Cluster projectile ions used for the SIMS analysis of silicon

Comparative studies of the emission of Si _n ⁺ (n = 1–11) cluster ions and impurity-containing polyatomic ions under bombardment of B-doped single crystal silicon with A _m ^? (m = 1–5) cluster ions with an energy of E ₀ = 6–18 keV are carried out. The peculiarities of sputtering an adsorbed-particle layer with cluster ions are revealed. The possibility of determining the depth distribution of adsorbed particles by analyzing the yield of sputtered heteroatomic molecular ions upon bombardment is demonstrated.     

Statistical mechanism of the formation of the energy spectra of sputtered molecular clusters

The energy spectra of Si _n O _m ^? clusters sputtered from Si targets by Xe⁺ ions with O₂ pumping onto a bombarded surface, as well as by O ₂ ⁺ ions, are studied. It is shown that the form of the Si _n O _2n+1 ^? energy distributions does not depend on the experimental conditions. Significant differences in the energy spectra of O and Si monomers as compared to Si _n O _2n+1 ^? clusters are revealed. The mentioned features of the energy distribution of Si _n O _m ^? clusters are explained within the framework of the statistical recombination mechanism of their formation in combinatorial synthesis processes.     

Indium sputtering upon bombardment with cluster ions

A surface-ionization method is developed for measuring the integral yields of neutral particles sputtered under the effect of ion bombardment. An investigation is performed to compare the integral yield of particles sputtered upon bombarding indium with Bi _m ⁺ cluster ions (m = 1?C7) in the energy range of 2?C10 keV and the secondary ion emission under bombardment with Bi _m ⁺ cluster ions (m = 1?C5) in the energy range of 6?C18 keV. A nonadditive increase in the indium sputtering coefficient is observed with an increasing number of atoms in the bombarding clusters.     

Kinetic-energy release distributions and stability of niobium-carbon clusters sputtered from the surface of niobium carbide by xenon ions

The results of studying the emission and fragmentation of niobium-carbon clusters Nb _m C _n ⁺ synthesized upon sputtering a niobium carbide surface with Xe⁺ ions are presented. The fragmentation channels of Nb _m C _n ⁺ clusters are studied. We present the values of the dissociation energy of some Nb _m C _n ⁺ clusters (m = 1–7, n = 2–8) calculated within the context of the “evaporation ensemble” model and theory of unimolecular reactions based on performed measurements of the kinetic-energy spectra of fragment ions. The obtained results are compared with published data.     

Investigating the dissociation energies of niobium and vanadium oxide clusters synthesized by ion sputtering

The mass distributions and fragmentation routes of Nb _n O _m ⁺ and V _n N _m ⁺ clusters sputtered from an metal surfaces with Xe⁺ ions under O₂ pressure of P = 4?5 × 10^?3 Pa in a bombardment chamber are studied by means of secondary ion mass spectrometry. The spectra of kinetic energy release distribution (KERD) are measured for the most probable routes of the fragmentation of Nb _n O _m ⁺ and V _n N _m ⁺ and clusters, on the basis of which the activation energies of the decomposition (dissociation) of Nb _n O _m ⁺ and V _n N _m ⁺ clusters are determined within the model of evaporative ensemble and the theory of monomolecular reactions. The results show the closeness of the numerical values of dissociation energies derived using both models.     

Secondary ion emission from a GaAs single crystal upon bombardment with Bi<Stack> <Subscript> <Emphasis Type="Italic">m</Emphasis> </Subscript> <Superscript>+</Superscript> </Stack> cluster ions

Secondary-ion mass spectra and energy distributions upon bombarding a gallium arsenide single crystal using Bi_m⁺(m = 1–5) cluster ions with energies of 2–12 keV are investigated. The gallium cluster ion yield grew nonadditively with the number of atoms in the cluster projectiles. A quasi-thermal component found in the energy spectra of secondary Ga⁺ and Ga₂⁺ ions is indicative of the occurrence of the thermal spike mode upon cluster ion bombardment. The quasi-thermal component in the yield of atomic Ga⁺ ions upon bombardment with Bi₂⁺–Bi₅⁺–ions is 35–75%.     

