Electronic structure of the calcium monohydroxide radical

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Molecular Spectroscopy

Background:

• The calcium hydroxide (CaOH) radical is a molecule of interest in various chemical and physical processes.
• Understanding its electronic states is crucial for predicting its behavior and reactivity.
• Previous studies have provided some data, but a comprehensive mapping of its electronic structure, especially excited states, is lacking.

Purpose of the Study:

• To computationally determine the three-dimensional potential energy surfaces for the 12 lowest electronic states of the CaOH radical.
• To investigate the nature of nonlinear and quasilinear excited states, including Renner-Teller couplings and state mixings.
• To provide accurate excitation energies, spectroscopic constants, dipole moments, and oscillator strengths for these states.

Main Methods:

• Employed effective valence shell Hamiltonian (H(v)) calculations.
• Mapped three-dimensional potential energy surfaces for multiple electronic states.
• Focused on basis set characteristics for high-accuracy computations.

Main Results:

• Generated potential energy surfaces for the 12 lowest electronic states of CaOH.
• Identified nonlinear local minima in the F (2)Pi and G (2)Pi states due to an avoided crossing.
• Calculated previously unavailable data, including excited state dipole moments and oscillator strengths, and compared with experimental and prior computational data.

Conclusions:

• The study successfully mapped the electronic states of CaOH, providing valuable data for future research.
• The findings clarify the complex nature of excited states, including nonlinear geometries and couplings.
• The research highlights the importance of specific basis sets for achieving high accuracy in CaOH radical calculations.