Theoretical determination of the electronic ground state of the MgC molecule
ABSTRACT Results of generalized valence bond (GVB) plus configuratiuon
interaction (CI) calculations for the potential curves and spectroscopic
constants of the two lowest lying electronic states of the MgC molecule
are presented. The (3)Sigma- state was found to be the ground
state but with the (5)Sigma- state lying very close above.
The small difference in energy and the similarity of the rotational and
vibrational spectroscopic constants must be carefully taken into account
in any experimental search for the MgC molecule.
- SourceAvailable from: Vladimir E Bondybey[Show abstract] [Hide abstract]
ABSTRACT: Having closed valence sub-shells, the alkaline earth atoms participate in covalent bonding via orbital hybridization and exchange interactions, with additional contributions from dispersion interactions. Starting from a closed ns2 configuration imparts different characteristics to the chemistry of this group, as compared to metals that have open-shell atomic ground states. Theoretical studies of the bonding of the Group IIA metals have been pursued for many years, and they are known to be challenging for ab initio electronic structure methods. The bonding motifs have been examined, and the differences between beryllium and the remainder of the group explored. Experimental studies that probe the bonding, particularly for beryllium, have lagged behind the theoretical work. In the present Letter we describe our recent spectroscopic and theoretical investigations of simple beryllium compounds, and discuss these results in terms of their relationship to the properties of the heavier Group IIA elements.Chemical Physics Letters 01/2011; 506(1):1-14. · 2.15 Impact Factor
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ABSTRACT: Electronic spectra for BeC have been recorded over the range 30 500-40 000 cm(-1). Laser ablation and jet-cooling techniques were used to obtain rotationally resolved data. The vibronic structure consists of a series of bands with erratic energy spacings. Two-color photoionization threshold measurements were used to show that the majority of these features originated from the ground state zero-point level. The rotational structures were consistent with the bands of (3)Π-X(3)Σ(-) transitions. Theoretical calculations indicate that the erratic vibronic structure results from strong interactions between the four lowest energy (3)Π states. Adiabatic potential energy curves were obtained from dynamically weighted MRCI calculations. Diabatic potentials and coupling matrix elements were then reconstructed from these results, and used to compute the vibronic energy levels for the four interacting (3)Π states. The predictions were sufficiently close to the observed structure to permit partial assignment of the spectra. Bands originating from the low-lying 1(5)Σ(-) state were also identified, yielding a (5)Σ(-) to X(3)Σ(-) energy interval of 2302 ± 80 cm(-1) and molecular constants for the 1(5)Π state. The ionization energy of BeC was found to be 70 779(40) cm(-1).The Journal of Chemical Physics 12/2012; 137(21):214313. · 3.12 Impact Factor
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ABSTRACT: The linear MgC(3)(-) anion has been identified in the products from the dual Nd:YAG laser ablation of carbon and magnesium rods trapped in solid Ar at ∼12 K. Measurements of (13)C isotopic shifts confirm the identification of the ν(1)(σ) vibrational fundamental at 1797.5 cm(-1). A second fundamental ν(2)(σ) has been tentatively identified at 1190.1 cm(-1). The results are in good agreement with the predictions of density functional theory calculations using the B3LYP functional with the 6-311+G(d) basis set. This is the first optical detection of the linear isomer of MgC(3)(-).The Journal of Chemical Physics 08/2011; 135(5):054513. · 3.12 Impact Factor