Physical mechanism of nonlinear optical properties in Lemniscular carbon nanohoops

Abstract

In this study, the properties of orbital energy levels, one-photon absorption (OPA) spectrum, two-photon absorption (TPA) spectrum, Raman spectrum, pre-resonance Raman spectrum, and electronic circular dichroism (ECD) spectrum of all‑carbon lemniscular nanohoops bis-pm-TC and bis-po-CC were systematically investigated using density functional theory (DFT) and wavefunction analysis. The transition properties of electrons in the excited states were analyzed through charge density difference (CDD) and transition density matrix (TDM) visualization methods, offering insights into the physical mechanisms of intramolecular charge transfer. Additionally, the Raman spectral responses to excitation light of different wavelengths were calculated. The ECD spectrum revealed distinct chiralities for bis-pm-TC and bis-po-CC, which were further explained by analyzing the densities and orientations of their transition electric dipole moments (TEDMs) and magnetic dipole moments (TMDMs).