Exploration of large amplitude motions in the Ca⁺Ar₂ complex

ABSTRACT

We present a theoretical study of the ground electronic state potential of the Ca⁺Ar₂ complex and of its photoabsorption spectra, simulated at temperatures ranging between 20 and 220 K. These calculations exploit a Monte-Carlo (MC) method, based on a one-electron pseudo-potential approach. A pairwise additive potential fitted to coupled cluster ab initio points, is used to model the Ca⁺Ar₂ complex. Our study shows that the most stable form of Ca⁺Ar₂ is a bent C_2v structure, whereas the linear isomer is located at around 90 ± 10 cm⁻¹ above in energy. The analysis of the photoabsorption spectra establishes that a structural transition from bent Ca⁺Ar₂ to linear ArCa⁺Ar occurs at T∼100 K. Trends in binding energies of both isomers, bond lengths and bond angles are also discussed. Molecular orbital overlaps provide an explanation for the order of stability between the bent and linear structures.

GRAPHICAL ABSTRACT

KEYWORDS:

• Bent Ca⁺Ar₂
• Monte-Carlo computations
• one-electron pseudopotential model
• photoabsorption spectra
• Isomerisation

Acknowledgments

We would like to thank Dr. F. Spiegelman for fruitful discussions. We gratefully acknowledge the support of the COST Action CM1405 entitled MOLIM: Molecules in Motion.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by European Cooperation in Science and Technology [grant number CM1405].