Vibrationally Resolved Photoelectron Spectroscopy and Quantum Chemical Calculations of InCn– (n = 3–10) Clusters

The vibrationally resolved photoelectron spectra of InC_n^- (n = 3-10) clusters were measured using size-selected anion photoelectron spectroscopy. The structures of InC_n^-/0 (n = 3-10) clusters were investigated through quantum chemical calculations. A pronounced odd-even alternation in vertical detachment energies (VDEs) of InC_n^- (n = 3-10) is observed as the carbon chain length increases. The InC_n^- (n = 4, 6, 8, and 10) anions exhibit higher VDEs than their adjacent anions with odd carbon numbers. The most stable structures of InC_n^- and InC_n (n = 3-10) adopt C_∞v symmetric linear structures with the indium atom located at the end of the carbon chain, except for InC₁₀. InC₁₀ exhibits a C₁₀ ring structure with the indium atom bonding externally to one carbon atom, which is slightly more stable than the linear structure. Bonding analysis reveals the monovalent nature of the indium atom and the covalent character of the In-C bond. Finally, the limitations of the CCSD(T) method in achieving high-accuracy calculations for this system are discussed.