Mass spectrometry of neutral molecules sputtered from polycrystalline metals by Ar+-ions of 100–1000 eV

The flux of neutral particles sputtered from clean polycrystalline targets of 11 metals has been studied by mass spectrometry after being postionized in a low pressure hf plasma. Besides atoms Me₁, postionized metal molecules Me₂ and Me₃ have been detected. The energyE ₀ of the bombarding Ar⁺ ions has been varied between 100 and 1000 eV. Considering the different plasma influences, an attempt is made to obtain the initial composition of the beam of sputtered neutrals from the ratiosR ₂₁ andR ₃₁ of postionized molecules Me₂ and Me₃ to postionized atoms, Me₁, respectively. The influence of the bombarding energyE ₀ onR ₂₁ has been measured for all target elements, onR ₃₁ for Pd and Ag. The yields of Me₂ atE ₀=1 keV approximately appear to be proportional to the square of the total sputtering yieldS for the different target materials. This behaviour and the energy dependence ofR ₂₁ andR ₃₁ are discussed in view of a possible molecule formation process in sputtering.     

Experiments on the sputtering of neutral Cu2 dimers from Cu by Ar+ ions (60–300 eV)

A planar polycrystalline copper target was bombarded normally by Ar⁺ ions with energies ranging from 60 to 300 eV. in the source of a mass spectrometer. The neutral particles sputtered normally from the target were post-ionized and analyzed in the mass spectrometer. A thermionically sustained, magnetically confined low pressure arc plasma was used to supply the bombarding ions, and for post-ionization of the neutral sputtered species. It was found that the relative yields of the sputtered neutral post-ionized Cu₂ dimers are linearly proportional to S², where S is the total sputtering yield for Ar⁺ -Cu. The results support the recombination model for the formation of neutral dimers in sputtering.     

Sputtering—a review of some recent experimental and theoretical aspects

After a brief outline of the present sputtering theory for a random solid, recent results of the sputtering yieldS for polycrystalline targets are discussed, in particular in view of the influence of the projectile mass and the bombarding angle. The angle dependence ofS at low bombarding energies, and results on the angular distribution of sputtered particles for oblique ion incidence point out necessary modifications of present sputtering theories with respect to the anisotropy of the collision cascades in the solid and the influence of the target surface. The energy distribution of the neutral particles ejected along the target normals is related to the theoretically predictedE ^?2-distribution of low energy recoils in the Recent mass spectrometric studies of postionized sputtered neutrals are discussed in view of the formation of sputtered molecules and the application of sputtered neutral mass spectroscopy for surface analysis. Finally, the paper deals with ion-induced surface effects on non-elementary sputtering targets, and the protracted removal of foreign atoms from a matrix.     

Low energy sputtering of neutral Cu2 molecules

The ratios of relative yields of neutral sputtered Cu₂ molecules to neutral sputtered Cu atoms were found to be linearly proportional to the sputtering yield of Cu, from a Cu target under bombardment by Ar⁺ ions (energy 50–90 eV), as determined by secondary neutral mass spectrometry.     

The forced magnetostriction of nickel at 4.2 K

The forced volume magnetostriction of polycrystalline nickel at 4.2 K has been determined with a relative accuracy of 2 × 10^?2. Combining our result with previous data on the forced magnetostriction, we derive for the forced magnetostriction constants: h'₀ = (40 ± 1) × 10^?8T^?1, h'₁ = (-95 ± 2) × 10^?8T^?1, h'₂ = (-19 ± 2) × 10 ^?8T^?1.     

Study of inclusive neutral current interactions of neutrinos and antineutrinos

We report on results from a study of hadron-energy distributions for ν and $\text{ν}$ inclusive neutral current interactions. There is no significant variation of the neutral to charged current total cross-section ratios R_ν and $\text{R}\text{ν}$ with neutrino energy. The space-time structure of neutral currents is dominated by V?A, with a significant admixture of V+A. The Weinberg-Salam model is in agreement with all data if sin²θ_w=0.24±0.02.     

