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Prompt and delayed dissociation dynamics of dicationic HCN induced by electron impact
Xingyu Guo1, Enliang Wang1, Wenchao Zhao1
1Hefei National Research Center for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China.
The Journal of Chemical Physics
|July 9, 2025
Summary
Doubly ionized hydrogen cyanide (HCN2+) dissociation was studied using electron impact. Two pathways were observed, with delayed fragmentation suggesting unique vibrational state populations compared to photon ionization.
Area of Science:
- Physical Chemistry
- Atomic and Molecular Physics
- Chemical Physics
Background:
- Doubly ionized hydrogen cyanide (HCN2+) is a molecular ion relevant to understanding fragmentation dynamics.
- Investigating dissociation pathways provides insight into molecular ion stability and reaction mechanisms.
Purpose of the Study:
- To investigate the dissociation mechanisms of doubly ionized hydrogen cyanide (HCN2+) produced by electron beam impact.
- To compare the fragmentation dynamics of HCN2+ induced by electron impact versus photon impact.
Main Methods:
- Utilized a coincidence ion imaging spectrometer to analyze dissociation products.
- Measured time-of-flight spectra to distinguish between prompt and delayed fragmentation.
- Calculated potential energy surfaces and employed reaction rate theory.
Main Results:
- Identified two distinct dissociation mechanisms: prompt decomposition and delayed fragmentation.
- Observed that the deprotonation channel (HCN2+ → H+ + CN+) originates from low-lying electronic states.
- Found significantly longer metastable state lifetimes for electron-induced ionization compared to photon-induced processes.
Conclusions:
- Electron impact produces HCN2+ with different vibrational state populations than photon impact.
- Discrepancies in metastable state lifetimes are attributed to these population differences.
- Potential energy surface calculations support the observed fragmentation dynamics.
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