Electronic spectroscopy of (N2O) n + ( n = 2–6): Competition between the charge resonance and charge transfer bands

A hemibond (two-center three-electron bond), formed by a charge resonance interaction, is a characteristic structural motif in radical cation clusters. Hemibonded clusters exhibit strong absorption in the UV-visible region, which is attributed to the charge resonance (CR) transition and serves as a marker band for hemibond formation. Despite its significance, how microsolvation affects the CR transition of the hemibonded ion core remains unclear. In this study, we performed electronic spectroscopy for (N2O)n+ (n = 2-6) clusters containing the hemibonded (N2O)2+ ion core to elucidate the microsolvation effect via clustering of N2O molecules. In the observed spectra, a charge transfer (CT) transition was detected in addition to the CR transition for n = 3. Our results reveal that the CR and CT transitions predominantly lead to the formation of N2O+ and (N2O)2+ fragments, respectively. As microsolvation proceeds, the CR band appears to exhibit a significant red shift. This is attributed to the contribution of the CT excitation to the N2O+ fragment channel via the thermal dissociation pathway.