Supersonic metal cluster beams of refractory metals: Spectral investigations of ultracold Mo2

来自 AIP Publishing

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102

作者：

Hopkins，B J.

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摘要：

A novel technique involving pulsed laser vaporization of the bulk metal within a pulsed supersonic nozzle has been shown to successfully produce ultracold bare metal clusters of even the most refractory of metals, tungsten and molybdenum. Clusters of up to 25 atoms may be readily prepared using this technique. Mass‐selective resonant two‐photon ionization spectra of Mo2produced in this fashion show that the dimer is efficiently cooled in the expansionTtrans<6 K,Trot∼5 K, andTvib∼325 K. We have rotationally resolved theA1Σ+u←X1Σ+g(0–0) band for92Mo2and determined the bond length in the ground and excited states to be 1.940±0.009 and 1.937±0.008 Å, respectively. This confirms and extends the analysis of Efremovet al.[J. Mol. Spectrosc.73, 40 (1970)] who prepared98Mo2by flash photolysis of isotopically pure Mo(CO)6. We have also observed the (1–1), (2–2), and (3–3) sequence bands which together with the ground state data of Efremovet al.determine vibrational constants ω′e=449.0±0.2 cm−1and ωex′e=2.3±0.2 cm−1for theA1Σ+ustate. The lifetime of theA1Σ+uv=0 state of Mo2has been measured to be 18±3 ns by time‐delayed two‐photon ionization. The ionization potential of Mo2is found to be less than 6.42 eV (compared to 7.10 eV for atomic Mo) indicating a substantially stronger chemical bond in Mo+2than in Mo2. A discussion of the electronic structure of Mo2and the implications of these findings for bonding in other transition metal dimers is also presented.

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关键词：

atomic and molecular physics molybdenum bond lengths electronic structure evaporation molecular structure atomic beams dimers laser radiation molecules