Valence electronic structures of CH2BrCl and CF2BrCl: binding energy spectra and electron momentum distributions.

The binding energy spectra (BES) of valence shells of CH2BrCl and CF2BrCl have been measured at a series of different azimuthal angles by an (e, 2e) electron momentum spectrometer employing noncoplanar symmetric geometry at an impact energy of 1200 eV plus binding energy. The experimental momentum profiles (XMPs) are extracted from the sequential BES and compared with the theoretical ones calculated by using Hartree-Fock (HF) and density functional theory (DFT-B3LYP) calculations with 6-311G, 6-311++G**, and aug-cc-pVTZ basis sets. In general, the DFT-B3LYP calculations using the larger basis sets 6-311++G** and aug-cc-pVTZ describe the XMPs well for both molecules. Moreover, the pole strengths of main ionizations from the inner valence orbitals 2a', 3a', and 1a' of CH2BrCl are determined, and the controversial ordering of two outer valence orbitals 3a' ' and 6a' of CF2BrCl has also been assigned unambiguously.

Optical oscillator strengths for valence-shell and Br-3d inner-shell excitations of HCl and HBr.

Absolute optical oscillator strength density spectra for valence-shell excitations of HCl and HBr, as well as for Br-3d inner-shell excitations of HBr, have been determined by high-resolution electron-energy-loss-spectroscopy method in the dipole limit. Absolute optical oscillator strengths for the discrete transitions of HCl and HBr are reported and compared with the previous results determined by the photoabsorption method.

High resolution electron momentum spectroscopy of dichlorodifluoromethane: unambiguous assignments of outer valence molecular orbitals.

On account of controversial orbital assignment that appeared in previous works, [J. Chem. Phys. 120, 7933 (2004), and references therein] high resolution electron momentum spectroscopy (EMS) measurements on dichlorodifluoromethane has been carried out using a newly developed high resolution energy-momentum dispersive multichannel spectrometer employing asymmetric noncoplanar geometry at an impact energy of 2500 eV plus binding energy. Four resolved structures and two shoulders were obviously observed in high resolution binding energy spectrum in energy range covering eight outermost valence orbitals, whereas only two broad lobes were resolved in previous EMS studies [J. Chem. Phys. 120, 7933 (2004); Chin. Phys. 14, 2467 (2005)]. The ordering of these orbitals was reassigned unambiguously by simple comparison of experimental momentum distributions with theoretical ones.

Electron-impact excitation of D1delta <-- X1sigma+ in carbon monoxide.

The dipole-forbidden transition of D1delta <-- X1sigma+ of CO has been observed by a fast electron-energy-loss spectrometer at a large scattering angle of 7 degrees and with an energy resolution of 60 meV. The energy levels and the relative intensity distribution of D1delta, v'=9-25 have been determined, most of the results are reported for the first time.

Dynamical correlation in double excitations of helium studied by high-resolution and angular-resolved fast-electron energy-loss spectroscopy in absolute measurements.

The momentum transfer dependence of fundamental double excitation processes of helium is studied by absolute measurements using an angular resolved fast-electron energy loss spectrometer with high energy resolution. It elucidates the dynamical correlations, in terms of internal correlation quantum numbers, K, T, and A. The Fano profile parameters q, f(a), rho2, f, and S of doubly excited states (2)(1,0)+2 (1)S(e), (2)(1,0)+2 (1)D(e), and (2)(0,1)+2 (1)P(o) are reported as functions of momentum transfer K2. Qualitative analysis is given for the states of (2)(-1,0)+2 (1)S(e) and (2)(1,0)+2 (1)S(e).