Near resonance charge transfer from a laser excited donor state

A laser induced charge transfer from Na(3p) to hydrogen-ions at different kinetic energies has been studied. An enhancement factor of about 90% in the production rate of Lyman-α radiation has been demonstrated to occur only with H⁺ and Na(3p) atoms reaction; no enhancement was observed with either H ₂ ⁺ or H ₃ ⁺ ions. Absolute cross-section for the production of Lyman-α radiation during the collision of H⁺, H ₂ ⁺ and H ₃ ⁺ ions and Na(3p) and Na(3s) atoms have been measured in the energy range 1–600eV. The charge exchange reactions involving hydrogen-ions and Na(3p) atoms created by two different methods have also been compared.     

Molecular and atomic ions of the elements of the sub-groupsA of the periodic system

The production of positive and negative ions of all elements of the sub-groupsA and some of the sub-groupsB has been investigated as an extension of previous work on Penning sources. Molecular ions of the typeX _n ^± ,n>1 and ions of hydride moleculesX _nH _m ^± ,n,m>1 have been found. The maximum numberm _max of the H atoms bound in the cluster is determined by the position of the element in the periodic system. The yield of the atomic and molecular beams has been measured as a function of the electric source parameters and the different gases maintaining the discharge to establish the production mechanism. The data on ion beam intensities and the state of clustering of molecules are listed in tables.     

Mass spectrometer studies of the ion composition in the pink afterglow

The time dependences of the ion number densities in the pink afterglow of nitrogen, as represented by the ion wall currents, have been measured. The ions were extracted through an orifice from a flow system and analysed by a quadrupol mass spectrometer. It has been found thatN ₂ ⁺ ions are dominating in the early afterglow. With the beginning of the ionization processN ₃ ⁺ and at pressure >6 TorrN ₄ ⁺ become the majority ions. The ratio of the number densities(N ₃ ⁺ )/(N ₂ ⁺ ) reaches a maximum during the increase of the ionization processes before the maximum is reached. This behaviour suggestsN ₃ ⁺ ions to be the primary ions created by the ionization processes. The time dependences of the ion number densities (N ₂ ⁺ ), (N ₃ ⁺ ) and(N ₄ ⁺ ) are found to vary similar, showing that the ions are strongly coupled by conversion processes. The conversion processes are discussed. In the maximum of ionization at a total pressure of 4.4 Torr the ratios of the number densities of the afterglow ions (N ₂ ⁺ )∶(N ₃ ⁺ )∶(N ₄ ⁺) are 1∶1.9∶0.64.     

Study of the formation and unimolecular fragmentation of Si<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>O<Stack><Subscript><Emphasis Type="Italic">m</Emphasis></Subscript><Superscript>+</Superscript></Stack> clusters under ion bombardment

The dependences of the emission and fragmentation of clusters sputtered by Xe⁺ ions from the surface of Si _n O _m ⁺ on the oxygen pressure near the bombarded surface are studied using secondary ion mass spectrometry. It is shown that the process of Si _n O _m ⁺ cluster formation under ion bombardment can be described within the framework of the mechanism of combinatorial synthesis by taking into account the mutual reversibility of the reactions of formation and unimolecular decay.     

Fragmentation processes of vanadium and niobium oxide clusters sputtered by ion bombardment

The mass distribution of emitted V _n O _m ^? and Nb _n O _m ^? clusters and their unimolecular decay by all stoichiometrically possible fragmentation channels, which takes place under the sputtering of niobium and vanadium surfaces and blowing by oxygen, are studied. It is shown that the formation, excitation, and unimolecular fragmentation of V _n O _m ^? and Nb _n O _m ^? clusters can be described by a statistical recombination mechanism. Clusters are formed over the target surfaces as a result of binary collisions of independently sputtered ions, atoms, and molecules.     

