Estimation of the electronic excitation cross sections of the 1s → 2s, 2p, 3s, 3p, and 3d transitions in the hydrogen atom on the basis of the Gaussian approximation of the Feynman integral

We continue to verify the method for calculating the scattering cross sections that is based on the Gaussian approximation of path integrals upon calculation of the electronic excitation cross sections. For this purpose, we calculate the electronic excitation cross sections of the 1s → 2s, 2p, 3s, 3p, and 3d transitions in the hydrogen atom using more exact Gaussian approximations for the Coulomb interaction and atomic states. The results show that this method allows one to obtain good agreement with data available in the literature. Comparison with our previous data shows that the use of the refined Gaussian expansions improves the calculation results.     

Lifetime measurements of lithiumD-states

We report lifetime measurements of the 1s ² 3d ² D, 1s ²4d ² D, and 1s ²2p ² P states of lithium. The results τ=14.5±0.7 ns, τ=31.0±1.0 ns, and τ=27.9±1.0 ns respectively were obtained by time resolved detection of the resonance fluorescence following pulsed laser excitation.     

The role of the configuration interaction in excitation of the Cd(II) principal series at electron-atom collisions

The excitation functions of Cd(II) spectral lines, namely, the lines of the 4d ¹⁰5s ² S _1/2?4d ¹⁰ np ² P ₃ ^2/0 (n≤10) principal series and the line corresponding to a transition from the Beitler level 4d ⁹(5s5p ¹ P ⁰)² P ₃ ^2/0 , are analyzed under the conditions of electron-cadmium atom collisions in the electron energy range from excitation thresholds to 400 eV. It is found that the excitation functions of the spectral lines attributed to transitions from the Beitler level are similar to those of the principal series lines corresponding to transitions from the 4d ¹⁰ np ² P ₃ ^2/0 (n=9, 10) levels nearest to the Beitler level. This similarity is explained by the significant admixing of the Beitler level to the initial levels of the principal series lines. It is shown that the admixing substantially affects the excitation functions of this series for the states more distant from the Beitler level (up to n=6).     

Radiative Lifetimes of the Energy Levels of Palladium-like Ions Pr XIV and Nd XV

Radiative lifetimes for the 4d⁹4f, 4d⁹5p, 4d⁹5d, and 4d⁹6s levels in the spectra of palladium-like ions Pr XIV and Nd XV are calculated in the electric-dipole approximation by the intermediate coupling semiempirical method with the use of experimental energy levels available in the literature. The radial integrals of transitions necessary for calculating absolute values of transition probabilities are obtained in the length form with Hartree–Fock functions.     

A test of the absolute Ni(I) gf-value scale by using mean lives of selected levels for the configurations 3d84s4p and 3d94p

Lifetimes for 11 levels of the configurations 3d⁸4s4p and 3d⁹4p in Ni (I) have been measured by the delayed coincidence method, following selective dye-laser excitation in a wavelength range between 299 and 338 nm. The results are compared with earlier laser excitation and Hanle effect lifetime measurements and with lifetimes derived from the gf-values of Huber and Sandeman. Comparisons with the results of Huber and Sandeman show consistently excellent agreement.     

Ionization,charge exchange,and excitation during collisions of sodium ions with argon

The absolute values of cross sections of ionization, charge exchange, and excitation during Na⁺-Ar collisions are measured in the ion energy range 0.5–10.0 keV. Experiments are performed by a modified method of transverse electric field and by the optical spectrometry method. The mechanisms for realization of inelastic channels are explained qualitatively on the basis of a schematic correlation diagram of diabatic quasi-molecular energy levels of a system of colliding particles. The quasi-molecular nature of interaction is revealed for excitation processes. The excitation mechanisms of collision partners are established. A noticeable contribution to the excitation of the 4s state of the argon atom comes from the cascade transition from upper-lying 4p and 3d levels. An oscillatory structure is observed in the excitation functions of atomic lines of ArI (104.8 and 106.7 nm). The shape of the curve describing the dependence of the charge-exchange cross section on the collision energy is explained by the presence of two nonadiabaticity regions. In the low-energy region (up to E = 2 keV), charge exchange is due to electron capture to the ground state as a result of Σ–Σ transitions, while Σ–Π transitions associated with the rotation of internuclear axis play the leading role in charge exchange in the energy range E > 3 keV. The contribution of a number of inelastic channel is estimated for the ionization process. It is found that the main contribution to ionization is associated with the decay of self-ionization states in an isolated atom.     

