Effects of donor/acceptor strengths on the multiphoton absorption: an EOM-CCSD correction vector study

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Organic pi-conjugated systems are crucial in materials science.
• Accurate calculation of multiphoton absorption (MPA) spectra is essential for designing new materials.
• Existing methods may not fully capture the nuances of MPA in these systems.

Purpose of the Study:

• To develop and apply a novel correction method (CV) for calculating MPA spectra.
• To investigate the influence of substituent effects (donor/acceptor strengths) on MPA.
• To compare results from ab initio and semiempirical calculations.

Main Methods:

• Equation of Motion Coupled-Cluster method with Single and Double excitations (EOM-CCSD).
• Development of a correction method (CV) for MPA spectra.
• Ab initio and semiempirical Intermediate Neglect of Differential Overlap (INDO) Hamiltonian calculations.

Main Results:

• The CV method accurately calculates single- and MPA spectra.
• Electron-donating and electron-withdrawing substituents enhance both two- and three-photon absorption cross sections.
• Enhancement is more pronounced for two-photon absorption compared to three-photon absorption.
• Ab initio calculations yield higher excitation energies and lower MPA cross sections than semiempirical INDO.

Conclusions:

• The developed CV method is effective for MPA spectral calculations.
• Substituent effects significantly modulate MPA properties in stilbene derivatives.
• Computational level (ab initio vs. semiempirical) impacts predicted MPA cross sections.