Infrared spectrum of the disilane cation (Si2H6+) from Ar-tagging spectroscopy

Abstract

The infrared spectrum of the disilane cation, Si₂H₆⁺, in its ²A_1g ground state is inferred from photodissociation of cold Si₂H₆⁺–Ar_n complexes (n = 1, 2). Vibrational analysis is consistent with a D_3d symmetric structure of H₃SiSiH₃⁺ generated by ionization from the bonding σ_SiSi orbital. Structural, vibrational, and electronic properties of Si₂H₆⁽⁺⁾ and Si₂H₆⁺–Ar_1,2 are determined at the MP2/aug-cc-pVTZ and B3LYP/aug-cc-pVTZ levels. Ar ligands bind weakly at the C₃ axis on opposite sides to Si₂H₆⁺ with only a minor impact on the Si₂H₆⁺ properties. The calculations reveal a low-energy H₂SiHSiH₃⁺ isomer with C_s symmetry and a Si–H–Si bridge, which is only ∼15 kJ mol⁻¹ above the D_3d structure.