Investigating the temperature dependence of photoelectron spectra in KArn clusters: Insights into stable structures and spectroscopic properties

In this article, we investigate the temperature dependence of the photoelectron spectrum of a potassium atom adsorbed on argon clusters ${\text{Ar}}_n$ (n $=1-10$). We employ a combined Monte Carlo (MC) method with basin-hopping global optimization to simulate the geometries of the argon clusters in the excited 4p state at temperature $T$. Our ab initio model utilizes appropriate pseudopotentials to replace the core electrons of ${\text{K}}^{+}$ and all electrons of the argon atoms, along with core polarization potentials. Electronic energies and transition dipole moments are calculated for each selected geometry, enabling us to simulate the photoelectron spectrum. Our results highlight the significant impact of temperature on the spectral characteristics of photoelectrons emitted from the $K\text{Ar}$ system. At a temperature of 5 K, we observe that the stable structures better reproduce the experimental photoelectron spectra. As the temperature increases, we observe broadening and shifting of the spectral peaks, suggesting the successive evaporation of argon atoms. Additionally, the influence of spin–orbit coupling is examined, which may also affect the spectral features and the dynamics following excitation.