影响。OH(X)产物的转动分布变化很小，而 OH(A)产物的转动分布和量子态分辨角分布随着光解能量的增加而显著变化。还观察到母体转动激发对 OH(A)产物的影响。通过对实验光谱的仔细模拟，在五个光解波长处确定了 OH(A)/OH(X)分支比。理论与实验在分支比上的一般一致性很好。来自不同母体转动能级的 OH(A)产物的分支比接近核自旋统计值，这也与当前实验中 H(2)O 束的极低转动温度一致。