High-frequency and -field electron paramagnetic resonance of high-spin manganese(III) in axially symmetric coordination complexes

High-frequency and -field electron paramagnetic resonance (HFEPR) has been used to study several complexes of high-spin manganese(III) (3d⁴,S = 2): [Mn(Me₂dbm)X] and [Mn(OEP)X] (X = Cl^?, Br^?), where Me₂dbm^? is the anion of 4,4′-dimethyldibenzoylmethane and OEP^2? is the dianion of 2,3,7,8,12,13,17,18-octaethylporphine. These non-Kramers (integer spin) systems are not EPR-active with conventional magnetic fields and microwave frequencies. However, use of fields up to 15 T in combination with multiple frequencies in the range of 95–550 GHz allows observation of richly detailed EPR spectra. Analysis of the field- and frequency-dependent HFEPR data allows accurate determination of the following spin Hamiltonian parameters for these complexes: [Mn(Me₂dbm)Cl],D = ?2.45(3) cm^?1; [Mn(Me₂dbm)Br],D = ?1.40(2) cm^?1; [Mn(OEP)Cl],D = ?2.40(1) cm^?1; [Mn(OEP)Br],D = ?1.07(1) cm^?1 (E ≈ 0, andg ≈ 2.0 in all cases). Comparison of structural data with the electronic parameters for these and related complexes shows quantitatively the effects of axial and equatorial ligation on the electronic structure of Mn(III). These high-spin complexes can be employed as building blocks in the construction of single-molecule magnets. Thus the accurate determination and understanding of the electronic properties, best obtainable by HFEPR, of these monomeric units is important in understanding and improving the properties of the polynuclear single-molecule magnets which can be formed from them.     

Magnetostriction of hexaferrites in the region of spin-reorientational phase transitions

The temperature dependence of magnetostriction of textured polycrystalline Co_0.72Zn_1.28-W hexaferrite has been studied by means of x-ray dilatometry and strain gauges. It is shown that the magnetostriction constants exhibit an anomalous behavior in the region of spin-reorientational phase transitions and reach as high as 10^?5–10^?4.     

Stoichiometric synthesis of fullerene compounds with lithium and sodium and analysis of their IR and EPR spectra

A modified method is proposed for preparing fullerene compounds with alkali metals in a solution. The compounds synthesized have the general formula Me _n C₆₀(THF)_x, where Me = Li or Na; n=1–4, 6, 8, or 12; and THF = tetrahydrofuran. The use of preliminarily synthesized additives MeC₁₀H₈ makes it possible to prepare fullerene compounds with an exact stoichiometric ratio between C ₆₀ ^n? and Me ⁺. The IR and EPR spectra of the compounds prepared are analyzed and compared with the spectra of their analogs available in the literature. The intramolecular modes T _u (1)-T _u (4) for the C ₆₀ ^n? anion are assigned. The splitting of the T _u (1) mode into a doublet at room temperature for Me _n C₆₀(THF)_x (n=1, 2, 4) compounds indicates that the fullerene anion has a distorted structure. An increase in the intensity of the T _u (2) mode, a noticeable shift of the T _u (4) mode toward the long-wavelength range, and an anomalous increase in the intensity of the latter mode for the Li₃C₆₀(THF)_x complex suggest that, in the fullerene anion, the coupling of vibrational modes occurs through the charge-phonon mechanism. The measured EPR spectra of lithium-and sodium-containing fullerene compounds are characteristic of C ₆₀ ^? anions. The g factors for these compounds are almost identical and do not depend on temperature. The g factor for the C ₆₀ ^n? anion depends on the nature of the metal and differs from the g factor for the C ₆₀ ^? anion.     

Dispersion of dielectric constants in bismuth strontium ferrite (Bi,Sr)FeO<Subscript>3 − <Emphasis Type="Italic">x</Emphasis></Subscript>—Variable-valence perovskite-structure solid solution

The reflection spectrum R(ν) and transmission spectrum Tr(ν) of polycrystalline solid solutions Bi_0.5Sr_0.5FeO_2.75 are studied for the first time using submillimeter and IR spectroscopy in the frequency range 7 < ν < 4000 cm^?1 at temperatures of 10–300 K. A large difference is found between the magnitudes of the dielectric susceptibility measured by contact (at a frequency of 10³ Hz) and noncontact (THz range) methods. It is suggested that powerful relaxation excitations exist at frequencies below 100 cm^?1 (“subphonon” region). The possible origin of the excitations is discussed.     

