The interpretation of experimental electron momentum distributions (EMDs) of ethanol, one of the simplest molecules having conformers, has confused researchers for years. High-level calculations of Dyson orbital EMDs by thermally averaging the gauche and trans conformers as well as molecular dynamical simulations failed to quantitatively reproduce the experiments for some of the outer valence orbitals. In this work, the valence shell electron binding energy spectrum and EMDs of ethanol are revisited by the high-sensitivity electron momentum spectrometer employing symmetric noncoplanar geometry at an incident energy of 1200 eV plus binding energy, together with a detailed analysis of the influence of vibrational motions on the EMDs for the two conformers employing a harmonic analytical quantum mechanical (HAQM) approach by taking into account all of the vibrational modes. The significant discrepancies between theories and experiments in previous works have now been interpreted quantitatively, indicating that the vibrational effect plays a significant role in reproducing the experimental results, not only through the low-frequency OH and CH torsion modes but also through other high-frequency ones. Rational explanation of experimental momentum profiles provides solid evidence that the trans conformer is slightly more stable than the gauche conformer, in accordance with thermodynamic predictions and other experiments. The case of ethanol demonstrates the significance of considering vibrational effects when performing a conformational study on flexible molecules using electron momentum spectroscopy.

The binuclear homoleptic rhodium carbonyls Rh2(CO)n (n = 8, 7, 6, 5) have been examined theoretically. Three energetically low-lying equilibrium structures of Rh2(CO)8 were found, i.e., one doubly bridged C2v singlet structure and two unbridged singlet structures with D(3d) and D(2d) symmetry. The doubly bridged structure is the global minimum predicted to lie 3.4 kcal/mol below the D(2d) structure and 6.4 kcal/mol below the D(3d) structure. For Rh2(CO)7 the global minimum is either a singlet C2v unbridged structure or a singlet doubly bridged C(s) structure within 1.8 kcal/mol depending upon the theoretical method. For Rh2(CO)6, the global minimum is either a singlet doubly bridged D(2) structure or a singlet unbridged D(2d) structure depending upon the method. Triplet structures for Rh2(CO)7 and Rh2(CO)6 are predicted to be of high energies relative to the low energy singlet structures. For Rh2(CO)5 the C2v singlet singly bridged structure lies below the C2 or C2v triplet structures.

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High-resolution electron energy loss spectroscopy, low-energy electron diffraction, and quadrupole mass spectrometer have been employed to study the effect of atomic hydrogen on the acetylene saturated preadsorbed Si(100)(2×1) surface at room temperature. It is evident that the atomic hydrogen has a strong effect on the adsorbed C2H2 and the change of the underlying surface structure of Si. The experimental results show that CH and CH2 radicals coexist on the Si surface after the dosing of atomic hydrogen; meanwhile, the surface structure changes from Si(2×1) to a dominant of (1×1). These results indicate that the atomic hydrogen can open C=C double bonds and change them into C–C single bonds, transfer the adsorbed C2H2 to C2Hx(x=3,4) and break the underlying Si–Si dimer, but it cannot break the C–C bond intensively. Some C4 species have been formed during the dosing with atomic hydrogen. It may be the result of atomic hydrogen abstraction from C2Hx which leads to carbon catenation between two adjacent CC dimers. The formed C4 is stable on Si(100) surfaces up to 1100 K and can be expected to host diamond nucleation.