Two-photon circular-linear dichroism of perylene in solution: a theoretical-experimental study

Area of Science:

• Photophysics and Spectroscopy
• Quantum Chemistry
• Materials Science

Background:

• Two-photon absorption (TPA) is a non-linear optical process crucial for materials characterization.
• Understanding excited state properties requires advanced spectroscopic techniques.
• Perylene, a rigid and centrosymmetric molecule, serves as a model system for studying photophysical phenomena.

Purpose of the Study:

• To theoretically and experimentally analyze the TPA and TPCLD spectra of perylene in solution.
• To demonstrate the utility of TPCLD in elucidating excited state symmetry and transition dipole moments.
• To showcase TPCLD's potential in uncovering spectral features masked by dominant TPA transitions.

Main Methods:

• Experimental measurements using the open-aperture Z-scan technique with a femtosecond amplified system.
• Theoretical calculations employing time-dependent density functional theory (TD-DFT) at the B3LYP/aug-cc-pVDZ level.
• Inclusion of solvent effects using the polarizable continuum model (PCM).

Main Results:

• A three-energy-level diagram aids in determining transition electric dipole moments and their angles for TPA.
• TPCLD successfully reveals excited state symmetry and the angles of transition electric dipole moments relative to the ground state.
• The study explains how TPCLD can identify spectral features obscured in conventional TPA spectroscopy.

Conclusions:

• TPCLD offers unique insights into photophysical properties not accessible by linear or standard TPA spectroscopy.
• The combined theoretical-experimental approach provides a comprehensive understanding of perylene's spectral characteristics.
• TPCLD is a powerful tool for characterizing complex molecular systems and advanced materials.