Radiative decay and autoionization in the4 D-states of the 3d 94s5s configuration in CuI

The CuI 3d ⁹4s5s ⁴ D-states, which lie above the ionization limit, were populated by stepwise collisional and laser excitation. With respect to their total angular momentum, the⁴ D-states have completely different decay modes. Whereas the lifetimesτ(⁴ D _7/2)=8.2(4)·10^?9s andτ(⁴ D _1/2)=7.9(6)·10^?9 s are determinrd by radiative transitions and were measured by time-resolved spectroscopy, the lifetimesτ(⁴ D _5/2)=1.59(6)·10^?12s andτ(⁴ D _3/2)=1.28(5)·10^?12s are due to autoionization and were deduced from the widths of the excitation signals observed by ion detection.     

A monte-carlo/molecular dynamics study of the diffusional recombination kinetics of C(a) + O(a) → CO(g) on Pt(111)

The diffusion constants for C and O adsorbates on Pt(111) surfaces have been calculated with Monte-Carlo/Molecular Dynamics techniques. The diffusion constants are determined to be D_C(T)=(3.4 × 10^?3e^{$\text{?13156}\text{T}$})cm²s^?1 for carbon and D_O(T) = (1.5×10^?3 e^{$\text{?9089}\text{T}$}) cm² s^?1 for oxygen. Using a recently developed diffusion model for surface recombination kinetics an approximate upper bound to the recombination rate constant of C and O on Pt(111) to produce CO_(g) is found to be (9.4×10^?3 e^{$\text{?9089}\text{T}$}) cm² s^?1.     

Stark-Effekt-Untersuchungen der Hyperfeinstruktur der 5s25d2D3/2- und 5s25d2D3/2-Terme im In I-Spektrum

The level-crossing technique with combined electric and magnetic fields was used to investigate the hyperfine structure of the 5s ²5d ² D _3/2- and 5s ²6d ² D _3/2-stedes of the In I-spectrum. From the shifts of the level-crossing signals due to the Stark effect of the electric field the Stark constantsβ of both states were deduced: 5s ²5d ² D _3/2: ¦β¦=0.33(3) Mc/(kV/cm)² 5s ²6d ² D _3/2: ¦β¦=6(1) Mc/(kV/cm)². By theoretical calculations with wave functions of the Coulomb approximation one can show, that the Stark effect in both states is mainly due to admixtures of the 5s ²6p- resp.5s ²7p-configuration.     

Lithium diffusion in Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>-based electrodes: a joint analysis of electrochemical impedance,cyclic voltammetry,pulse chronoamperometry,and chronopotentiometry data

In order to establish the mechanism and to determine the parameters of lithium transport in electrodes based on lithium-vanadium phosphate (Li₃V₂(PO₄)₃), the kinetic model was designed and experimentally tested for joint analysis of electrochemical impedance (EIS), cyclic voltammetry (CV), pulse chronoamperometry (PITT), and chronopotentiometry (GITT) data. It comprises the stages of sequential lithium-ion transfer in the surface layer and the bulk of electrode material’s particles, including accumulation of lithium in the bulk. Transfer processes at both sites are of diffusion nature and differ significantly, both by temporal (characteristic time, τ) and kinetic (diffusion coefficient, D) constants. PITT data analysis provided the following D values for the predominantly lithiated and delithiated forms of the intercalation material: 10^?9 and 3 × 10^?10 cm² s^?1, respectively, for transfer in the bulk and 10^?12 cm² s^?1 for transfer in the thin surface layer of material’s particles. D values extracted from GITT data are in consistency with those obtained from PITT: 3.5–5.8 × 10^?10 and 0.9–5 × 10^?10 cm² s^?1 (for the current and currentless mode, respectively). The D values obtained from EIS data were 5.5 × 10^?10 cm² s^?1 for lithiated (at a potential of 3.5 V) and 2.3 × 10^?9 cm² s^?1 for delithiated (at a potential 4.1 V) forms. CV evaluation gave close results: 3 × 10^?11 cm² s^?1 for anodic and 3.4 × 10^?11 cm² s^?1 for cathodic processes, respectively. The use of complex experimental measurement procedure for combined application of the EIS, PITT, and GITT methods allowed to obtain thermodynamic E,c dependence of Li₃V₂(PO₄)₃ electrode, which is not affected by polarization and heterogeneity of lithium concentration in the intercalate.     