Experimental g factor of hydrogenlike silicon-28

Using the first principles calculations, the mixed Au _n Zn _m ⁺ (n + m ?? 6) cluster cations and their monocarbonyls Au _n Zn _m CO⁺ have been investigated at the PW91 level. For the small Au _n Zn _m ⁺ , most ground-state isomers are planar structures. A significant odd-even oscillation of the highest occupied-lowest unoccupied molecular orbital energy gaps with the number of Au atoms is observed. Upon CO adsorption, the top site and C head-on adsorptions are most favorable in energy. Moreover, the optimized geometries indicate that the CO molecule prefers binding to Au atom of the Au _n Zn _m ⁺ clusters, which can be understood by the frontier molecular orbital theory in detail. From the theoretical calculations, the CO charge population, CO binding energy (BE) and the Gibbs free-energy change ??G generally decrease with the increase of the Zn content. It is found that the BE is highly related to the electron transfer between CO and the cluster cations. Furthermore, a linear correlation between ??G and the CO BE is found. The red shift in the CO stretching frequency is sensitive to the cluster size and composition. Our calculation suggests that CO reactive collision on Au₃Zn⁺ and Au₂Zn ₂ ⁺ may lead to the dissociation of the clusters with a Zn atom loss.     

Ionization and dissociative ionization of methane molecules

A technique for mass-spectrometric investigation of the yield of positive ions produced by direct and electron-impact dissociative ionization of methane molecules is described, and respective experimental data are presented. Doubly charged C ₂ ⁺ , CH ₃ ²⁺ , and CH ₄ ²⁺ ions, as well as singly charged D ₂ ⁺ , CD ₃ ⁺ , and CD ₄ ⁺ ions, are detected in the mass spectrum of a methane molecule at electron energy U _e = 90 eV for the first time. From ionization efficiency curves, the ionization energy of the parent molecule and the appearance energy of fragment ions are determined. The ionization energy of the CH₄ molecule is found to be 12.62 ± 0.20 eV. Electron-molecular reactions that may take place when a low-energy electron beam interacts with a methane molecule are analyzed. The ionization process and the formation of methane molecule fragments are studied.     

Multiplicities of charged particles prior to fission

Electric monopole transitions between the 0 ₂ ⁺ , 0 ₁ ⁺ and 2 ₂ ⁺ , 2 ₁ ⁺ levels in⁷⁶Se, populated in the decay of⁷⁶Br, were investigated by means of conversion electrons and gammaray spectroscopy. TheK-electron intensity ratios ofE0 andE2 transitions connecting the 0 ₂ ⁺ level to the 0 ₁ ⁺ and 2 ₁ ⁺ levels and of theE0 andE2 components in the 2 ₂ ⁺ →2 ₁ ⁺ transition were determined. The ratioX(E0/E2) of theE0 toE2 reduced transition probabilities and, from the available lifetimes, theE0 strength parameters ρ(E0) were deduced for the two transitions. The results are compared with the predictions of current models.     

Comparative study of the semiempirical three-parameter potential energy functions for diatomic molecules

A comparative study is made of four three-parameter semiempirical potential energy functions for 32 electronic states of diatomic molecules and their ions:n ₂:X¹gS _g ⁺ ,B ³π_g,A ³ gS_u,C ³ _u,B′ ³ gS_u.a ¹ π_g, a′gS _u ^? ,Ω ¹δ_u N ₂ ⁺ :X ² gS _g ^gS +A ² π,C ² gS _u ⁺ ,B ² gS _u ⁺ CO:X¹gS⁺,a ³ π, a′³ gS_u,e ³ gS^?,d ³gD₁,A ¹π CO⁺:X²gS⁺,A ² π,B ²gS⁺ O₂:X³gS _g ^? ,B ³ gS_u,c ¹ gS _u ^? ,b ¹gS _g ^s ,a ¹ δ_g,c ³ δ_u O ₂ ⁺ :X ²π_g,A ² π_g, a¹ π_g,b ⁴ gS _g ^? A program for numerically integrating the radial Schrödinger equation by the Cooley method is worked out. Certain additional units are introduced to conserve computer time. The resulting vibrational levels are compared with the experimental levels for all the electronic states studied. It is concluded on the basis of this analysis that it is not possible to describe equally well all the electronic states of various molecules on the basis of any single three-parameter potential function. A method for choosing a potential function for describing some particular electronic state of a diatomic molecule is proposed.     

