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1.
Experimental differential cross sections for 40 keV electrons scattered by C2H2, C2H4 and C2H6 molecules were measured using the gas electron diffraction method in the range of the scattering variable s from s = 1 A?1 to s = 30 A?1. The differential cross sections for neon were also measured and compared with calculated differential cross sections to calibrate the diffractograph. Experimental differential cross sections show significant deviations with respect to theoretical differential cross sections calculated from the Debye-Ehrenfest model, mainly in the range of small scattering angles. The observed differences are connected to chemical binding effects. From the experimental data, an estimation of the binding energy was carried out. The deduced values: ?0.58 ± 0.20 au for C2H2, ?0.94 ± 0.30 au for C2H4 and ?1.23 ± 0.40 au for C2H6 are in agreement with those obtained by thermochemical methods.  相似文献   

2.
Angle-resolved translational energy spectroscopy has been applied to Cs4I + 3 ions that survived 8 keV collisions with a range of collision gas targets, including inert gases and deuterium. The experimental data comprise values of the translational energy loss ΔTR as a function of the (laboratory-frame) scattering angle θ R for each collision gas under conditions such that single-collision events dominated the scattering. The values of ΔTR increase with θ R, in accordance with very general expectations. However for any value of θ R, the values of ΔTR for helium and deuterium as targets were almost indistinguishable from one another but were at least five to six times larger than those for neon and all other collision gases. These data have been shown to be consistent with theoretical considerations based upon conservation of energy and linear momentum. Theoretical approaches include the simple “elasticlimit” model, which makes no mechanistic assumptions, and a particular “binary-model” theory, which excludes electronic excitation as a possibility. Both theories are consistent with the experimental data and interpret the surprisingly large values of ΔTR for low-mass targets in terms of large recoil energies of the target required to ensure conservation of momentum. The most likely alternative candidate as sink for ΔTR is internal excitation of the target, but this possibility was excluded in the present work by choosing ΔTR values less than the lowest excitation energies of the inert gas targets. Moreover, such an interpretation cannot explain the similar results obtained using helium and deuterium, which were markedly different from those obtained for all other collision gases.  相似文献   

3.
Published results of vapour—liquid and vapour—solid equilibrium studies for neon—krypton and neon—oxygen mixtures have been analysed to give values for the interaction second virial coefficients. B12. Comparisons are made with other results for the NeKr system and with the predictions of some proposed intermolecular potentials.  相似文献   

4.
The emission spectrum and the formation kinetics of NeF* is studied using two different excitation techniques. Bye-beam excitation of a Ne/F2 mixture the yield was found to be low having a maximum at 0.2 hPa of F2 and at a low neon pressure of less than 0.2 MPa. An ion exchange reaction between Ne+ and RbF leading to NeF* was initiated by irradiation of a mixture of neon and RbF vapor using an argon-ion beam. TheDX transition of NeF* was observed at 107.0 nm, theBX transition at 108.8 nm. The kinetics of the reactions are discussed.  相似文献   

5.
Corrections to the third virial coefficient derived from the first-order three-body exchange forces, ΔC1(T), in helium, neon and argon have been calculated. Inclusion of ΔC1 and the corrections due to the non-exchange three-body forces leads to a satisfactory agreement with experimental data.  相似文献   

6.
We report on measurements of Stark widths and shifts of four prominent Ne I lines of the 3s,3s′-3p transition arrays. The measurements were performed in an atmospheric-pressure arc discharge operated in argon–neon gas mixture.Sub-Doppler degenerate four-wave mixing technique was used to measure the line profiles, while Thomson scattering yielded the plasma parameters: electron density, ne = (0.53–1.33) × 1023 m 3, and electron temperature, Te = 10,200–20,900 K. The measured profiles are symmetric within the uncertainty limits. The experimental Stark widths and shifts are compared with results of other experiments and theoretical calculations.  相似文献   

7.
Ab-initio computations at the STO-3G level have been performed on CO2-Ne. The short-range interactions are roughly proportional to Σiri?12, where the ri are the distances from neon to the atoms in CO2. In this empirical approximation, the anisotropy effects are conveniently revealed by the proportionality coefficient whose value depends on the angle between the OCO and C-Ne axes.  相似文献   

8.
The dispersion energy between two neon and two argon atoms is computed from an ab initio perturbative procedure not based on the multipole expansion. A comparison with the multipole expansion provides C6 = 5.36 for Ne and 76.6 for Ar. It is seen that one d polarization function provides the main part of the C6R?6 contribution, the exponent of this function probably being related to the polarizability of the molecule. The multipole expansion seems acceptable up to the van der Waals minimum but quite invalid for smaller distances, and doubtful at the van der Waals minimum itself.  相似文献   

