Particle Mass Spectra Research Articles

Metal‐Metal Coordination Chemistry: Free Clusters of Group 12 Elements with Sodium

AbstractA systematic study of the mass spectra of particles formed in a supersonic nozzle expansion of Zn, Cd, and Hg vapors together with Na was performed. The particles discussed in this paper contain only one heavy atom and less than 12 Na ligands. Mass spectra from the neutral particles were generated by photoionization at five wavelengths (250, 260, 280, 300, and 320 nm) with a slit width corresponding to 16.5 and 3.3 nm, respectively. The abundances were corrected to relative differential ionization cross‐sections. Photoionization potentials for Nan M with 5 < n < 10 and M = Zn, Cd, Hg were measured. Below n = 6 no mixed clusters were found. The first abundance maximum occurred for all M at n = 8. A second maximum was with n = 16 or n = 18 (not covered in this paper). This selectivity can be rationalized by recent ab initio calculations by Fantucci et al. (J. Chem. Phys.; in press) and by jellium calculations, which give a closed shell at n = 8 with the occupations 1s21p62s2. Ionization potentials clearly show a level reversal to 1p‐2s‐1d in contrast to the homonuclear jellium with 1p‐1d‐2s. This is similar to previous results with KnMg (Kappes, M. et al., Chem. Phys. Lett., 1985, 119: 11). Molecular dynamics simulations with empirical potentials show that the heavy metal migrates to the center of a cube in the frozen asymptote of NagM. At finite temperatures and for larger central atoms, a square antiprismal arrangement seems to be more stable.

Source Apportionment of Individual Carbonaceous Particles Using14C and Laser Microprobe Mass Spectrometry

An exploratory study of laser microprobe mass spectra of individual atmospheric soot particles has been made in search of a potential combustion source tracer index. A tentative “cluster ratio index” (CRI = C4 −/C2 −) has been found and compared with bulk measurements of 14C in a set of ambient samples exhibiting varying impacts from woodburning and motor vehicle exhaust. A CRI-14C calibration curve resulted, and it led to the conclusion that, at the present level of precision, three particles (or agglomerates) of micrometer size or about 3 pg of carbon would be required for discrimination between the two pure sources. Mixture samples, such as those reported here, would require about 40 times as much. Classification of small set of individual particles from the mixed source ambient samples, suggests preservation of carbonaceous source identity at the single particle level.

A SU(7)×SU(7) Preon model

We propose a SU(7)×SU(7) preon model which obeys both the 'tHooft anomaly-matching and decoupling conditions, and contains four generations of leptons and quarks. The mass spectrum of particles is obtained to be consistent with experiments via three dynamical symmetry breaking steps.

On the mass spectrum of elementary particles

A simple theory of the elementary particle mass spectrum is proposed. It originates from the Dirac idea of the free electron motion and from the transformed Klein-Gordon equation. The theory is based on an equation that includes the squared mass operator having an infinite sequence of orthogonal eigenfunctions and a discrete spectrum of eigenvalues. A discrete mass formula is derived. It yields values of mass that are in agreement with present-day empiric data for elementary particles.

Laboratory and in-situ analysis of comet dust

Comets are primitive, kilometer-sized bodies that formed in the outer regions of the solar system. Composed of ice and dust, comets are generally believed to be relic building blocks of the outer solar system that have been preserved at cryogenic temperatures since the formation of the Sun and planets. The analysis of cometary material is particularly important because the properties of cometary material provide direct information on the processes and environments that formed and influenced solid matter both in the early solar system and in the interstellar environments that preceded it.The first direct analyses of proven comet dust were made during the Soviet and European spacecraft encounters with Comet Halley in 1986. These missions carried time-of-flight mass spectrometers that measured mass spectra of individual micron and smaller particles. The Halley measurements were semi-quantitative but they showed that comet dust is a complex fine-grained mixture of silicates and organic material. A full understanding of comet dust will require detailed morphological, mineralogical, elemental and isotopic analysis at the finest possible scale. Electron microscopy and related microbeam techniques will play key roles in the analysis. The present and future of electron microscopy of comet samples involves laboratory study of micrometeorites collected in the stratosphere, in-situ SEM analysis of particles collected at a comet and laboratory study of samples collected from a comet and returned to the Earth for detailed study.