Desorption kinetics and directional dependence of the surface diffusion of potassium on stepped W(100) surfaces

Using a surface ionisation ion microscope the desorption parameters and the diffusion constant of potassium were measured on stepped W(100) surfaces. The activation energy of ionic desorption as well as the corresponding prefactor do not depend on the step density; the mean adsorption lifetime τ can be expressed as τ=1.6×10^?14s exp(2.44 eV/kT).Whereas the surface diffusion of potassium on “flat” W(100) and on W(S)-[9(100)×(110)] was found to be isotropic, on W(S)- [5(100)×(110)] and W(S)-[3(100)×(110)] it occurs preferentially parallel to the step direction. The diffusion constant D_∥ for this direction has roughly the same value for all investigated surfaces: D_∥=7.8×10^?2 cm²s^?1 exp(?0.42 eV/kT). For the direction perpendicular to the steps D⊥ depends on the step density, whereby the activation energy as well as the prefactor increase with increasing step density.     

Relaxation of 5s2 2D3/2 states of Cd ions in He atom collisions in a He-Cd medium excited by fission fragments

Efforts to obtain lasing at the 325 nm CdII transition in a high pressure He-Cd medium pumped by the nuclear reactions products were unsuccessful, in contrast with the same 441.6 nm transition. Experiments carried out at the fast burst nuclear reactor in order to obtain information about the relative intensities of the 441.6 and 325 nm luminescence lines as a function of pressure have allowed to evaluate the constant of the reaction Cd⁺ (5s^{2 2}D_3/2) + He Cd⁺ (5s^{2 2}D_5/2) + He, which has been found to be about 1.5×10^–13 cm³/s. Thus the intensities of the 441.6 and 325 nm luminescence lines measured in a nuclear pumped He-Cd medium are almost equal and the hypothesis about the strong deexcitation of the Cd⁺(5s^{2 2}D_3/2) state by He has not been confirmed.     

Theoretical modelling of XBn T2SLs InAs/InAsSb/B-AlAsSb mid-wave detector operating below thermoelectrical cooling

The paper reports on the barrier mid-wave infrared InAs/InAsSb (x_Sb = 0.4) type-II superlattice detector operating below thermoelectrical cooling. AlAsSb with Sb composition, x_Sb = 0.97; barrier doping, N_D < 2×10¹⁶ cm^?3 leading to valence band offset below 100 meV in relation to the active layer doping, N_D = 5×10¹⁵ cm^?3 was proved to be proper material not introducing extra barrier in valence band in the analyzed temperature range in XBn architectures. The detectivity of the simulated structure was assessed at the level of ～ 10¹¹ Jones at T ～ 100 K assuming absorber thickness, d = 3 μm. The detector’s architecture for high frequency response operation, τ_s = 420 ps (T ～ 77 K) was presented with a reduced active layer of d = 1 μm.     

Kinetics of luminescence induced by sputtering metallic cadmium by a pulsed fast electron beam in helium

Results of an experimental study of the kinetics of luminescence observed when a metallic cadmium foil is bombarded in a helium medium by a 3-ns pulsed beam of 150-keV fast electrons are reported. The foil was irradiated at gas pressures from 76 to 2280 Torr. At a foil temperature of T = 240° C, the de-excitation time of the Beitler levels of the Cd II ion was measured as a function of the buffer gas pressure and the constant of collision quenching of the 5s22D_5/2 level of Cd II by He atoms was determined as k ≈ 3 × 10^-29 cm⁶/s. The experimental data were compared with calculations performed for the gas—vapor mixture in order to find the fraction of excited Cd II ions in the 5s²2D_5/2 state produced directly as a result of sputtering of metallic cadmium by high-energy electrons and by components of the helium plasma. At a helium buffer gas pressure of P ≤ 2.5 atm and a temperature of the cadmium target of T = 240° C, the value of this quantity was found to be α = 0.28 + 0.23P (where P is the helium pressure in atmospheres).     

