Vibronic Fano Resonance in the Intervalence Charge Transfer Band of Mixed-Valence System

Fano resonance has garnered considerable attention due to its wide-ranging applications in physics, chemistry, and materials science. Recent studies show that this interference effect effectively modulates light-matter interactions in the ultraviolet and visible spectral regions. However, achieving Fano resonance at low optical frequencies, particularly in the infrared region, is challenging due to the absence of suitable experimental systems. Here, we present a novel Fano resonance phenomenon involving the interference between electronic and vibrational transitions at closely matched energy positions (infrared region) in a dimolybdenum (Mo₂) mixed-valence system. This complex exhibits a characteristic Fano resonance effect resulting from the interaction between the low-energy, broad intervalence charge transfer (IVCT) band and high-frequency, sharp vibrational bands. This discovery enhances our understanding of Fano resonance and provides valuable insights for future advancements in this emerging field, paving the way for infrared applications.