Dust coma structure of comet Halley from SP-1 detector measurements

The SP-1 detectors aboard the Vega 1 and Vega 2 spacecraft measured the spectral and spatial distributions of dust grains, with the aim of investigating the dust release process and other properties of the comet nucleus1–3. The dust particle mass spectra do not exhibit the expected low-mass cutoff4 at 10−14 g; instead, they continue to rise to ∼10−16 g. The apex of the dust paraboloid resulting from scattering of sunlight is estimated to lie at a distance of 40–45×103 km from the nucleus, although there is a small number density of particles well beyond this boundary. Particles of mass 10−12–10−14 g are relatively depleted at large distances from the nucleus, due to stronger light scattering by these particles. Strong inhomogeneity of the dust number density suggests the existence of a sunward-pointing cone of enhanced dust emission, of width 70–80°. The spatial dispersion of a narrow dust jet has been used to estimate the sense and period of rotation of the nucleus and the approximate azimuthal location of the jet source, as well as the mass-dependent velocity dispersion of the dust particles.

中性粒子の質量および運動エネルギースペクトルと高分解能収束性飛行時間分析装置

中性粒子の質量および運動エネルギースペクトルと高分解能収束性飛行時間分析装置

Composite Nambu-Goldstone superfield in a nonlinear interaction model- mass spectrum of the model

A mass spectrum of composite particles is studied in a supersymmetric (SUSY) composite model with nonlinear interactions of the F-type, which are taken to be invariant under SO(2, C). Composite particles are conatined in a massive superfield and a massless Nambu-Goldstone superfield associated with spontaneous breakdown of SO(2, C). Through explicit SUSY- and SO(2)-breaking, a massless Nambu-Goldstone boson (NGB) and quasi Nambu-Goldstone fermion (QNGF) acquire masses, which are estimated to be: M NGB 2⋍M SS M CS and M QNGF ⋍M SS M CS /M (M SS ≪M CS ≪M by the use of Dashen's formula, where M SS is an SO(2)-singlet SUSY-breaking scale; M CS is a supersymmetric SO(2)-breaking scale; M is the mass of the massive superfield.

Low-energy predictions of a two-loop finite supersymmetric SU 5 theory

We present a detailed discussion of a two-loop finite supersymmetric SU 5 theory, with particular emphasis on the new particle mass spectrum and its dependence on the input parameters. The model predicts sin 2 θ w = 0.237, m b/ m τ ≈ 1.8 (at M W) and M X = 5.3 × 10 15 GeV, which means that nucleon decay, if observable, will be to strange final states. We find in general m g > m q > m e , and that results consistent with a supersymmetric explanation of the CERN monojet and “top-quark” events are possible, in which case we predict light (O(20 GeV)) charged scalar leptons.

Sputtering properties of copper-lithium alloys at reactor-level temperatures and surface erosion rates

Previous experiments on copper-lithium alloys at temperatures up to 250 °C and with erosion rates of 0.01–0.1 monolayer/s for 3 keV Ar+ bombardment have shown that in the electric and magnetic field environment of a magnetic-confinement fusion reactor, it is possible to maintain a lithium overlayer which will significantly reduce the copper erosion rate. We have extended these experiments to the reactor-relevant regime of 350–400 °C, with erosion rates approaching one monolayer/s (1.5 keV Ar+ bombardment at 2.1× 1014/cm2s., normal incidence). By comparison with the lower-fluxexperiments, it is found that radiation damage effects start to dominate both the surface concentration and depth profile of the lithium. The subsurface region of enhanced lithium concentration is broadened, while the surface concentration is not depleted as rapidly per incident ion as in the low-flux case. The time-dependent lithium depth profile is calculated using a computer code developed at Argonne which includes both Gibbsian segregation and radiation-induced effects. The experimental results are compared with these calculations. It is found that the sputtering behavior of the copper-lithium alloys is highly dependent on the mass and energy spectrum of the incident particles, the sample temperature, subsurface structure, and the partial sputtering yields of the alloy components.

