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Updated: Jun 8, 2026

Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
Published on: August 6, 2018
Quantum state-selected photodissociation dynamics of H2O: two-photon dissociation via the C̃ electronic state
Kaijun Yuan1, Yuan Cheng, Lina Cheng
1State key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China.
Abstract:
The photodissociation dynamics of H(2)O via the C̃ state by two-photon excitation has been investigated using the H atom Rydberg tagging time-of-flight technique. The rotational resolved action spectrum of the C̃←X̃ transition band has been measured. The line widths show a pronounced dependence on the parent rotational excitation in the C̃ state. The quantum state resolved OH product translational energy distributions and angular distributions have also been obtained. By carefully simulating these distributions, quantum state distributions of the OH product as well as the state-resolved angular anisotropy parameters were determined. The experimental results confirm the variation of two competitive predissociation pathways. A heterogeneous predissociation channel is mediated by rotational coupling to the B̃ (1)A(1) state associated with the a-axis (k(a)(')), and a homogeneous pathway arises from purely electronic coupling to the à (1)B(1) state. We have also obtained the branching ratios of the OH(X) and OH(A) products, and related these to the C̃→à and C̃→B̃ pathways. The branching ratios display a strong k(a)(') dependence.
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The electrons of the outermost energy level determine the energetic stability of the atom and its tendency to form chemical bonds with other atoms. The innermost electron shell has a maximum capacity of two electrons, but the next two electron shells can each have a maximum of eight electrons. This is known as the octet rule, which states that, with the exception of the innermost shell, atoms are most stable energetically when they have eight electrons in their valence shell, the...