Analysis of the spectrum of the Zn-like Kr VII ion: Highly excited 4<Emphasis Type="Italic">p</Emphasis>4<Emphasis Type="Italic">d</Emphasis> and 4<Emphasis Type="Italic">p</Emphasis>5<Emphasis Type="Italic">s</Emphasis> configurations

The spectrum of the Zn-like Kr VII ion, excited in a capillary discharge and recorded with a high resolution in the wavelength range of 300–1000 Å, was studied. Previously performed identification of the transitions from the levels of the 4s4f, 4s5s, 4s5p, and 4s5d configurations is confirmed and extended, and the energies of these levels are specified. The (4p ²+4s4d)?4p4d and (4p ²+4s5s)?4p5s transitions are identified for the first time, and the energies of all the levels of the 4p4d and 4p5s configurations are determined. The results of the analysis performed are confirmed by semiempirical calculations in terms of the Hartree-Fock method. These results are also shown to conform to the experimental data obtained for lighter ions of the Zn I isoelectronic sequence.     

Electronic spectra of XeNe molecules in the range 77100-90100 cm-1 near Xe* (6p, 5d, 6p’, 7s, 7p, 6d) obtained by the (3 + 1) REMPI and (2 + 1) REMPI methods

The electronic spectra of XeNe molecules in the range of 77100-90100 cm^-1 are measured by the method of laser resonance multiphoton ionization in a supersonic jet. The photoionization spectra are obtained upon two- and three-photon excitations of molecules and their ionization by the next photon. In the range of 80300-90100 cm^-1 near Xe*(5d, 6p’, 6d, 7s, and 7p), the spectra are obtained for the first time. A whole number of vibrational systems are measured in this range. The majority of vibrational systems near Xe* (5d, 6d, 7p, and 7s) are located in the red range with respect to their dissociation limits. In the blue range with respect to the dissociation limits, continua corresponding to transitions of molecules from the ground state to repulsive potential curves of excited states are detected. For a number of excited states of XeNe molecules, the vibrational analysis is performed and molecular constants are estimated.     

Experimentally determined transition probabilities of the systems 6p2→6p6d, 6p7s, 6p8s of neutral lead

Branching ratio measurements have been performed for all of the observed transitions from eight levels in neutral lead (6p²→6p6d, 6p²→ 6p7s, 6p²→6p8s) excited in a hollow cathode discharge in the 200–730 nm spectral range. From the relative emission intensity data, a set of absolute transition probabilities is derived for 28 lines, including lines for which transition probabilities have not been previously published. The absolute scales are obtained by averaging the measured lifetimes of the ³P⁰_1,2, ¹P_1⁰(6p7s), ³F^0_2,3, ³D^0_1,2(6p6d) levels.     

Determination of transition probabilities for singly ionized vanadium

Transition probabilities of 211 spectral lines of VII, in the wavelength range 2340–4200 Å, have been determined by emission spectroscopy using a wall-stabilized arc as source. The lines studied belong to the transition arrays 3d⁴, 3d³4s-3d³4p (199 lines) and 3d³4p-3d³4d, 3d³5s (12 lines). Vanadium was introduced into the helium-arc discharge as the liquid VOCl₃. An important feature of this work is the determination of transition probabilities for many lines from a wide spectral range with a uniform absolute scale. The absolute A_ki values were obtained by normalizing relative A_ki values to an absolute scale set by ionic lifetime for the level y³H⁰₄. These results are compared with other experimental as well as theoretical results.     

Radiative transition probabilities in ions of the silver isoelectronic sequence

The wave functions of one-electron states above the 4d ¹⁰ core have been calculated within the relativistic perturbation theory with a zero-order model potential. The wavelengths and probabilities of electric dipole transitions in an Ag-like ion have been calculated for the 5s-5p, 5p-5d, 5d-5f, and 4f-5d transitions. The data obtained are compared with the results of calculations by the relativistic Hartree-Fock method and within the relativistic many-body perturbation theory. The theoretical results are compared with experimental data on the lifetimes of energy levels in Ag-like ions.     

Radiative lifetimes of some states of NeII

The radiative lifetimes of eight states of NeII, namely 3d, 3d′, 4s and 4s′, are measured. The delay-coincidence method with pulsed electron excitation is employed. A comparison with other results is also reported.     

Improved infrared and visible emission spectra of the H3 and D3 molecules

Better-resolved Rydberg-Rydberg emission spectra of the neutral H₃ and D₃ molecules in the infrared and visible regions, with less interference from H₂ and D₂ emission, have been obtained by using a Droege-Engelking type of corona discharge source. Using nl_λ notation, the lower electronic states are 3p₁ in the infrared and 2p₀ in the visible, and the upper electronic states are mixed (3s,3p₀,3d₀,3d₁,3d₂) states. In particular, a line near 16 842 cm⁻¹ in H₃, previously obscured by an H₂ line, reveals a (3s,3d) interaction that is confirmed by other lines. The spectra are analysed including this interaction. However, fits to effective Hamiltonians still have relatively large standard deviations, probably partly due to poor convergence of the rotational expansions and partly due to many small perturbations of the levels by background states.     