Analysis of individual biological particles by mass spectrometry

A method has been developed for the measurement of the mass spectrum of single biological particles introduced in aerosol form into a quadrupole mass spectrometer. The aerosol is generated by nebulizing an ethanol suspension of bacteria. The particles are injected in the form of a beam into the mass spectrometer where they are individually volatilized by impaction on a rhenium filament and ionized by electron bombardment. The average intensity of a mass peak is obtained from the pulse height distribution of about a thousand ion pulses from different particles. Results are reported for Pseudomonas putida, Bacillus cereus and Bacillus subtilis. The results for Pseudomonas putida and Bacillus subtilis are comparable with the data reported in the literature [8,10]. However, peaks at higher masses in the present work are found to be more intense, probably because of the difference in the pyrolysis conditions. Significant differences between the relative intensities of mass peaks in the spectra from the two species are found. This may provide a method for differentiation between different micro-organisms.

Mass spectra of vector particles in D = 11 supergravity compactified on a squashed seven-sphere

We evaluate all spectra of the vector harmonics on a squashed seven-sphere in the manifestly SO(5) × SU L(2) covariant formalism.

Ion-induced chemistry in condensed gas solids

Solids of H 2O, D 2O, CO 2, and SO 2 have been bombarded by MeV and keV ions, and the sputtering of these materials investigated by measuring the total yield and the mass and energy spectra of ejected particles. One observes the results of considerable chemical activity in these low temperature solids. With MeV ions incident on D 2O and CO 2, the production of D 2, O 2 and CO, O 2 respectively are found, while keV ions on SO 2 produce SO, SO 3 and O 2.

Stellar evolution in N-body simulations of disk galaxies. I

The Kalnajs (1972, 1976) Omega models of global mass and velocity distributions are employed in the present two-dimensional N-body simulation, which allows for a spectrum of particle masses, stellar explosions, explosion remnant interactions with an interstellar medium, and the creation of new stars from the gas. Two sequences of runs using the Omega values of 0.8 and 0.9 examine the separate and combined effects of particle mass distribution, the gravitational influence of an interstellar gas distribution on the N-body particles, and stellar evolution, allowing for stellar explosions and star formation from the gas. It is found that both Omega values' nonequilibrium results dramatically change when evolution is allowed to occur. These results call for more realistic coupled N-body and evolution simulations in order to improve the understanding of disk galaxy evolution.

Analytic solutions in the theory of coagulating systems with sinks

Analytic solutions are derived for the problem of the evolution of the mass spectrum of three models of coagulating systems with three-dimensional uniform sinks. The case when the rate of drainage of particles with masses greater than some critical value G is higher compared with the rate of an individual act of coalescence is considered, and the problem is reduced to the consideration of a coagulation process without sinks, but where coagulation of particles of mass greater than G is forbidden. Coagulation kernels that are a) independent of the mass of the colliding particles, b) proportional to the sum, and c) equal to the product of masses of colliding particles are considered. Exact expressions are obtained for the dependence of the coagulating particles mass spectrum and for the sediment, and their asymptotic form in the limit when G is large is analyzed.

Particle charge interchange during acceleration in flare regions

We have examined the conditions for the establishment of charge equilibrium of solar particles during their acceleration. We derive criteria for charge interchange with the atomic and ionized hydrogen at the particles'sources, for two different acceleration mechanisms. It is found that charge interchange is established whenever a particle event is produced. The implications related to mass and charge spectra of particles are discussed. The measured charge state of solar particles cannot in general be directly used for diagnosis of the source temperature, so we suggest another alternative based on the emitted radiation from electron capture.

