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Melding quantum and classical mechanics is an abiding quest of physical chemists who strive for heuristic insights and useful tools. We present a surprisingly simple and accurate treatment of ground-state two-electron atoms. It makes use of only the dimensional dependence of a hydrogen atom, together with the exactly known first-order perturbation value of the electron-electron interaction, both quintessentially quantum, and the D → ∞ limit, entirely classical. The result is an analytic formula for D-dimensional two-electron atoms with Z ≥ 2. For D = 3 helium, it gives accuracy better than 2 millihartrees, which is better than current density functional theory. A kindred explicit formula for correlation energy exploits interpolation between D → ∞ and D = 1 or 2; when added to the Hartree-Fock energy, it improves accuracy for D = 3 helium to better than 0.1 millihartrees.

Numerous branch features in the (0,0) [12.0] Ω=2←X 3Δ3 and (0,0) [13.1] Φ43←X 3Δ3 band systems of the iron monocarbide, FeC, have been studied using optical Stark spectroscopy. The electric field induced splittings in the high resolution laser induced fluorescence spectra were analyzed to produce values for the permanent electric dipole moments, μ, of 4.02(6) D, 4.44(6) D, and 2.36(3) D for the [12.0] Ω=2, [13.1] Φ43, and X 3Δ3 states, respectively. A comparison with other iron containing molecules and theoretical predictions is made.

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The [18.1]1∏←X 1∑+ band system of a molecular beam sample of RuC has been recorded field free and in the presence of a static electric field using high resolution laser induced fluorescence spectroscopy. The Stark shifts of the optical features for the 102RuC isotopomer were analyzed to produce permanent electric dipole moments of 3.31(4) and 4.09(14) D for the [18.1]1∏ and X 1∑+ states, respectively. The hyperfine structure associated with spectral features for the 101RuC and 99RuC isotopomers was analyzed to produce electric quadrupole and magnetic hyperfine coupling parameters. The hyperfine structure and dipole moments are interpreted using a molecular orbital correlation model and compared with predictions from electronic structure calculations and isovalent iron monocarbide, FeC.