Ionization of excited states of the hydrogen atom by a laser pulse

The energy spectra of electrons are calculated in the adiabatic approximation when the excited 2s, 2p, and 3d states of the hydrogen atom are ionized by a superstrong ultrashort laser pulse.     

Optische Messung der Elektronenstoß-Anregung von Xenon und molekularem Stickstoff im Schwellenbereich mit hoher Energieauflösung

Relative optical excitation functions of Xe and N₂ have been measured in the threshold region. The inciting electron beam had a FWHM of 50 meV. The threshold behaviour of the excitation functions ofp-levels of Xenon is strongly influenced by resonances. The onset is step-like, in some cases resonance structure is to be seen just above threshold. In some excitation functions resonance structure is found immediatly above the ionization limit. This is believed to be caused by two compound states the parent states of which could be the 6d′ and the 8s′ autoionizing state of Xenon. In nitrogen, the excitation functions of two bands of the second positive group have been measured (3371 and 3755 Å), the upper levels of which are thev=0 and thev=1 levels of theC ³Π _u state. The excitation raises linear from threshold. In the 3371 Å excitation function a resonance maximum at 11.50 eV is observed, where the cross section is increased due to resonance population by about 100%, as measured with a FWHM of 50meV of the electron beam. The broad absolute maximums of the excitation functions are found to lie at 14.0±0.1 eV in the case of the 3371 Å- and at 14.3±0.1 eV in the 3755 Å-band.     

Inner shell excitation and ionization of the monohalobenzenes

Energy loss (excitation) spectra of the gaseous monohalobenzenes, C ₆H ₅X (X = F, Cl, Br and I), were obtained by fast electron impact in the regions of the respective carbon 1 s, chlorine 2 p and 2 s, bromine 3 d and iodine 4 d edges. Gas phase X-ray PES measurements of the binding energies of these levels are also reported. Structure observed below the ionization limits has been interpreted with the aid of term values derived from the two sets of measurements.     

Anomalous behavior of optogalvanic signal in a miniature neon discharge lamp

A strong optogalvanic effect has been observed in a negative glow of a miniature neon discharge lamp using tunable pulse dye laser pumped by a copper vapor laser. A comparative study on temporal evolution of optogalvanic signal in a positive and negative dynamic resistance region of the discharge is described. Dye laser beam was tuned to various neon transitions 1s_i → 2p_j (Paschen notations) within 570-617 nm wavelength range. Anomalous behavior of optogalvanic signal was observed at 588.2 nm for (1s₅ → 2p₂) neon transition at low discharge current (<220 μA). This anomalous behavior is the attributes of damped oscillations of optogalvanic signal that correlate with negative dynamic resistance (dV/di < 0) of the discharge. Penning ionization at low discharge current and small energy mismatch is assumed to be the main cause of the negative dynamic resistance. Penning ionization process has been explained by resonantly ionizing energy transfer via collisions between neon buffer gas atoms in the lowest metastable state (1s₅) and electrode sputtered atoms in ground state using their partial energy level diagram.     

Autoionizing and highly excited states in the spectrum of triply ionized tin Sn IV

Transitions from autoionizing states in the spectrum of Sn IV in the range 200–630 Å, occurring due to the excitation of electrons from the inner 4d ¹⁰ shell, are investigated with high resolution. The transitions from the 4d ⁹5p ², 4d ⁹5s6p, and 4d ⁹5snf (up to n = 9) configurations are identified and their autoionization widths are measured. Transitions from the highly excited 4d ¹⁰ ns (n = 8–10), 4d ¹⁰6p, and 4d ¹⁰7d configurations are also revealed and the ionization potential of Sn IV is refined. The data obtained are compared with the results of calculations by the Hartree-Fock and semiempirical methods.     

Spin interactions in a quantum ring containing a magnetic impurity

The exciton states in a CdTe semiconductor quantum ring containing a single magnetic impurity are considered in an external magnetic field. The electron-hole spin interaction and s,p-d interactions between electron, hole and magnetic impurity are also taken into account in the calculations. It is shown that due to the s,p-d spin interactions the ground state exciton energy splits into 12 doubly degenerated energy levels. The external magnetic field removes this degeneracy. A novel method is proposed here to determine the values of the strengths of s,p-d interactions. The optical spectrum of the system for different polarizations of the incident light and for different initial states of the magnetic impurity spin projection is also studied.     

Radiative constants in the spectra of ions of the krypton isoelectronic sequence

The probabilities of the 4p ⁶,4p ⁵5p→4p ⁵(4d+5s) radiative transitions and the radiative lifetimes of the 4p ⁵4d,4p ⁵5s, and 4p ⁵5p levels are calculated semiempirically for the RbII-MoVII isoelectronic sequence.