Predictions and measurements of mass spectra of the charged nucleonic component of cosmic rays at mountain altitude

A cosmic-ray mass spectrometer utilizing a superconducting magnet, digitized wire spark chambers, and time-of-flight scintillation counters has examined the mass spectrum of low-momentum charged particles at 2750-m altitude (747 g/cm/sup 2/). For the first time at mountain altitude, the deuteron spectrum has been clearly resolved. The proton results confirm earlier work. The data indicate the presence of a few /sup 4/He nuclei. Upper limits are given to fluxes of antiproton and hypothetical massive particles in the 5-to-10-GeV/c/sup 2/ range. The low-momentum deuteron spectrum, as well as the proton spectra at various atmospheric depths, can be well understood in terms of a cosmic-ray atmospheric cascade calculation. The deuterons are principally produced by N+N..-->..d+..pi.. and quasielastic nucleon scattering on n-p pairs within the nucleus. Calculations are also presented of the expected intensities of low-momentum antiprotons and hypothetical massive particles at mountain altitude.

Field-flow fractionation of alkali-liberated nuclear polyhedrosis virus from gypsy moth Lymantria dispar linnaeus

Rod-shaped viral particles of the gypsy moth nuclear polyhedrosis virus (NPV) were obtained through alkaline dissolution of inclusion bodies isolated and purified from infected hosts. The liberated viral fraction contains a wide assortment of enveloped aggregated forms as well as enveloped monomers. This complex mixture was separated by means of sedimentation field-flow fractionation (sedimentation FFF) to give a mass spectrum of the separated particles. From the elution pattern effective molecular weights could be assigned to the various resolved components. Through electron microscopy it was possible to characterize the components as monomers, dimers, etc. In parallel experiments the same viral mixture was separated by the more commonly used density gradient sedimentation technique. The two methods are compared as to time and convenience of manipulation, as well as to the amount of physicochemical information that can be extracted from each separation. The mixture of aggregate viral structures was dialyzed against a nonionic detergent solution. Sedimentation FFF of the dialysate revealed a uniform population of non-enveloped particles with an effective molecular weight which was lower than that of the initial monomer fraction. Electron microscopic observations confirmed that this lower molecular weight fraction did indeed contain rod-like structures which were thinner than the initial enveloped monomers indicating that most if not all of the enveloped material had been removed from the viral rod structures.

Models for SU(N) ×SU(N) symmetry breaking with extremum constraints

The extremum properties of some functions defined on the compact groups or their representations are investigated. The extremum constraints for the vacuum expectation value of U(N) ×U(N) and SU(N) ×SU(N) ⧠ [Z2(P) ×Z2(C)] symmetry breaking perturbation Hamiltonian are used to determine the models compatible with nonnegative particle mass spectrum in the first perturbation order. Some model‐independent properties inferred by extremum constraints of chiral and CP‐symmetry breaking are also examined.

Nonlocal structures: Bilocal photon

As a starting point, it is postulated that all particles and fields are built from a single primitive field, which must then be a massless fermion with a σ spin of one-half. Two helicities are embodied in a τ spin of one-half. The vacuum is an open Fermi sea whose height is a wave number κ. Elementary particles are structures having the form of standing-wave systems floating on the vacuum sea, with the height κ providing both the scale of inner structural size and the mass unit for the elementary particle mass spectrum. A bilocal photon starts with a function describing two primitive quanta with parallel σ spin and opposite τ spin. A centroid-time wave equation then couples-in an infinite set of orthogonal functions. The introduction of an operatorQλ permits the reduction of the infinite secular determinant to a finite six-by-six determinant. Solutions (for the infinite expansion) are obtained describing photons with right-handed and left-handed polarizations. Superpositions of these give linearly polarized photons. Electric and magnetic field vectors, satisfying the vacuum Maxwell equations, are obtained from a bilocal Hertz vector given by п= (2/κ3c)(∂/∂tr)∇rΨ(1,2), where Ψ(1,2) is the bilocal wave function, and tr and r are the relative time and relative position variables.