On the electronic structure and spin-orbit coupling of BiB from photoelectron imaging of cryogenically-cooled BiB- anion

We report a study on the electronic structure and chemical bonding of the BiB molecule using high-resolution photoelectron imaging of cryogenically cooled BiB(- )anion. By eliminating all the vibrational hot bands, we can resolve the complicated detachment transitions due to the open-shell nature of BiB and the strong spin-orbit coupling. The electron affinity of BiB is measured to be 2.010(1) eV. The ground state of BiB- is determined to be (2)p(3/2) with a s(2)p(3) valence electron configuration, while the ground state of BiB is found to be S-3(-)(0(+)) with a s(2)p(2) electron configuration. Eight low-lying spin-orbit excited states [S-3(-)(1), (1)?(2), S-1(+)(0(+)), (3)p(2), (3)p(1),( 1)p(1)], including two forbidden transitions, [(3)p(0(-)) and (3)p(0(+))], are observed for BiB as a result of electron detachment from the s and p orbitals of BiB-. The angular distribution information from the photoelectron imaging is found to be critical to distinguish detachment transitions from the s or p orbital for the spectral assignment. This study provides a wealth of information about the low-lying electronic states and spin-orbit coupling of BiB, demonstrating the importance of cryogenic cooling for obtaining well-resolved photoelectron spectra for size-selected clusters produced from a laser vaporization cluster source.

Automated summary

We report a study on the electronic structure and chemical bonding of the BiB molecule using high-resolution photoelectron imaging. By eliminating vibrational hot bands, we resolved the complicated detachment transitions due to the open-shell nature of BiB and the strong spin-orbit coupling. This study provides a wealth of information about the low-lying electronic states and spin-orbit coupling of BiB.