Inner-shell Excitation Processes Research Articles

Study of inner-shell excitation processes from N(1s) orbitals in N2O molecules by electron impact

A combination of the iterative Schwinger variational method with the distorted-wave approximation is applied to study excitations of a core-level electron in a triatomic molecule by electron impact. More specifically, we report calculated differential and integral cross sections for the X1Σ+ → 1,3Π(2σ → 3π) and X1Σ+ → 1,3Π(3σ → 3π) transitions in N2O in the 415–900 eV incident energy range. The RI(1:3) ratios, obtained via dividing the distorted-wave integral cross sections for transitions leading to the singlet core-excited states by those leading to triplet states, are also reported. The generalized oscillator-strength profiles for the singlet transitions have also been calculated at the incident energy of 3400 eV. The comparison of these quantities with the available theoretical and experimental data reported in the literature is encouraging.

Core excited states in BF 2Cl and BFCl 2

The mixed boron halides BF 2Cl and BFCl 2 exist in a statistical equilibrium with BF 3 and BCl 3 and cannot be isolated pure. This work has shown that inner-shell excitation processes in these unsymmetrical halides can be studied using specific mass selected fragment ions. The photoion yield spectra have been recorded by means of monochromatized synchroton radiation in the energy range 190–210 eV. Electronic transitions have been assigned on the basis of estimated B(1s) ionization energies (BF 2Cl:201.8 eV; BFCl 2:200.8 eV) and a correlation with core excited states in BF 3 and BCl 3. In agreement with the MO theory, BF 2Cl and BFCl 2 show four resonances. Two of them, in the case of BF 2Cl, are shape resonances with term values −2.7 and −4.0 eV, respectively.

Observation of the heliumlike Ti XXI emission lines from Doublet-III tokamak plasmas.

We have measured the emission lines of the heliumlike Ti xxi impurity radiation from Ohmically heated Doublet-III tokamak plasma discharges. The measured wavelengths are in good agreement with recent theoretical and experimental results. The theoretical and experimental line-intensity ratios are also in good agreement for the pure-dielectronic-recombination satellite lines. Furthermore, collisional inner-shell excitation processes are observed to contribute significantly to the q lines in tokamak plasmas.

The influence of electron-electron interaction on inner-shell excitation processes in heavy-ion collisions

The authors present calculations of electron excitation rates in heavy-ion collisions, in which the electron-electron interaction is treated within a relativistic self-consistent field approach. In comparison with earlier calculations neglecting electron shielding, the authors obtain increased probabilities for K-hole and delta -electron production, whereas the total positron yield decreases. Computed probabilities are compared with available experimental data.

Two-level model for inner-shell excitation: Effect of translation factors

An analytic model is derived for long-range coupling in inner-shell excitation processes of ion-atom collisions using a two-state wave function with Bates and McCarroll translation factors. The result we derive for the sharing ratio reduces to the Demkov result in the low-velocity limit. At higher velocities, we predict a sharing ratio which drops below the Demkov curve. As the velocity increases, a maximum is reached and the sharing ratio then decreases with further increase in velocity. Numerical calculations using translation factors in a molecular orbital basis have shown such a falloff. The effect has been previously attributed to phasing between interaction regions due to a multistate configuration. We show that the effect is due to the inclusion of translation factors. The modification we derive to the analytic model of Demkov resolves discrepancies with the experimental data which were previously attributed to fluorescence yield problems. In addition, we find that without making adiabatic assumptions in treating the solutions of the equations of motion, we can recover the exact Born result in the high-velocity limit.

Failure of single electron descriptions of molecular orbital collision processes

Inner-shell excitation occurring in low and moderate (keV range) energy collisions between light atomic and ionic systems is frequently describable in terms of molecular promotion mechanisms, which have been extensively explored both theoretically and experimentally. The bulk of such studies have concentrated on processes understandable through the use of single- and independent-electron models. Nonetheless, it is possible to find cases of inner-shell excitation in relatively simple collision systems which involve nearly simultaneous multiple-electron transitions and transitions induced by inherently two-electron interactions. Evidence for these many- and non-independent-electron phenomena in inner-shell excitation processes and the importance of considering such effects in the interpetation of collisionally induced excitation spectra is discussed.

K-vacancy production in heavy-ion collisions. I. Experimental results forZ≥35projectiles

We have determined projectile and target $K$ x-ray cross sections from a variety of targets spanning the periodic table and bombarded by 12-60-MeV Br, 200-330-MeV Kr, 15-80-MeV I, 326-470-MeV Xe, and 90-110-MeV Pb. Most targets were thick solids, but, to assure proper extraction of cross sections, some thin solid and gas targets have also been used. The present paper mainly gives experimental details and describes the method of cross-section determination. In subsequent papers various features of the target dependence of the cross section will be examined in terms of atomic and molecular models of inner-shell excitation processes.

Spectres d'absorption dans l'ultraviolet lointain de Be, B, C, N, Mg, Al ET Si

An original absorption-spectroscopy technique developed in 1968 allowed observations of structures in the photoionization continuum of a variety of light elements such as Be, B, C, N, Mg, Al and Si. The method utilizes two vacuum sparks, one of them providing the background continuum, the other one generating the absorbing medium. Results obtained with this technique, which has been improved and extended, are presented. Seventy five new discrete features have been observed and identified corresponding to autoionizing levels with two-electron excitation or single subshell or inner-shell excitation processes.