Watching Vibrations Steer Electrons: Ultrafast Vibration-Induced Absorption Switching through Real-Time Orbital Modulation in a Confined Quantum System

Abstract

Excess electrons (EEs), transient anionic species pivotal in radiation chemistry, catalysis, and optoelectronics, have long been stabilized via solvent interactions such as hydrogen bonding in water or polar solvent traps. While these systems enable electron localization, their environmental sensitivity, limited spectral tunability, and static confinement mechanisms restrict applications requiring dynamic control. Here, we introduce a solvent-free paradigm using a supramolecular electropositive cage (C₆₀F₆₀) to confine and strongly couple an electron with a triatomic CO₂ molecule, bypassing traditional solvation limitations. Through ab initio molecular dynamics, we uncover CO₂’s dual role as a nonlinear quantum actuator: Its bending vibration (∠_OCO = 122–156°) steers sub-50 fs electron oscillation via synchronized s/p-orbital hybridization and polarity switching. Crucially, this vibration-EE coupling modulates the EE-orbital’s symmetry, switching Laporte-forbidden (∠_OCO < 133°/UV-dark) to allowed (∠_OCO ≈ 133–140°/invisible-light and ∠_OCO > 140°/visible-light) transitions, thereby enabling vibration-induced absorption switching spanning 380–760 nm. The C₆₀F₆₀ cage enhances CO₂’s electron affinity by 6.1 eV through noncovalent electrostatic stabilization, creating a vibrationally active yet chemically inert environment, a stark contrast to solvent-dependent systems. This platform reveals ultrafast coherence between molecular vibrations and electron redistribution, establishing a dynamic quantum confinement model in which mechanical motion directly dictates optical responses. By bridging triatomic molecular dynamics to macroscopic tunable luminescence, this work advances the design of stimuli-responsive optoelectronic materials, offering applications in wavelength-adaptive scintillators and ultrafast optical switches while redefining the role of vibrations in quantum state manipulation.