Optical Interaction Potentials Research Articles

а- бөлшектердің 9Be ядросымен соқтығысу кезіндегі серпімді шашырауының жаһандық заңдылықтары

The article investigates the characteristics of the experimental data of the elastic scattering cross section in the low-energy range of the a+9Be nuclear system. General regularities depending on the change in the energy of accelerated ions of the parameters of the obtained cross sections are established. Based on the analysis in the framework of the optical model (OM), energy-dependent optical interaction potentials in a wide range of energies were found.The energy regularity of potentials, revealed as a result of systematic analysis, makes it possible to predict with sufficient accuracy the cross-section of processes at energies at which experimental measurements were not carried out.The potential, which is a complex function of the interaction between nuclei, is an empirical measurement that describes the interaction in the scattering process.Studies of the dependence of the potential on external factors should be carried out individually for each nuclear system. Such analyses carried out in order to improve the accuracy of phenomenological theories should be based on a large array of experimental data. To clarify the truthfulness of the results of phenomenological approaches, it would be theoretically more correct to determine the global patterns of potentials and energy dependences of the full reaction cross-section.The article defines the energy dependence of the potentials and the total cross-section of the reaction based on a systematic analysis of the experimental data set in the energy range of laboratory Elab=30 - 60 MeV for the α+9Be process.Optimal values of the cross-section parameters satisfying global laws depending on the energy of the accelerating beam are found.

The topology of the reaction stereo-dynamics in chemi-ionizations

Details on the stereo-dynamic topology of chemi-ionizations highlight the role of the centrifugal barrier of colliding reactants: it acts as a selector of the orbital quantum number effective for reaction in a state-to-state treatment. Here, an accurate internally consistent formulation of the Optical interaction potentials, obtained by the combined analysis of scattering and spectroscopic experimental findings, casts light on structure, energy and angular momentum couplings of the precursor (pre-reactive) state controlling the stereo-dynamics of prototypical chemi-ionization reactions. The closest approach (turning point) of reagents, is found to control the relative weight of two different reaction mechanisms: (i) A direct mechanism stimulated by exchange chemical forces mainly acting at short separation distances and high collision energy; (ii) An indirect mechanism, caused by the combination of weak chemical and physical forces dominant at larger distances, mainly probed at low collision energy, that can be triggered by a virtual photon exchange between reagents.

Synthesizing variable particle interaction potentials via spectrally shaped spatially coherent illumination

Collective scattering of spatially coherent radiation by separated point emitters induces inter-particle forces. For particles close to nano-photonic structures as, for example, nano-fibers, hollow core fibers or photonic waveguides, this pair-interaction induced by monochromatic light is periodic and virtually of infinite range. Here we show that the shape and range of the optical interaction potential can be precisely controlled by spectral design of the incoming illumination. If each particle is only weakly coupled to the confined guided modes the forces acting within a particle ensemble can be decomposed to pairwise interactions. These forces can be tailored to almost arbitrary spatial dependence as they are related to Fourier transforms with coefficients controlled by the intensities and frequencies of the illuminating lasers. We demonstrate the versatility of the scheme by highlighting some examples of unconventional pair potentials. Implementing these interactions in a chain of trapped quantum particles could be the basis of a versatile quantum simulator with almost arbitrary all-to-all interaction control.

Study of high-lying cluster states of nuclei by the method of particle–particle angular correlations

The current status of research on nuclear reactions induced by light and semiheavy ions of energy up to 10 MeV/nucleon on light and intermediate nuclei by measurement of the angular correlation functions of the final products is reviewed. The principal theoretical and experimental studies on particle–particle correlations carried out in recent years are analyzed. The methods of calculating the angular correlation functions and the spin tensors of the reaction-product density matrix for reactions involving excited states using the distorted-wave method with finite interaction range and the modified compound-nucleus model are described. The α−d and α−t correlations in reactions involving 6,7 Li and 14 N ions are analyzed. The highly excited α-cluster states in 12 C , 16 O , 20 Ne , and 24 Mg are studied. The polarizationtensors of the 6 Li nucleus in the 3 + state are calculated and compared with experiment. It is shown that the particle–particle angular correlation functions and the polarizationtensors can provide unique information about the reaction mechanism and about the structure of the wave functions of highly excited nuclear states, including the nature of the radial dependence in the interior of the nucleus and the optical interaction potentials in the entrance and exit reaction channels, and so on. This review can be useful for both theoreticians and experimentalists working on the physics of nuclear reactions involving particles of moderate energy.

Optical interaction potentials from differential cross section measurements at thermal energies. III. He(21S)+Na

For pt.II see ibid., vol.10, no.4, p.695 (1977). Differential cross sections have been measured for He(21S)+Na at five different kinetic energies between 52 and 207 meV. For the lowest kinetic energy a backward glory is observed. An optical potential is obtained from a simultaneous fit to the data at all energies. A modified Morse potential with a well depth of epsilon =300 meV and a minimum distance of rm=6.3 au gives the best fit. The well depth is in good agreement with data from Penning electron spectroscopy, but the total ionisation cross section is larger than that determined earlier. The metal beam is generated in a recirculating supersonic oven.

Optical interaction potentials from high-resolution differential cross section measurements at thermal energies II. He(21S) + Ar

For pt.I see ibid., p.2693 (1976). Differential cross sections for He(21S)+Ar have been measured for six relative kinetic energies between 21 and 180 MeV. At low kinetic energies the small-angle oscillations are clearly resolved. Except for the lowest energy (21 MeV) a well resolved rainbow peak is observed in the differential cross sections. The real and imaginary parts of the interaction potential are obtained from the data. The real part has an intermediate maximum in the potential ( Delta E=25 MeV, rmax=7 au) which causes the rainbow peaks. The imaginary part can be expressed by an exponential plus a Gaussian. The velocity dependence of the total and ionization cross sections is calculated and the possibility of an energy-dependent width of the potential is indicated.

Optical interaction potentials from high-resolution differential cross section measurements at thermal energies. II. He(21S)+Ar

For pt.I see ibid., p.2693 (1976). Differential cross sections for He(21S)+Ar have been measured for six relative kinetic energies between 21 and 180 MeV. At low kinetic energies the small-angle oscillations are clearly resolved. Except for the lowest energy (21 MeV) a well resolved rainbow peak is observed in the differential cross sections. The real and imaginary parts of the interaction potential are obtained from the data. The real part has an intermediate maximum in the potential ( Delta E=25 MeV, rmax=7 au) which causes the rainbow peaks. The imaginary part can be expressed by an exponential plus a Gaussian. The velocity dependence of the total and ionization cross sections is calculated and the possibility of an energy-dependent width of the potential is indicated.

Optical interaction potentials from differential cross section measurements at thermal energies. I. He(23S)+Ar

Differential cross sections for He(23S)+Ar have been measured in the relative kinetic energy range from 20 to 480 meV. At low kinetic energies the small-angle oscillations have been resolved, so that it was possible to derive an accurate complex or optical interaction potential. The velocity dependence of the ionization and total cross sections calculated from this optical potential is in good agreement with experimental results. Orbiting resonances are predicted at low velocities. The derived potential is unusually soft for large internuclear distances, where the argon atom penetrates only the diffuse He(2s) orbital. The repulsion becomes much harder when the argon atom starts to overlap the He(1s) orbital.