@misc{9246159,
  abstract     = {{Carbon dioxide and argon can form hydrated clusters in water-rich environments, and their photoionization dynamics are of fundamental interest in atmospheric and astrochemistry. In this work, we combine photoelectron–photoion coincidence (PEPICO) detection with velocity map imaging (VMI) using 21.22 eV vacuum ultraviolet light from a helium discharge lamp to investigate the photoionization of ($CO_2)_m$, $Ar_m$, and $(Ar_m\cdot H_2O)$ clusters. A theoretical transfer-matrix model of the VMI spectrometer is carried out, and numerical simulations are performed to optimize the electrode configuration. Python-based software has been developed for coincidence-event filtering, false-coincidence suppression, and Abel inversion. Our Monte Carlo study of popular Abel inversion methods (pBasex and rBasex) indicates that the rBasex method is more robust and is therefore used in our data analysis.

Our experiments reveal several key findings. For both $Ar_m$ and $(CO_2)_m$ clusters, we observe a clear solvation effect: the measured binding energy decreases with increasing cluster size, showing the strong dependence of interactions on the local cluster environment. We quantified the delocalization effect of a homogeneous cluster ion, and to the best of our knowledge, this is the first experimental evidence of this effect in an argon cluster. For hydrated argon clusters, we observe a large ionization-core signal across all cluster ions, which might suggest evaporative dissociation from large cluster core or a strong polarization effect induced by the water molecule. Our data cannot distinguish between these two possibilities. For $(CO_2)_m$ clusters, our qualitative results suggest possible atomic rearrangement processes associated with the $B^{2}\Sigma_{u}^{+} \text{ and } A^{2}\Pi_{u}$ ionization states, which warrant further investigation.

These results show that combining photoelectron photoion coincidence spectroscopy with VMI is effective for probing cluster dynamics. The observed size-dependent binding energies and charge delocalization mechanism provide benchmark data for theoretical models of weakly bound clusters.}},
  author       = {{Liu, Tao}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Study of hydrated argon and carbon dioxide cluster using Velocity Map Imaging}},
  year         = {{2026}},
}