Zhu Lin-Fan

Inner-Shell Excitations of 2p Electrons of Argon Investigated by Fast Electron Impact with High Resolution

Electron energy loss spectra of inner-shell excitations of 2p electrons of argon are measured at an incident electron energy of 2500 eV and scattering angles of 0° and 4°. The dipole-forbidden transitions of 2p−13/24p and 2p−13/25p are observed in the measured spectra and assigned based on the calculations of the Cowan code. The positions and line widths for the excitations of 2p−13/2nl and 2p−11/2nl (n ≤ 5) of argon are determined. The present results show that the line widths of the electric quadrupole transitions of 2p−13/24p[5/2 + 3/2]2 and the electric monopole one of 2p−13/24p[1/2]0 are less than those of the dipole-allowed transitions.

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.

Three-Qubit Entanglement Sudden Death

We study entanglement dynamics of three-qubit system via negativity. Three atoms A, B, and C interact isolatedly with their own Jaynes–Cummings cavities a, b, and c. Aa system is prepared entangled with Bb and Cc, however, their mutual isolations forbid Aa interacting with system Bb and Cc. It is the same for system Bb and Cc. We show entanglement evolution of different three-qubit systems ABC, abc, Abc, and aBC and find entanglement sudden death effect.

Valence-Shell Excitations of Nitrous Oxide Studied by Fast Electron Impact

The valence-shell excitations of nitrous oxide are studied by fast electron energy loss spectroscopy. From the spectra measured at 2.5 keV and scattering angles of 3.5°–8.5°, it is found that the asymmetric peak of the transition B1Δ can be well fitted by Haarhoff-Van der Linde function, while the symmetric peaks of the transitions of C1Π and D1Σ+ can be well fitted by the Voigt function. The parameters of the peak profiles of B1Δ, C1Π and D1Σ+, i.e., their energy level positions and linewidths, are determined. With the aid of these parameters, the overlapping spectra measured at the low-energy electron impact can be deconvolved, which provides the possibility to determine the quantitative differential cross sections. The present results also show that the peak profiles of the transitions of B1Δ, C1Π and D1Σ+, are independent of the momentum transfer.

Optically Forbidden Excitations of 2s Electron of Neon Studied by Fast Electron Impact

The electron energy loss spectrum in the energy region of 42-48.5 eV of neon is measured with an angle-resolved fast-electron energy-loss spectrometer at an incident electron energy of 2500 eV. Besides the dipole-allowed au-toionization transitions of 2s-1 np (n = 3,4) and 2p-2 3s3p, the dipole-forhidden ones of 2s-1 ns (n = 3 — 6) and 2s-1 3d are observed. The line profile parameters, i.e. Er, F and q for these transitions, are determined, and the momentum transfer dependence behaviour is discussed.

Optical Oscillator Strengths for 32S → 42P and 32S → 52P Excitations of Na

The electron-energy-loss-spectrum of sodium has been measured in discrete region at a 1.5 keV impact energy and a mean scattering angle of 0°. The relative optical oscillator strength density spectrum of the valence shell of sodium was established by using the dipole (e, e) method and then normalized to the theoretical optical oscillator strength of the 32S → 32P excitation. The optical oscillator strengths of the 32S → 42P and 32S → 52P excitations obtained in the present work are 0.014 ± 0.002 and 0.0026 ± 0.0004, respectively. Theoretical values of optical oscillator strengths for 32S → n2P (n = 3 - 5) excitations of sodium were obtained by using the relativistic configuration interaction method, which are 0.97, 0.012, and 0.0025, respectively.

Decay pathways of superexcited states of nitrous oxide

The ionization and ionic dissociation of the superexcited state of N2O are studied by using electron energy loss spectroscopy and positive ion time-of-flight mass spectroscopy at different momentum transfers; that is, 0 and 0.23 a.u. (atomic unit). The transitions at 13.8 eV and 14.0 eV are reassigned as 3pπ(000) and 3pσ(000) converging to A2Σ+, respectively. The competition between the main decay pathways of superexcited states at different momentum transfers is revealed. It is found that 3dσ converging to C2Σ+ mainly decays into N2O+ while 4dσ can decay into both N2O+ and NO+.

Momentum transfer dependence behaviors of ionization and dissociation of oxygen

The decay pathways of the structured ionization region of oxygen at different momentum transfers, i.e., 0, 0.23 a.u. (atomic unit), and 0.91 a.u., are studied by measuring the ion and the scattered electron coincidently. It is found that the dipole-forbidden superexcited states of (2σu)−1(c4Σ−u)npσu 3Σ−g ← X3Σ−g decay into different channels according to the principal quantum number n. The broad ridge above 35 eV, which may be due to inner-valence excited states of (2σg)−1nλ or multiply excited states, is observed both at small and large momentum transfers, and its decay channel of O++O is dominant.

Inner Shell Excitations of Lithium Studied by Fast Electron Impact

Electron energy loss spectra for the inner shell excitations of atomic lithium are measured at an incident electron energy of 2500eV and scattering angles of 0°, 2°, 4° and 6°. Two optically forbidden transitions of (ls2s2)2 S and (1s2s3S)3s2 S are observed. The generalized oscillator strength ratios for Is{2s2p3 P)2P0 to 1s(2s2p1P)2P0 were determined, and they are independent of the momentum transfer.

Generalized oscillator strengths for some higher valence-shell excitations of krypton atom

The valence-shell excitations of krypton atom have been investigated by fast electron impact with an angle-resolved electron-energy-loss spectrometer. The generalized oscillator strengths for some higher mixed valence-shell excitations in 4d, 4f, 5p, 5d, 6s, 6p, 7s ← 4p of krypton atom have been determined. Their profiles are discussed, and the generalized oscillator strengths for the electric monopole and quadrupole excitations in 5p ← 4p are compared with the calculations of Amusia et al. (Phys. Rev. A 67 022703 (2003)). The differences between the experimental results and theoretical calculations show that more studies are needed.