9.
Elastic photon scattering and absorption in the vicinity of core atomic orbital energies give rise to resonances in the elastic photon scattering cross-section. Of interest is whether a dilute-ion aqueous system provides an environment suitable for testing independent particle approximation (IPA) predictions. Predictions of the energy of these resonances have been determined for a Dirac–Slater exchange potential with a Latter tail. At BM28 (ESRF), tuneable X-rays were obtained at eV resolution using a 1 1 1 Si monochromator. From target systems including Cu2+ and Zn2+, the X-rays were scattered through high angle from an aqueous medium contained in a thin Perspex cell provided with 8 μm kaplan windows. An energy resolution of ∼500 eV from the HPGe detector was adequate to separate the elastic scattering signal from Kα radiation but not from Compton or Kβ contributions. The Compton contribution from the medium was removed assuming validity of the relativistic impulse approximation. The contribution due to Kβ fluorescence and the resonant X-ray Raman scattering process were handled by assuming the branching ratio for Kα and Kβ contributions to be constant and to be accurately described by fluorescent yields measured above edge. At ionic concentrations ranging from 0.01 to 0.1 mol/l, resonance structures accord with predictions of elastic scattering cross-sections calculated within IPA. Amplitudes calculated using modified form-factors and anomalous scatter factors computed from a Dirac–Slater exchange potential were convolved with a Lorentzian of several eV (FWHM).  相似文献   

10.
On-line two-angle (15° and 90°) light scattering measurements with a gel permeation chromatography for linear and branched polystyrene in tetrahydrofuran (a good solvent) and in trans-decalin (a theta solvent) were made and compared with data from a multi-angle light scattering detector and literature values. Theoretically, weight-average molecular weight and the radius of gyration Rg can be determined accurately in the range where Rg2k2 is less than 1.2 (rod)∼1.7 (random coil); here, k is the absolute value of the scattering vector for a right angle detector with the Berry square root method. Molecular weight dependence of the radius of gyration obtained from the two-angle light scattering detector for linear and branched polystyrenes under different thermodynamic conditions were measured and found to be almost the same as values measured with a multi-angle light scattering detector and literature values in the appropriate range of molecular weight.  相似文献   

11.
Irradiation of gaseous discharges with a tunable laser produces easily observed voltage changes at wavelengths which correspond to electronic transitions for species in the discharge. This work reports observations made in the 572–654 nm region on a neon glow discharge, which is operated at 5 torr (670 Pa) pressure and 2–25 mA current. A wide variety of absorption transitions have been detected which originate in the 1sn (3P2,1,0, 1P1) and 2pn excited states. The resulting voltage signals are both positive and negative, and some transitions exhibit sign changes as a function of discharge current. Some of the results can be interpreted in terms of processes which directly affect the neon metastable atom concentration (3P2, 3P0) and states also produce voltage changes which can be explained in terms of processes which either enhance or decrease ionization.  相似文献   

12.
The delayed X-ray and electron emission from metastable states in fast, foil excited neon ions has been investigated. High resolution X-ray and electron spectroscopy at calibrated relative detection efficiencies was applied to determine fluorescence yields for the radiative decay of the (1s2s2p)4P J 0 , J=1/2, 3/2, 5/2 states in NeVIII. Using measured total lifetimes corrected for cascading effects the forbidden radiative and autoionization rates were determined.  相似文献   

13.
The scattering of X-rays from biological samples has been shown to produce characteristic profiles, which depend on their molecular structure. The highly ordered fat molecules in an adipose tissue result in a relatively sharp scattering peak at 1.1 nm?1 with a scattering profile, which is considerably different from the scattering profile of a water-rich tissue. The latter is characterized by a broad scattering peak at about 1.6 nm?1. A biological sample consisting of a mixture of both adipose and a water-rich tissue is expected to show a scattering profile, which is directly linked to the relative contribution of each component and would reflect the percentage by volume of each component in the mixture. In this work, X-ray scattering profiles of a number of dairy products and water are measured. The values of two selected X-ray scattering characterization parameters (I1/I2% and areas A1/A2% of the scattering peaks at 1.1 and 1.6 nm?1, respectively) are plotted against the fat content of each of the measured dairy samples. Results show a strong linear dependence of each of the X-ray scattering parameters and the fat content of the investigated dairy products. These results suggest a possible use of such technique as a new, simple and straight forward method for determination of fat content of dairy products that would join and support the currently available techniques.  相似文献   

