Structure and Fluxionality of B13+ Probed by Infrared Photodissociation Spectroscopy

Abstract

We use cryogenic ion vibrational spectroscopy to characterize the structure and fluxionality of the magic number boron cluster B₁₃⁺ . The infrared photodissociation (IRPD) spectrum of the D₂ -tagged all-¹¹ B isotopologue of B₁₃⁺ is reported in the spectral range from 435 to 1790 cm^-1 and unambiguously assigned to a planar boron double wheel structure based on a comparison to simulated IR spectra of low energy isomers from density-functional-theory (DFT) computations. Born-Oppenheimer DFT molecular dynamics simulations show that B₁₃⁺ exhibits internal quasi-rotation already at 100 K. Vibrational spectra derived from these simulations allow extracting the first spectroscopic evidence from the IRPD spectrum for the exceptional fluxionality of B₁₃⁺ .

Keywords: anharmonic effects; boron clusters; infrared photodissociation spectroscopy; internal rotation; molecular dynamics simulations.