Interference effects in negative ion formation

We analyze the elastic scattering angular distributions of the16O +16O system at Elab=480 MeV and 704 MeV within the framework of the second-order eikonal model based on Coulomb trajectories of colliding nuclei. The diffractive oscillatory structure observed in the elastic angular distribution could be explained due to the interference between the near- and far-side scattering amplitudes. The presence of a nuclear rainbow in this system is evidenced through a classical deflection function. The effective optical potential is developed from the second-order non-eikonal phase shifts.

The present work deals with the mathematical investigation of some generalizations of Bessel functions. The main motive of this paper is to show that the generating function can be employed efficiently to obtain certain results for special functions. The complex form of Bessel functions is introduced by means of the generating function. Certain enthralling properties for complex Bessel functions are investigated using the generating function method. By considering separately the real and the imaginary part of complex Bessel functions, we get respectively cosine-Bessel functions and sine-Bessel functions for which several novel identities and Jacobi–Anger expansions are established. Also, the generating function of degenerate Bessel functions is investigated and certain novel identities are obtained for them. A hybrid form of degenerate Bessel functions, namely, of degenerate Fubini–Bessel functions, is constructed using the replacement technique. Finally, the explicit forms of the real and the imaginary part of complex Bessel functions are established by a hypergeometric approach.

An inversion procedure to recover the intermolecular potentials from low-energy (4-14 eV) differential scattering data for the systems He${\mathrm{H}}^{+}$, Ne${\mathrm{H}}^{+}$, Ar${\mathrm{H}}^{+}$, and Kr${\mathrm{H}}^{+}$ is presented. The first step in this procedure is to construct the phase shifts {$\ensuremath{\eta}(l)$} from the experimental differential cross section $\ensuremath{\sigma}(\ensuremath{\theta})$ and, for reasons of intuition, the corresponding classical deflection function. This is accomplished by employing a new technique developed recently by Remler which involves singularities in the $S$ matrix. The Remler method is as accurate as, but less cumbersome than, the frequently employed standard partial-wave sum and in addition leads to an intuitive connection between $\ensuremath{\eta}(l)$ and $\ensuremath{\sigma}(\ensuremath{\theta})$. Having found {$\ensuremath{\eta}(l)$}, the intermolecular potential may be determined by means of the transformation method of Vollmer. To test the entire inversion procedure, the intermolecular potential obtained from the ${\mathrm{H}}^{+}$ + He scattering data is compared to the ab initio calculation by Wolniewicz of the ground-state potential for He${\mathrm{H}}^{+}$. This method should be applicable to any spherically symmetric scattering system.

Low energy (0–15 eV) electron stimulated reactions in single 1,2-C2F4Cl2 molecules and clusters

A common environment in which to place Bessel and circular functions is envisaged. We show, by the use of operational methods, that the Gaussian provides the umbral image of these functions. We emphasize the role of the spherical Bessel functions and a family of associated auxiliary polynomials, as transition elements between these families of functions. The consequences of this point of view and the relevant impact on the study of the properties of special functions is carefully discussed.

Methods are derived whereby vibrationally inelastic cross sections may be inverted to obtain a spherically symmetric effective potential (a rotational average of the complete potential) for atom/diatomic collisions. Classical and semi-classical methods are used to obtain inelastic opacity and deflection functions; these are further processed to give particular classical functions which can be evaluated using a small number (⪅ 10) of trajectories. These are then fitted by a parametrized potential function. The methods successfully invert cross sections computed from a known potential. Results of an inversion of experimental vibrationally inelastic scattering data for Li+/H2 are also presented.

Methods are derived whereby vibrationally inelastic cross sections may be inverted to obtain a spherically symmetric effective potential (a rotational average of the complete potential) for atom/diatomic collisions. Classical and semi-classical methods are used to obtain inelastic opacity and deflection functions; these are further processed to give particular classical functions which can be evaluated using a small number (⪅ 10) of trajectories. These are then fitted by a parametrized potential function. The methods successfully invert cross sections computed from a known potential. Results of an inversion of experimental vibrationally inelastic scattering data for Li+/H2 are also presented.

The scattering of N2+ ions by He atoms is studied excluding any electronic excitation. A two centre-screened Coulomb model is taken for the scattering potential. In a first step the classical deflection function is determined for a specific molecular orientation, in assuming that the vibrational and rotational motions are negligible during the collision time. Then the corresponding differential cross section is calculated for an isotropic distribution of the molecular orientations. In a second step the amount of translational energy transferred into the internal degrees of freedom is evaluated and the vibro-rotational dissociation is taken into account. The 'pseudo-elastic' differential cross section is obtained and it is compared to experiment.

