Photoionization spectroscopy of dichromium and dimolybdenum: Ionization potentials and bond energies

Abstract

Photoionization spectroscopy has been used to probe molecular beams of laser-vaporized chromium (Cr2) and molybdenum (Mo2) dimers. Two-color photoionization efficiency spectroscopy has been used to determine the adiabatic ionization potential (IP) of Cr2 and Mo2 to be 56 449±8 cm−1 and 56 042±8 cm−1, respectively. The IP of Cr2 is combined with the IP of Cr [54 575.6±0.3 cm−1, Huber et al., Proc. R. Soc. London, Ser. A 342, 431 (1975)] and the bond energy of Cr2+ [10 200±500 cm−1, Su et al., Chem. Phys. Lett. 201, 199 (1993)] to yield a bond energy of 12 400±500 cm−1 for Cr2. One-color resonant two-photon ionization (R2PI) spectroscopy has been employed to probe the molybdenum dimer molecule in the energy region where its dissociation should occur. The dissociation limit has been ascribed to the threshold observed at 36 100±80 cm−1. This value is combined with the IP of Mo [57 204.3±0.3 cm−1, Rayner et al., J. Opt. Soc. Am. B 4, 900 (1987)] and Mo2 to yield a bond energy of 37 260±80 cm−1 for Mo2+.