Pulsed-field ionization zero electron kinetic energy spectrum of the ground electronic state of BeOBe⁺

The ground electronic state of BeOBe⁺ was probed using the pulsed-field ionization zero electron kinetic energy photoelectron technique. Spectra were rotationally resolved and transitions to the zero-point level, the symmetric stretch fundamental and first two bending vibrational levels were observed. The rotational state symmetry selection rules confirm that the ground electronic state of the cation is ²σ_g⁺. Detachment of an electron from the HOMO of neutral BeOBe results in little change in the vibrational or rotational constants, indicating that this orbital is nonbonding in nature. The ionization energy of BeOBe [65480(4) cm ^-1] was refined over previous measurements. Results from recent theoretical calculations for BeOBe⁺ (multireference configuration interaction) were found to be in good agreement with the experimental data.