Resonances in Electron Scattering on Benzisoxazole

Area of Science:

• Physical Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Benzisoxazole's electronic structure and potential resonance states are not fully understood.
• Investigating temporary anion states provides insights into molecular interactions and reaction pathways.

Purpose of the Study:

• To identify and characterize anionic resonances in benzisoxazole using electron energy loss spectra (EELS).
• To elucidate the decay mechanisms of these resonances and the role of the dipole-bound anion.
• To compare the resonance behavior of benzisoxazole with its isomer, benzoxazole.

Main Methods:

• Electron energy loss spectroscopy (EELS) was employed to probe benzisoxazole.
• Equation-of-motion coupled-cluster theory calculations were performed.
• Non-Hermitian theory with a complex absorbing potential was utilized to stabilize temporary anion states.

Main Results:

• EELS revealed anionic resonances near 1.2 eV and 2.2 eV, with another likely below 0.5 eV.
• Resonances decay via vibrational excitation or electron emission, influenced by vibronic couplings and a dipole-bound anion.
• Theoretical calculations predicted three π* scattering resonances (π₁^*, π₂^*, π₃^*) below 3 eV, consistent with experimental findings.
• Benzisoxazole's dipole-bound anion and resonance decay dynamics distinguish it from benzoxazole.

Conclusions:

• The study confirms the existence of stable dipole-bound and metastable π* resonance states in benzisoxazole.
• The dipole-bound anion plays a significant role in the resonance decay mechanisms.
• Benzisoxazole exhibits unique resonance characteristics compared to benzoxazole, attributed to its dipole moment and anion state.