14.
Gas-phase 21Ne nuclear magnetic resonance spectra were measured at the natural abundance of 21Ne isotope for samples consisting of pressurized neon up to 60 bar at room temperature and applying the magnetic field of the strength B0 = 11.7574 T. It showed that the nuclear magnetic resonance frequency is linearly dependent on the density of gaseous neon. The resonance frequency was extrapolated to the zero-density point, and it permitted the determination of the 21Ne nuclear magnetic moment, μ(21Ne) = 0.6617774(10) μN. The present value of μ(21Ne) is not influenced by the bulk magnetic susceptibility of neon and interactions between neon atoms; therefore, it is more precise and reliable than the previous result obtained for μ(21Ne).  相似文献   

15.
The scattering of He atoms from liquid He n -clusters withn=10 to 1000 at energies between 0.01 and 5.0 meV has been investigated by calculating integral cross sections for elastic scattering, absorption scattering and vibrational excitation of the liquid drop vibrations using a hard core potential, a transparent core potential, a black core and an optical model potential. The implications for planned scattering experiments are discussed.  相似文献   

16.
The vibrational dephasing rate is calculated for H2-rare gas mixtures between 85 and 300 K. The semiclassical calculation which only considers unbounded trajectories is based on binary interaction of particles through a Lennard—Jones potential. A comparison is made with three-dimensional and with collinear results obtained when a purely repulsive potential is considered. It is shown that the temperature dependence of the vibrational dephasing rate increases monotonically as T rises. Experimental investigation of Q1 (1) Raman lines for n-H2 perturbed by neon, argon and krypton between 100 and 300 K has been realized. The comparison between calculated and measured linewidths suggests that bounded states have to be taken into account at the lowest temperatures considered here.  相似文献   

17.
The reactions of laser‐ablated Au, Ag, and Cu atoms with F2 in excess argon and neon gave new absorptions in the M? F stretching region of their IR spectra, which were assigned to metal‐fluoride species. For gold, a Ng? AuF bond was identified in mixed neon/argon samples. However, this bonding was much weaker with AgF and CuF. Molecules MF2 and MF3 (M=Au, Ag, Cu) were identified from the isotopic distribution of the Cu and Ag atoms, comparison of the frequencies for three metal fluorides, and theoretical frequency calculations. The AuF5 molecule was characterized by its strongest stretching mode and theoretical frequency calculations. Additional evidence was observed for the formation of the Au2F6 molecule.  相似文献   

18.
Due to the forward peaked differential cross section for elastic atom—atom scattering the effect of multiple collisions has to be considered in the analysis of crossed beam measurements of the total cross section and especially of the small angle differential cross section at large values of the beam attenuation. At angles θ ≈ θ0, with θ0 the quantum mechanical scaling angle of the elastic differential cross section, the correction for the latter case amounts to 20% at beam attenuations I/I0 = exp(?1). Firstly, a careful analysis of the probabilities for single and multiple scattering is given, resulting in an expression for the measured beam signals which is correct for all values of the beam attenuation. The probability for multiple scattering is then calculated for an inverse power potential V(r) = ?Csr?s, with s = 4 through s = 7, which include both the case of ion—atom scattering (s = 4) and atom—atom scattering (s = 6). The results are given as effective differential cross sections σn(θ) for n-fold scattering. They are described by a single, simple analytical function with four free parameters that have been determined for n = 2, 3 and 4 by a least squares method. The σn(θ) are normalised to the total cross section Q.  相似文献   

19.
K X-ray satellite spectra produced during the bombardment of uranium with 500 MeV neon, have been investigated with a high resolution crystal spectrometer. The experimental results are compared with theoretical predictions for vacancy production computed in the semiclassical separate atom perturbation theory and corrected forL subshell coupling and electron transfer from targetL shell into projectileK shell. The agreement between theory and experiment is rather good. It turns out, that the reduction ofL vacancy production due toL subshell coupling is essentially compensated by theL electron transfer from target to projectile. The present work is an extension of a previous study of theK α1 satellite spectra of tantalum bombarded with 403 MeV nitrogen.  相似文献   

20.
Infrared spectra of monomeric oxalic acid-h2, -hd and -d2 have been observed using neon matrix-isolation spectroscopy. In addition, spectra of oxalic acid-h2, vapor were obtained using a heated absorption cell with a 10 m pathlength. All IR active fundamentals are assigned for oxalic acid-h2, and -d2, except the low frequency torsion. The spectra are interpreted in terms of the C2h intramolecularly hydrogen bonded model. Two vibrational assignments are discussed; one involves a very large intensity for the v8 + v11 (COH torsion) combination band of oxalic acid-h2. Tentative values for several Raman active fundamentals of oxalic acid-h2 are suggested using possible combination bands. Few fundamentals of oxalic acid-hd correlating with the Raman modes of the symmetric monomers could be observed. A force constant analysis of the by secular block is presented.  相似文献   

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