Study of the R meson produced in 13 GeV/cπ+p interactions

The missing mass spectrum opposite the proton in a 750 000 picture exposure, 13 GeV/cπ⁺p bubble chamber experiment, is investigated in two and four pion channels for structures observed or denied by boson spectrometers at the same energy in the reaction π^?p→X^?p.In the four pion final state the R⁺ enhancement is observed clearly and the possibility of multi-component mass structure is considered. Treating the phenomenon as one object, cross sections and branching ratios are derived for intermediate quasi two and three body decay modes (ωπ, ??, A₂π, ?ππ). The signals in the two pion state and for the neutral state produced opposite Δ⁺⁺(1231) are also presented and an elasticity is calculated.     

Comparative SNMS and SIMS studies of oxidized Ce and Gd

Polycrystalline Ce and Gd surfaces of various oxidation states have been investigated in situ and alternately by Sputtered Neutral Mass Spectrometry SNMS and by SIMS. For the bombardment with 4 keV Ar⁺ ions the dominating peaks in the mass spectra of postionized sputtered neutrals and positive secondary ions refer to metal atoms Me and monoxide molecules MeO. At oxygen concentrations of several atomic percent the sensitivity of SNMS and SIMS are of the same order. Characteristic differences are found between the behaviour of corresponding SNMS and SIMS signals: For SNMS the intensitiesI(MeO⁰) and I(Me⁰) in general vary complementarily when the oxygen is removed from the surface. The intensity ratios $\text{I(MeO}{}^0\text{)}\text{I(Me}{}^0\text{)}$ decrease monotonously by 1 to 2 orders of magnitude. With SIMS both I(MeO⁺) and I(Me⁺) are found to decrease with the oxygen content. The SIMS ratios $\text{I(MeO}{}^{\mathrm{+}}\text{I(Me}{}^{\mathrm{+}}\text{)}$ display an oscillatory behaviour with only little variation of their absolute values. As an example, quantitative results for the behaviour of the ionisation probability α⁺_Me for the secondary ions Ce⁺ and Gd⁺ are derived for low oxygen concentrations.     

Thermoelectric power of (Me4N)2Ag13I15 and (Et4N)2Ag13I15

Thermoelectric power using reversible silver electrodes and electrical conductivity on the compressed pellets of (Me₄N)₂Ag₁₃I₁₅, and (Et₄N)₂Ag₁₃I₁₅ have been measured between room temperature and below 160°C. The results of θ can be expressed by the equations:?θ = 0.115 (10³/T)+0.2905VK^?1 and ?θ = 0.150 (10³/T) + 0.305mV K^?1; and those of conductivity by the equations; σ = 28.7 exp (?0.17eV/kT) ohm^?1cm^?1 and $\text{σ = 216.6 exp (?0.24e}\text{V}\text{kT}\text{)}$ ohm^?1cm^?1; respectively for Me- and Et-electrolytes. The results are discussed and compared with those of previous authors.     

Kinetic energy distributions of neutral In and In2 sputtered by polyatomic ion bombardment

Kinetic energy distributions of neutral In monomers and In₂ dimers sputtered from a polycrystalline indium surface under bombardment with 5 keV/atom Au₁⁻ and Au₂⁻ projectiles have been investigated by means of laser postionization time-of-flight mass spectrometry. Results show that 5 keV Au₁ bombardment leads to results in full compliance with linear cascade sputtering theory. For polyatomic ion bombardment, we find a clear transition to a collisional spike dominated emission process. The spike contribution appears as a low-energy part in the sputtered flux which increases with increasing projectile nuclearity and energy. We show that, the velocity spectrum associated with the low-energy contribution is virtually identical for sputtered monomers and dimers. This finding has important implications with respect to the particle emission mechanism under polyatomic projectile bombardment.     

