Aguirre F, Pratt S T
Argonne National Laboratory, Argonne, Illinois 60439, USA.
J Chem Phys. 2004 Nov 22;121(20):9855-64. doi: 10.1063/1.1810511.
The photoionization and photodissociation dynamics of H(2) and D(2) in selected rovibrational levels of the B (1)Sigma(u) (+) and C (1)Pi(u) states have been investigated by velocity map ion imaging. The selected rotational levels of the B (1)Sigma(u) (+) and C (1)Pi(u) states are prepared by three-photon excitation from the ground state. The absorption of fourth photon results in photoionization to produce H(2)(+) X (2)Sigma(g)(+) or photodissociation to produce a ground-state H(1s) atom and an excited H atom with n >or= 2. The H(2) (+) ion can be photodissociated by absorption of a fifth photon. The resulting H(+) or D(+) ion images provide information on the vibrational state dependence of the photodissociation angular distribution of the molecular ion. The excited H(n >or= 2) atoms produced by the neutral dissociation process can also be ionized by the absorption of a fifth photon. The resulting ion images provide insight into the excited state branching ratios and angular distributions of the neutral photodissociation process. While the experimental ion images contain information on both the ionic and neutral processes, these can be separated based on constraints imposed on the fragment translational energies. The angular distribution of the rings in the ion images indicates that the neutral dissociation of molecular hydrogen and its isotopes is quite complex, and involves coupling to both doubly excited electronic states and the dissociation continua of singly excited Rydberg states.
通过速度成像技术，研究了处于B(1)Σu(+)和C(1)Πu态特定振转能级的H₂和D₂的光电离及光解离动力学。B(1)Σu(+)和C(1)Πu态的特定转动能级由基态经三光子激发制备。吸收第四个光子会导致光电离产生H₂(+) X(2)Σg(+)，或光解离产生基态H(1s)原子和n≥2的激发态H原子。H₂(+)离子可通过吸收第五个光子而光解离。由此产生的H(+)或D(+)离子图像提供了关于分子离子光解离角分布的振动状态依赖性的信息。中性解离过程产生的激发态H(n≥2)原子也可通过吸收第五个光子而被电离。由此产生的离子图像有助于深入了解中性光解离过程的激发态分支比和角分布。虽然实验离子图像包含了离子和中性过程的信息，但基于对碎片平动能施加的限制，可以将它们分开。离子图像中环的角分布表明，分子氢及其同位素的中性解离相当复杂，涉及到与双激发电子态和单激发里德堡态的解离连续体的耦合。
