Theoretical and experimental investigations of the gallium dimeric molecule

Abstract

All-electron ab initio Hartree-Fock (HF), multiconfiguration self-consistent-field (CASSCF), and configuration interaction (Cl) calculations have been carried out to determine the low-lying electronic states of the Ga2 molecule. Six states, bound relative to the 2P ground-term Ga atoms, have been identified in the Cl calculations. The Ga2 molecule has a 3 " electronic ground state, and the next higher lying states are 32¡, l'2g, 'II", * ,, and 2'2g. The calculated vibrational frequency for the 3 " ground state, 175 cm , compares well with the experimental value of 180 cm"1 11. The six lowest lying electronic states have been rationalized in a simple molecular orbital diagram. On the basis of wave functions determined in valence Cl calculations, the oscillator strengths have been computed for selected dipole-allowed transitions. Our calculated transition energies and oscillator strengths compare favorably with the available absorption and emission spectra of Ga2. An approximate treatment of the spin-orbit coupling in the low-lying electronic states of the Ga2 molecule has been carried out. The four lowest lying spin-orbit coupled states, 0¡¡, 0*, lu, 2^, are essentially the split 3 " state. The next higher lying state, 0Í, exhibits a double minimum due to the mixing of the states 32¡ and ' ,. The dissociation energy of the Ga2 molecule has been determined from the high-temperature mass spectrometric data combined with the experimental vibrational frequency and the spin-orbit coupled electronic states from the present work as D'0 = 110.3 ± 7 kJ mol"1.

Why Does a Ga2 Dimer React Spontaneously with H2, but a Ga Atom Does Not?—A Detailed Quantum Chemical Investigation of the Differences in Reactivity Between Ga Atoms and Ga2 Dimers, in Combination with Experimental Results

“…Overall, the value calculated here is in reasonable agreement with the experimental value of 110.8 AE 4.9 kJ mol À1 . [22,23] The calculated relative energies of the electronic states of Ga 2 are in fair agreement with the results of earlier MR-ACPF calculations, [20] [20] GaH possesses a closed-shell ground state (…”

Characterization of Isolated Ga2 Molecules by Resonance Raman Spectroscopy and Variations of GaGa Bonding

“…With the assumption of a Morse potential, the dissociation energy D 0 can be calculated from Equation (3). If zero-point vibrational energy corrections are included, the D e value (upper limit) can be estimated to fall in the range 130-160 kJ mol À1 , comparing satisfactorily with a relatively new gas-phase estimate of about 110 kJ mol À1 [20] and an older estimate of 135 kJ mol…”

“…) according to gas-phase estimates [20] and quantum-chemical calculations. [21] An analysis of the reaction mechanism for the reaction with H 2 has shown, however, that excited states of Ga 2 are involved in the reactions and that the low energy of these excited states is responsible for the reactivity.…”

Systematically Convergent Correlation Consistent Basis Sets for Molecular Core−Valence Correlation Effects: The Third-Row Atoms Gallium through Krypton

“…44, 2007 11387 configuration interaction and a relativistic core potential,87 as well as the atomic spin-orbit splitting from Moore, 88 a SO correction can be "unfolded" from the experimental D 0 value to compare with our theoretical one. Adding these corrections to the experimental D 0 value of Shim80 (26.4 ( 1.7 kcal mol -1 ) gives an estimated experimental D 0 without SO of 28.9 kcal mol -1 . The aCV5Z-DK/awCV5Z-DK values are 30.9 kcal mol -1 after including a shift of -0.2 kcal mol -1 for ZPE, and these values are slightly outside of the experimental error bars.…”