The defect structure of silver-doped CdS

High-temperature Hall effect measurements are carried out on CdS doped with 2·5 × 10¹⁷?2·3 × 10²⁰ Ag cm^?3 under various cadmium and sulfur pressures. At high p_cd and low silver concentrations, Ag acts as a donor. At higher concentrations self compensation occurs. An anomalous variation of the Hall coefficient with p_s2 indicates that the electron concentration increases with increasing p_s2. This is attributed to the formation of anti structure defects S_cd. A complete defect model is proposed, and published solubility and diffusion data for Ag in CdS in equilibrium with (Ag, Cd) alloys are reinterpreted on the basis of this model.     

Tunable laser study of the ν10 + ν11 band of cyclopropane

Diode laser measurements of the ν₁₀ + ν₁₁ (l_tot = ±2) perpendicular band of cyclopropane have led to the assignments of roughly 600 lines in the 1880–1920-cm^?1 region. Most of the spectra were recorded and stored in digital form using a rapid-scan mode of operating the laser. These spectra were calibrated, with the aid of a computer, by reference to the R lines of the ν₁ + ν₂ band of N₂O. The ground state constants we obtained are (in cm^?1) B = 0.670240 ± 2.4 × 10^?5, D_J = (1.090 ± 0.054) × 10^?6, D_JK = (?1.29 ± 0.19) × 10^?6, D_K = (0.2 ± 1.1) × 10^?6. The excited state levels are perturbed at large J values, presumably by Coriolis couplings between the active E′(l_tot = ±2) and the inactive A′(l_tot = 0) states. Effective values for the excited state constants were obtained by considering only the J < 15 levels. The A₁-A₂ splittings in the K′ = 1 excited states were observed to vary as q_effJ(J + 1), with q_eff = (2.17 ± 0.17) × 10^?4 cm^?1.     

Dy-doped Lu2SiO5 single crystal: spectroscopic characteristics and luminescence dynamics

Spectroscopic and kinetics properties of Lu₂SiO₅:Dy³⁺ (LSO:Dy) single crystal with 1 and 5 at.% of activator were investigated. The polarised absorption and unpolarised emission spectra were measured at 10–300 K. Parameters characterising radiative relaxations of LSO:Dy were estimated by the Judd–Ofelt model. The crystal-field energy structure was derived from low-temperature optical spectra exhibiting the presence of two non-equivalent Dy³⁺ sites. It was found that dysprosium ions in site 1 and in site 2 do not form isolated subsystems; these subsystems are coupled by an effective spectral energy migration process. The LSO:Dy crystal exhibits a strong luminescence in the visible. Strong ion–ion interactions were observed for LSO:Dy (5 at.%); luminescence decays are non-exponential and the macro-parameter of donor–acceptor interaction C _da amounts to 5.3 (10^?52 m⁶?s^?1) and 7.8 (10^?52 m⁶?s^?1) at 10 and 300 K, respectively. Laser potential related to the ⁴F_9/2→⁶H_13/2 yellow luminescence in Dy:LSO was assessed based on evaluation of the emission cross section values. It was concluded that the crystal is a promising material for visible laser operation.     

Chemisorption of H2 on W(100): Absolute sticking probability,coverage, and electron stimulated desorption

Measurements of both the absolute sticking probability near normal incidence and the coverage of H₂ adsorbed on W(100) at ~ 300K have been made using a precision gas dosing system; a known fraction of the molecules entering the vacuum chamber struck the sample crystal before reaching a mass spectrometer detector. The initial sticking probability S₀ for H₂/W(100) is 0.51 ± 0.03; the hydrogen coverage extrapolated to S = 0 is 2.0 × 10¹⁵ atoms cm^?2. The initial sticking probability S₀ for D₂/W(100) is 0.57 ± 0.03; the isotope effect for sticking probability is smaller than previously reported. Electron stimulated desorption (ESD) studies reveal that the low coverage β₂ hydrogen state on W(100) yields H⁺ ions upon bombardment by 100 eV electrons; the ion desorption cross section is ~ 1.8 × 10^?23 cm². The H⁺ ion cross section at saturation hydrogen coverage when the β₁ state is fully populated is ? 10^?25 cm². An isotope effect in electron stimulated desorption of H⁺ and D⁺ has been found. The H⁺ ion yield is ? 100 × greater than the D⁺ ion yield, in agreement with theory.     

