Photofragment imaging of Cr2+: Bond energies for Cr2+ and Cr2

The chromium dimer cation produced and cooled in a supersonic expansion was investigated with mass-selected ion photofragment imaging. Photodissociation experiments at 532 and 559 nm produce significant kinetic energy release in the atomic cation fragment, whose analysis leads to a bond dissociation energy for Cr2+ of 1.35 ± 0.12 eV (31.1 ± 2.8 kcal/mol). Combination of this with the ionization energies of Cr2 and Cr leads to a new determination for the bond energy of neutral Cr2 of 1.58 ± 0.12 eV (36.4 ± 2.8 kcal/mol). Although this diatomic is claimed to have a “sextuple” bond, the bond energy is confirmed to be relatively low, which has been attributed in the past to ineffective overlap of d orbitals.