This paper addresses the photodetachment dynamics of a negative ion in a time-dependent electric field based on the semiclassical open-orbit theory. The photodetached electron probability density in a real time domain is studied in a gradient electric field for the first time. It is found that because of the influence of the gradient electric field, two or more electron trajectories can arrive at a given point on the detector, and the interference effect between these electron trajectories causes oscillatory structures in the electron probability density. Our calculation results suggest that when the external electric field changes very slowly with time, only two electron trajectories can arrive at a given point on the detector and the electron probability density exhibits a regular two-term oscillatory pattern. However, when the electric field changes quickly with time, four electron trajectories can reach the detector, which makes the oscillatory structures in the electron probability density become much more complicated. In addition, the electric field strength, photon energy, and the position of the detector can affect the electron probability density of this system sensitively. Our study provides a clear and intuitive picture for the photodetachment dynamics of the negative ion in the external electric field from a time-dependent viewpoint and may guide the future experimental researches on the photodetachment microscopy of negative ions in the time-dependent electric field.

Diabetes-induced Alternations in Biomechanical Properties of Urinary Bladder Wall in Rats

We present measurements of differential cross sections and decay asymmetries of incoherent φ‐meson photo‐production from the deuteron at forward angles using linearly polarized photons beam in energy range from the production threshold to E = 2.4 GeV. The experiment was performed at the SPring‐8/LEPS facility. The differential cross section of incoherent production shows a large suppression compared with the free proton case. The reduction for the deuteron cannot be clearly explained in terms of simple isospin asymmetry. The decay asymmetry of incoherent φ photo‐production shows that the eta exchange process is small. Since the exclusive K+K−p cross section shows the same reduction with incoherent, both the proton and neutron cross section reduce similarly. Consequently, the π‐η interference effect is small too. The present results suggest that our understanding of φ photo‐production within a nucleus should be rearranged.

Formation of negative ions via dissociative electron attachment (DEA) to the amino acid serine in the gas phase was studied using two different crossed electron/molecular beam techniques and quantum chemical calculations. Resonance electron capture mass spectrum and effective ion yield curves of 16 negative ions were measured over the electron energy range from close to 0 to 11 eV. The negative ions from serine were detected from resonance states in the vicinity of 0, 1.3, 5, and 8 eV. The dominant reaction channel at low electron energies was (M-H)(-). The relative cross section for this ion exceeds more than 20 times that of any other fragment negative ions. A high-resolution experiment was applied to study fine structures in (M-H)(-) cross section. We have found that the second OH group influences some dissociative channels. Quantum chemical calculations were applied to interpret products of the DEA reaction channels.

To understand the chemical behaviour of lubricant components during boundary lubrication, a general concept of negative ionradical reactive intermediates formation for these components has been proposed. The concept is based upon the ionisation mechanism of these compounds caused by the action of electrons of law energy (1–4 eV). Electrons of such energy (exoelectrons) are spontaneously emitted from most fresh surfaces formed during friction. The principal thesis of the model is that lubricant components form anions which are then chemisorbed on the positively charged areas of rubbing surfaces.The formation of negative ions and their decomposition process are simulated by electron attachment mass spectrography. This type of mass spectrography uses electrons of an energy range similar to those of exoelectrons. The proposed model encompasses the following major stages: (a) low‐energy electron emission process and creation of positively charged spots, (b) action of emitted electrons with lubricant components (anion and radical formation), (c) reactions of anions with metal surfaces forming a film protecting the surface from wear, (d) cracking of chemical bonds producing other radicals. The model explains many lubrication phenomena of hydrocarbons, oxygen‐containing compounds, and many types of chemicals used as antiwear and extreme‐pressure additives.

Local Presynaptic Activity Gates Homeostatic Changes in Presynaptic Function Driven by Dendritic BDNF Synthesis

This paper analyzes the mechanism of non-cavitation tone noise line-spectrum frequency of counter-rotation propeller. The mechanism is interference effect and circumferential harmonics field effect. According to the generalized acoustic analogy equation, the lift and drag which are caused by the mechanism are the source of noise,the far field sound pressure expression is presented. The line-spectrum frequency and the directionality of sound pressure have been analyzed. The results show: the predication line-spectrum frequency could be written as f=sAPF+mBPF1+nBPF2; sound pressure radiation is 8-shaped distribution and the Bessel function's peak condition is a necessary condition for line-spectrum. The counter-rotation propeller's non-cavitation condition is numerically simulated using RNG k-e turbulent model、 sliding mesh model and kFW-H equation. The results shows that RNG k-e Turbulent model has the better accuracy than Realizable k-e turbulent model, and the counter-rotation propeller non-cavitation line-spectrum frequency and the directionality of sound pressure are got by this method which agree well with the result of Academic prediction.