Ionization potentials of adenine along the internal conversion pathways.

Area of Science:

• Computational Chemistry
• Photochemistry
• Molecular Spectroscopy

Background:

• Adenine's relaxation pathways and excited-state dynamics are crucial for understanding its photophysical behavior.
• Discrepancies exist between experimental and theoretical assignments of adenine's relaxation surface.

Purpose of the Study:

• To compute ionization potentials of adenine in its vertical spectrum and along internal conversion pathways.
• To assess the accuracy of high-level computational methods for these calculations.
• To resolve the long-standing divergence regarding adenine's relaxation surface.

Main Methods:

• High-level ab initio computational methods were employed.
• Calculations covered the vertical electronic spectrum.
• Ionization potentials were computed along key internal conversion pathways.

Main Results:

• Significant ionization energy variations (up to 4.5 eV) were observed between the Franck-Condon region and conical intersections.
• The study provides a detailed assessment of computational method quality.
• Calculations support a revised assignment of adenine's relaxation surface.

Conclusions:

• Computed ionization potentials aid in interpreting experimental data for adenine.
• Findings have broad implications for pump-probe spectroscopy of organic molecules.
• The study offers a guide for future experimental setups and analyses involving adenine and related heterocycles.