Spectroscopic characterization of Be _2~+ X~2 σ_u~+ and the ionization energy of Be_2

摘要

Rotationally resolved spectra for Be _2~+ have been recorded using the pulsed-field ionization zero kinetic energy photoelectron technique. Vibrational levels in the range ν~+ =0-6 were observed. The rotational selection rules confirmed that the ground state is ~2 σ_u~+, resulting from the removal of an electron from the σ_u antibonding orbital of Be_2. The bond energy and equilibrium distance for Be _2~+ were found to be D _e~+ =16 438 (5) cm~(-1) and R_e~+ =2.211 (8) ?. The ionization energy for Be_2 [59 824 (2) cm~(-1)] was also refined by these measurements. Comparisons with high-level theoretical results indicate that the bonding in Be _2~+ is adequately described by multi reference singles and doubles configuration interaction (MRDCI) calculations that employ moderate to large scale basis sets.