Fast-electron Energy Loss Spectrometer Research Articles

Generalized oscillator strengths for the valence-shell excitations of xenon studied by the high-resolution fast-electron impact

SynopsisUsing the high-resolution fast-electron energy loss spectrometer, the generalized oscillator strengths (GOSs) of the valence-shell excitations of xenon were determined at a high resolution of 70 meV and a high incident electron energy of 1500 eV, and the momentum transfer dependence behaviors of GOSs of the 6s[3/2]1 and 6s'[1/2]1 excitations of xenon are discussed.

The ionization and dissociation of nitrous oxide studied by fast electron impact

Using the high-resolution fast electron energy loss spectrometer, the generalized oscillator strength densities (GOSDs) of the ion fragments of N2O at different momentum transfers were determined at a high resolution (80meV), and the momentum transfer dependence behavior of the ioniza-tion and dissociation of N2O has been studied.

Inner-shell excitations of krypton3dinvestigated by electron impact with high resolution

The inner-shell excitation spectra of krypton $3d$ electrons were measured at scattering angles of 0\ifmmode^\circ\else\textdegree\fi{} and 4\ifmmode^\circ\else\textdegree\fi{} by a fast-electron energy-loss spectrometer at an incident energy of 2.5 keV with an energy resolution better than 80 meV. Some interesting optically forbidden transitions were observed and the natural widths of the optically allowed and optically forbidden transitions were analyzed. It shows that the natural widths for the resonances having the same core hole are nearly equal, no matter whether they are optically allowed, optically forbidden, or different members of a Rydberg series.

Optical Oscillator Strengths of Hydrogen Bromide inthe 4.5–20 eV Excitation Energy Region

The absolute optical oscillator strength density spectrum of HBr in thevalence shell energy region of 4.5–20 eV has been determined by ahigh-resolution fast electron energy loss spectrometer. The opticaloscillator strengths for the broad a3Π+A1Π dissociation peak andthe discrete transitions of b 3Π1(ν′ = 0) and C1Π(ν′ = 0,1,2)are reported. It has been manifested clearly that the optical oscillatorstrengths of some transitions for the previous photoabsorption methodare subject to severe line-saturation effects.

The generalized oscillator strengths for the valence shell excitations in helium by fast electron impact

The generalized oscillator strengths (GOSs) for the valence shell excitations of 2 1S, 3 1S, 3 1P+3 1D, 4 1S, 4 1P+4 1D, 5 1S+5 1P+5 1D, and 6 1S+6 1P+6 1D in helium were measured by a high-resolution angular-resolved fast-electron energy loss spectrometer at the incident energy of 2500 eV and the value of the momentum transfer square from K 2=0.07 to 3.6 a.u. In the present measurement, the impact energy was higher, and the momentum transfer was higher except for 2 1S. The first Born approximation was reached for these transitions under the present experimental condition. The GOS of 4 1S was measured for the first time.

Optical Oscillator Strengths of Hydrogen Chloride in theEnergy Region of 5.5–20 eV

Absolute optical oscillator strength density (OOSD) spectrum of HCl inthe valence shell energy region of 5.5–20 eV has been determined bythe high resolution fast electron energy loss spectrometer (EELS). Theoptical oscillator strengths for the broad A1Π+13Σ+dissociation peak and the discrete transitions of b3Π(ν′ = 0),C1Π(ν′ = 0,1,2) and M1Π(ν′ = 0) are reported.

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).

Experimental and theoretical investigations of absolute optical oscillator strengths for valence excitations of nitric oxide

The absolute optical oscillator strength density spectra of nitric oxide in the energy region of 5.0-22.0 eV have been measured by a high-resolution fast-electron energy loss spectrometer. With the calculated results obtained by the multiscattering self-consistent-field method and channel characteristics, the strongly overlapped spectra in the energy region of 7.5-9.3 eV have been analysed and the corresponding partially vibrationally resolved optical oscillator strengths have been estimated from the experimental spectra.

Photoabsorption Spectrum and OpticallyForbidden Transitions of Krypton by Electron Impact

A high resolution fast electron energy loss spectrometer withmulti-channel energy analysis was employed. The maxima just above thethreshold 4p-1(2P1/2), which is regarded as a shape resonance,was obtained at 16.3 eV. The optically forbidden excitations of4s electron were measured for the first time, and the energy positionsare 23.75 eV (4s-15s), 25.66 eV (4s-16s/4d) and26.60 eV (4s-17s/5d).

Application of a multichannel detection system to the high-resolution fast electron energy loss spectrometer

A microchannel-plate based resistive-anode position sensitive detection system is applied to a high-resolution fast electron energy loss spectrometer. The biasing voltage divider network for the detector is investigated. The measurement efficiency is increased by about 20 times, and to some extent, the energy resolution is also improved. The static mode and the scanning mode of the spectrometer are discussed in detail. In the scanning mode, a spectrum with higher energy resolution can be obtained through a coarse scanning. As a testing experiment, the optical oscillator strength spectrum for the Rydberg series of helium is measured and the results are compared.