Vibrationally resolved photoelectron spectroscopy of BO- and BO2-:: A joint experimental and theoretical study

We report a photoelectron spectroscopy and computational study of two simple boron oxide species: BO- and BO2-. Vibrationally resolved photoelectron spectra are obtained at several photon energies (355, 266, 193, and 157 nm) for the B-10 isotopomers, (BO-)-B-10 and (BO2-)-B-10. In the spectra of (BO-)-B-10, we observe transitions to the (2)Sigma(+) ground state and the (2)Pi excited state of (BO)-B-10 at an excitation energy of 2.96 eV. The electron affinity of (BO)-B-10 is measured to be 2.510 +/- 0.015 eV. The vibrational frequencies of the ground states of (BO-)-B-10 and (BO)-B-10 and the (2)Pi excited state are measured to be 1725 +/- 40, 1935 +/- 30, and 1320 +/- 40 cm(-1), respectively. For (BO2-)-B-10, we observe transitions to the (2)Pi(g) ground state and two excited states of (BO2)-B-10, (2)Pi(u), and (2)Sigma(+)(u), at excitation energies of 2.26 and 3.04 eV, respectively. The electron affinity of (BO2)-B-10 is measured to be 4.46 +/- 0.03 eV and the symmetrical stretching vibrational frequency of the (2)Pi(u) excited state of (BO2)-B-10 is measured to be 980 +/- 30 cm(-1). Both density functional and ab initio calculations are performed to elucidate the electronic structure and chemical bonding of the two boron oxide molecules. Comparisons with the isoelectronic AlO- and AlO2- species and the closely related molecules CO, N-2, CN-, and CO2 are also discussed.