Probing the Structures of Neutral B₁₁ and B₁₂ Using High-Resolution Photoelectron Imaging of B₁₁^– and B₁₂^–

Abstract

We report high-resolution photoelectron imaging of B11– and B12– at 354.7 and 532.0 nm, respectively, resolving several low-frequency vibrational modes for neutral B11 and B12. The vibrational information is highly valuable to verify the structures of the neutral clusters. Several isomers are considered, and vibrational frequencies are calculated for B11 and B12 using density functional theory. Comparisons between the experimental and calculated vibrational frequencies prove that the B11 neutral and anion both possess a perfectly planar C2v structure. The B12– anion is quasi-planar with Cs symmetry, while the experiment confirms that neutral B12 possesses C3v symmetry. The high-resolution photoelectron spectra also allow the electron affinities of B11 and B12 to be measured more accurately as 3.401 ± 0.002 and 2.221 ± 0.002 eV, respectively. It is shown that high-resolution photoelectron imaging can be an effective method to determine structures of small neutral boron clusters, complementary to infrared spectroscopy.