Hölder’s inequality for matrices

We prove that for arbitraryn×n matricesA ₁,A ₂,…,A _m and for positive real numbersp ₁,p ₂,…,p _m withp ₁ ^?1 +p ₂ ^?1 +…+p _m ^/?1 =1, the inequality 1 $$|Tr(A_1 A_2 ...A_m )^2 |< \mathop {II}\limits_{k = 1}^m [Tr(A_k^\dag A_k )^{p_k } ]P_k^{ - 1} $$ holds.     

Xα-SW-calculation of the chemically induced decay constant variation of Tc-99m in the tetrahedral oxy-complex ion and the octahedral halogen-complex ions

The tetrahedral and octahedral complex ions TcO ₄ ^? , TcCl ₆ ^2? , TcBr ₆ ^2? , TcI ₆ ^2? , which exhibit experimentally determined decay constant variations of Tc-99m [1], meet the conditions for the application of the X_α-SW-method. The results of the calculations are given, including the case of TcF ₆ ^2? . The decay constant variations are evaluated using the one-electron functions in a partial-wave expansion. The results are compared with the measured values and a detailed discussion gives a comprehensive picture of the decay constant variation induced by the chemical surroundings considered.     

Pion photoproduction on197Au to ground and isomeric states in197Hg

The lifetime of the 331.3 keV 0 ₂ ⁺ state in¹⁰⁰Zr has been measured at the gas-filled recoil separator for fission products JOSEF. By observing the delayed coincidences between theβ-particles populating the level and theE0 conversion electrons from its decay into the ground state, a half-life of 3.37±0.30 ns has been obtained. From the measured lifetime and the relative intensities of the 0 ₂ ⁺ →0 ₁ ⁺ and 0 ₂ ⁺ →2 ₁ ⁺ transitions, values of 0.493±0.015 for theE0 strength parameterρ, and of 16 single particle units forB(E2,2 ₁ ⁺ → 0 ₂ ⁺ ) have been deduced. The enhanced nature of theE0 transitions suggests mixing of the 0 ₁ ⁺ and 0 ₂ ⁺ states which may be estimated by comparing the experimentalB(E2) values for the 2 ₁ ⁺ →0 ₁ ⁺ and 2 ₁ ⁺ →0 ₂ ⁺ transitions with the predictions of the asymmetric VMI model.     

Electric properties of levels of 156Dy rotational bands

The nonadiabaticity of E0 transitions from 0 ₂ ⁺ states and 2 ₁ ⁺ bands in ¹⁵⁶Dy is examined within a phenomenological model that takes into account the mixing of K ^π = 0 ₁ ⁺ , 0 ₂ ⁺ , 0 ₃ ⁺ , 2 ₁ ⁺ states and 1⁺-bands. It is shown that the nonadiabaticity of E0 transitions is due primarily to the mixing of 0 ₂ ⁺ and 0 ₃ ⁺ bands.     

Investigation of N 2 + (C 2Σ u + → X 2Σ g + fluorescence excited through auger decay of the 1s −1π* resonance

A theoretical investigation of N ₂ ⁺ (C ²Σ _u ⁺ → X ²Σ _g ⁺ molecular fluorescence excited through the Auger decay of the 1s ^?1π* resonance is carried out. The fluorescence cross sections are calculated with due regard for the dependence of the matrix element of the C → X dipole transition on the internuclear distance, the interference between channels of excitation via different vibrational levels v _r of the 1s ^?1π* resonance, the rotational structure of the fluorescence band, and the predissociation of the N ₂ ⁺ C ²Σ _u ⁺ v′ ≥3) states. The calculated cross sections are in good agreement with the experimental results of recent measurements. The results of the calculations have demonstrated that the observed dependence of the cross section of the (C ²Σ _u ⁺ (v′) → X ²Σ _g ⁺ (v″) fluorescence on the excitation energy and the fluorescence wavelength for a group of bands with equal values of the difference Δv = v′ ? v″ is associated with transitions between the vibrational levels of the electronic states involved in the excitation and subsequent cascade decay of the 1s ^?1π* resonance: N₂ (v ₀ = 0) → N*₂(1s ^?1π*(v _r)) ? N ₂ ⁺ : (C ²Σ _u ⁺ (v′) → X ²Σ _g ⁺ (v″).