Fluorescence lifetimes and radiative rate constants of alkanes at 25°C

Fluorescence lifetimes of 33 alkanes were measured at 25°C using a 0.7 ns pulse radiolysis system and the relationship between molecular structure, fluorescence lifetime (τ), quantum yield (Φ_f) and radiative rate constant (R = $\text{Φ}{}_{\mathrm{f}}\text{τ}$) is discussed. The τ's showed a large dependence on the molecular structure, however, the R-values were approximately constant for groups of alkanes: R = 1.3×10⁶s^?1 for n-alkanes, R ≈ 4×10⁶ s^?1 for aliphatic vicinally substituted dimethyl alkanes, R = 7×10⁶s^-1 for cyclohexane and alkylcyclohexanes, and R = 10×10⁶s^?1 for di- and trimethylcyclohexanes. The excited state lifetimes of some non-fluorescing alkanes were also determined from steady-state photolytic quenching data and found to be very low (? 0.3 ns).     

Dynamical study of triplet-triplet energy transfer in rigid solution

Triplet-triplet (T-T) energy transfer from acetophenone to naphthalene-d₈ has been studied in EPA rigid-glass solution at 77 K by masuring the decay of donor phosphorescence and the rise of acceptor T-T absorption over a wide range of time. The results were analyzed in terms of the theory proposed by Inokuti and Hirayama on the basis of a point molecular model. Two parameters, R_O and γ, were determined which are involved in their expression for the rate constant of T-T energy transfer, i.e. n(R) = (1/τ_D) exp[γ(1?R/R_O)], where R and τ_D denote the donor-acceptor distance and the lifetime of donor triplet in the absence of acceptor, respectively. It was found that, in contrast to the Inokuti-Hirayama theory in which γ is assumed to have a constant value, γ increases significantly as the time (t) after flash excitation of the donor becomes smaller: γ ≈ 25 for t/τ_D=10^-2?1, ≈ 35 for t/τ_D = 10^-3? 10^-2, and ≈ 45 for t/τ_D = 10^-4?10^-3. This finding suggests that the true rate constant increases with decreasing R value to a greater extent than the n(R) employed by Inokuti and Hirayama.     

The 2ν1 + ν4 band of carbon tetrafluoride

The 2ν₁ + ν₄ band of ¹²CF₄ at 2445 cm^?1 has been remeasured with a 0.005-cm^?1 resolution by means of a Fourier interferometer. The spectral region investigated here lies between P(70) and R(52). More than 500 line clusters have been assigned. From these a least-squares fit with an overall standard deviation of 0.001 cm^?1 has led to seven significant constants.     

Natural left-right symmetry,atomic parity experiments and asymmetries in high energy e+e− collisions in petra and pep regions

The previously proposed left-right-symmetric SU(2)_L × SU(2)_R × U(1) theory permits one of the two neutral gauge particles N₁ and N₂ to be particularly light (<mW⁺_L) compatible with all neutrin-data and the present atomic parity experiments. Distinguishing features of this theory (with the light mass solution) for e^?e⁺ → μ⁺μ^? and π⁺π^? at PETRA and PEP energies as compared to the SU(2) × U(1) predictions are given.     

Heat capacity of a five-coordinated ferromagnet,chloro bis(N,N-diethyldithiocarbamato)iron(III), in the temperature range from 0.4 to 20 K

The heat capacity of polycrystalline Fe[S₂CN(C₂H₅)₂]₂Cl has been measured in the temperature range from 0.411 to 19.55 K. The transition between ferromagnetic and paramagnetic states is characterized by a sharp λ-type anomaly centered at the Curie temperature, T_c = 2.412 ± 0.008 K. The enthalpy and the entropy of transition are 40.475 J mol^?1 and 11.199 J K^?1mol^?1 (= 1.347 R), respectively. The transition entropy is only 2.81% smaller than R In 4. This fact ascertains that the spin manifold is really a quartet. The ground spin states of the present compound are characterized by a zero-field splitting of the $\text{S =}\text{3}\text{2}$ state into two Kramers' doublets. The overlapping non-cooperative Schottky-type anomaly due to the energy separation between the two Kramers' doublets is separated tentatively from the cooperative heat capacity due to the exchange interaction. Based on a careful analysis of the transition entropy it may be concluded that the magnetic structure of the present complex would be a two-dimensional triangular Ising lattice. The exchange and the Curie-Weiss constants are also determined to be 0.155 and 4.19 K, respectively.     

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.