The bending vibration bands ν4 and ν5 of HCCI

The bending vibration bands ν₄ and ν₅ of HCCI were studied. From the observed rotational structure the rotational constant B₀ and the centrifugal distortion constant D₀ were obtained. The results were B₀ = 0.105968(7) cm^?1 and D₀ = 1.96(7) × 10^?8 cm^?1 from ν₄ and B₀ = 0.105948(8) cm^?1 and D₀ = 1.96(11) × 10^?8 cm^?1 from ν₅. The structure of the hot bands 2ν₅(Δ) ← ν₅(Π) and 3ν₅(φ) ← 2ν₅(Δ) was also resolved and hence the values α₅ = ?3.033(8) × 10^?4 cm^?1 and q₅ = 9.3(3) × 10^?5 cm^?1 could be derived. The other most intense hot bands following ν₅ could be explained in terms of the Fermi diads $\text{ν}{}_3\text{2ν}{}_5{}^0$ and $\text{ν}{}_3\text{+}\text{ν}{}_5{}^{\mathrm{\pm 1}}\text{3ν}{}_5{}^{\mathrm{\pm 1}}$. Of the numerous hot bands accompanying ν₄, only those between different excited states of ν₄ could be assigned. Then estimates for α₄ and q₄ were also obtained. In addition, several vibrational constants were derived.     

Chemical diffusivity of lithium in LiyTi1+xS2

Chemical diffusivity of lithium was measured in polycrystalline Li_yTi_1+xS₂ using current—pulse relaxation technique on Li/1M LiC1O₄ in THF/Ti_1+xS₂ cell. Excess titanium of the nonstoichiometric titanium disulfide did not so much reduce the lithium diffusivity in the interlayer region as in the case of sodium. The diffusivity varied with the amount of intercalated lithium. It had a maximum value of 5 × 10^?8cm²/s for all compounds of Ti_1+xS₂ (0?x?0.13) when the calculations were based on the geometrical surface area. It was calculated as about 3 × 10^?10cm²/s using the effective surface area.     

Effect of temperature and activator concentration on relaxation of excited states of Eu in K5Li2La1−xEuxF10 crystals

Single crystals of K₅Li₂La_1−xEu_xF₁₀ (where x=0.01,0.03,0.1,0.25,0.50,1) have been obtained from anhydrous fluorides by solid state reaction and then by the Bridgman crystal growth process. Optical properties of crystals were investigated at various temperatures between 5 and 300 K. Energy level scheme for Eu³⁺ has been constructed based on absorption and emission spectra recorded at 5 K. Emission from ⁵D₃, ⁵D₂, ⁵D₁ and ⁵D₀ levels has been studied in detail. It has been found that emission originating from the ⁵D₀ and ⁵D₁ levels is efficient and long lived for all Eu³⁺ concentrations. Estimated selfquenching rate of the ⁵D₁ luminescence is as small as about 10³ s⁻¹ in K₅Li₂EuF₁₀. Temperature dependence of this selfquenching is found to be consistent with a cross-relaxation process in which a donor ion makes the ⁵D₁-⁵D₀ transition and an acceptor ion makes the ⁷F₁-⁷F₃ transition. The ⁵D₂ luminescence is considerably strongly influenced by activator-activator interaction but it is still easily detectable. The ⁵D₃ luminescence is completely quenched in K₅Li₂EuF₁₀.     

Measurement of Ar(I) and Ar(II) transition probabilities in LTE ARC plasmas

The transition probabilities of two Ar(I) lines and one Ar(II) line have been measured in emission on wall-stabilized argon arc plasmas (0·5×10⁵?p, Nm^-2?3×10⁵; 10,000?T, K?20,000; 10²²?N_e, m^-3?5×10²³) using the “method of best fit (MBF)”. The results (without line-wing correction) are for Ar(I) at 714·7 nm, A_nm=5·66×10⁵ s^-1±5%; for Ar(I) at 430·0 nm, A_nm=3·40×10⁵ s^-1±5%; for Ar(II) at 480·6 nm, A_nm=8·82×10⁷ s^-1±7%. These values were not influenced by deviations from LTE, which have been observed at electron number densities n_e?10²³ m^-3. The small uncertainties were achieved after careful corrections of different sources of error.     

Level-Crossing-Experimente zur Untersuchung der Hyperfeinstruktur des 5d 2 D 5/2-Terms im Indium I-Spektrum

The resonance fluorescence of the transition 5d ² D _5/2?5p ² P _3/2 (λ=3256Å) in the In I-spectrum was observed as a function of an external magnetic field. From the level crossing signals the following values of the hyperfine constantsA andB of the 5d ² D _5/2-state were deduced: ¦A¦=148(8) Mc/sec·g _J/1.2 and ¦B/A¦≦0.3. The widths of the signals yielded the mean lifetimet=7.1 (6)·10^?9 sec · 1.2/g _J . From the shifts of the signals caused by a constant electric field parallel to the magnetic field the value of the Stark parameter ¦β¦=0.19(4) Mc/sec/(kV/cm)² ·g _J /1.2 and the sign of the ratioA/β<0 were determined. Calculations with Coulomb wave functions show that the Stark shifts of the electric field are mainly due to admixtures of the 6p ² P _3/2-state.     

Influence of Ar, Ne, Xe, and CCl4 impurities on luminescence kinetics of Cd II ions (5s22D5/2-5p2P3/2 transition, λ = 441.6 nm) in He-Cd mixture

The luminescence kinetics of the Cd II ion at a wavelength of 441.6 nm has been studied experi-mentally in a high-pressure He-Cd mixture in the presence of Ar, Ne, Xe, and CCl₄ impurities. Cadmium ions were excited through the bombardment of a cadmium foil heated up to 240°C by a pulsed electron beam with an electron energy of 150 keV, a pulse duration of 3 ns, and a current of 500 A. The constants of collisional quenching of the Cd II 5s ^{2 2} D _5/2 level by Ar, Ne, and Xe atoms and CCl₄ molecules and the integral luminescence quenching constants of this level in the helium medium by these impurity gases have been determined. The constants of collisional quenching appeared to be 8.1 × 10⁻¹² (Ar), 1.2 × 10⁻¹² (Xe), 1.5 × 10⁻¹³ (Ne), and 1.8 × 10⁻¹⁰ cm³/s (CCl₄, for λ = 325 nm), while the integral constants were found to be, respectively, 4.1 × 10⁻¹¹, 3.4 × 10⁻¹¹, 9.5 × 10⁻¹², 1.4 × 10⁻⁹ cm³/s for Ar, Ne, Xe, and CCl₄ at a buffer gas pressure of 1 atm. Original Russian Text ? A.I. Miskevich, Liu Tao, 2009, published in Optika i Spektroskopiya, 2009, Vol. 107, No. 1, pp. 45–49.     

Measurement of the lifetime of the3 P 2 and4 P 5/2 states in Ar16+ and Ar15+

Promptly decaying levels in Li- and Be-like Ar could be identified in the delayed x-ray and electron spectrum in addition to the four known metastable (1s2s)¹ S ₀, (1s2s)³ S ₁, (1s2p)³ P ₂, and (1s2s2p)⁴ P _5/2 states in He- and Li-like systems. The states having lifetimes of about 10^?14s still contribute to the spectrum observed 10^?9s after the ions have passed a foil. This observation is explained by cascading processes from states of high principal quantum numbern≧14. The measured lifetime of the⁴ P _5/2 state subtracting the contribution of cascades is (0.594±0.016) ns and slightly larger than the theoretically predicted value of 0.563 ns. The³ P ₂ state is depopulated at short distances behind the foil by cascading processes. Its measured lifetime of (1.44±0.08) ns compares to a theoretical value of 1.48 ns.     

Natural radiative lifetimes in the2S1/2 and2D5/2,3/2 sequences of aluminum

Natural radiative lifetimes have been measured for the 3s ² ns ² S _1/2 (n≦10) and 3s ² nd ² D _5/2,3/2 (n≦11) sequences of aluminum using pulsed laser excitation of an atomic beam. The investigated states were populated from the ground configuration using UV pulses of wavelength down to 210 nm produced by a Nd: YAG- or an excimer-pumped dye-laser system. TheS-state lifetimes increase regularily with increasing principal quantum number but this is not the case for theD sequence.