Experimental observation of post-collision interaction and interference effects in resonant double photoionization processes

The combined effects of post-collision interaction in the final state and interference due to the indistinguishability of the two electrons have been studied in a selected case of resonant double photoionization of neon. In our coincidence experiments, the photo- and Auger-electron pair was measured when the two electrons have nearly equal energy and are ejected at small mutual angle. The obtained energy distributions exhibit a strong interplay of post-collision interaction and interference effects, in agreement with the theoretical prediction of Sheinerman and Schmidt [J. Phys. B 30, 1677 (1997)] made on beryllium.     

Impact picture in the coulomb interference region at high energies

We present the predictions on pp̄ elastic differential cross sections in the Coulomb interface region for energies 0.546 to 2.0 TeV on the basis of the impact picture.     

Ground-state inversion method applied to calculation of molecular photoionization cross-sections by atomic extrapolation: Interference effects at low energies

The ground-state inversion method, which we have previously developed for the calculation of atomic cross-sections [ 29 ], is applied to the calculation of molecular photoionization cross-sections. These are obtained as a weighted sum of atomic subshell cross-sections plus multi-centre interference terms. The atomic cross-sections are calculated directly for the atomic functions which when summed over centre and symmetry yield the molecular orbital wave function. The use of the ground-state inversion method for this allows the effect of the molecular environment on the atomic cross-sections to be calculated. Multi-centre terms are estimated on the basis of an effective plane-wave expression for this contribution to the total cross-section. Finally the method is applied to the range of photon energies from 0 to 44 eV where atomic extrapolation procedures have not previously been tested. Results obtained for H₂, N₂ and CO show good agreement with experiment, particularly when interference effects and effects of the molecular environment on the atomic cross-sections are included. The accuracy is very much better than that of previous plane-wave and orthogonalized plane-wave methods, and can stand comparison with that of recent more sophisticated approaches. It is a feature of the method that calculation of cross-sections either of atoms or of large molecules requires very little computer time, provided that good quality wave functions are available, and it is then of considerable potential practical interest for photoelectron spectroscopy.     

Coherence effects in inverse bremsstrahlung at high energies

The reaction rate of the inverse bremsstrahlung in crystallic media is calculated. The result of the computations show that enhancement of the reaction rate takes place at certain photon energies due to interference phenomena.     

Dissociation energies of molecular hydrogen and the hydrogen molecular ion

We have obtained improved values for the dissociation energies of molecular hydrogen and its ion by using a high-resolution pulse-amplified laser to probe the second dissociation limit. The onset of the vibrational continuum is observed by state-selective detection of the atomic products of dissociation, and several auxiliary measurements link the results to the ground state. The dissociation energies are accurate to 0.010-0.026 cm(-1), improving previous measurements by a factor of 3-7. Agreement with ab initio calculations is good for H2, D2, and their ions, but not for HD and HD+.     

Coulomb-nuclear interference at sub-Coulomb energies

The Coulomb-nuclear interference pattern in the low-energy heavy-ion excitation of nuclei near closed-shells can be used to investigate the nuclear mass density at large distances, the nature of the effective transition operator and the presence of higher-order direct processes. Semimicroscopic single-folding calculations are compared to low-energy data for ¹⁸O excitation by ²⁰⁸Pb. A strong effect of two-step transfer reactions is predicted in the sub-Coulomb excitation of ¹⁷O by ²⁰⁸Pb.     

Spin effects in hadron scattering at very high energies

In this paper a spin-dependent diffractive model is studied for πN and NN elastic scattering. We find non-trivial results for spin correlation parameters which persist at high energies and have very distinct features in the dip region. It is stressed that these parameters provide good tests of pomeron factorization.     

Spin effects in elastic pp scattering at high energies

A brief survey is made of those popular and recent models of pp-scattering which incorporate spin at least to some extent. These models are: conventional Regge pole models, models of the eikonal type and geometric (optical) models. Particular attention is paid to the structure of polarization to be expected at higher energies.Presented at the Symposium on Hadron-Hadron Scattering at High Energies, Liblice, Czechoslovakia, June 16–21, 1975.     

Dipole model for double meson production in two-photon interactions at high energies

In this work double vector meson production in two-photon interactions at high energies is investigated considering saturation physics. We extend the color dipole picture for this process and study the energy and virtuality dependence of the forward differential cross section. A comparison with previous results is presented, and the contribution of the different photon polarizations is estimated.     

Metastable molecular fluid hydrogen at high pressures

Warm dense hydrogen is studied in the region of fluid–fluid phase transition within the framework of the density functional theory. We report a procedure of obtaining metastable states and calculate the equation of state. Metastable states are diagnosed by pair correlation functions and values of conductivity. We obtain a strong overlapping through the density of metastable and equilibrium branches of pressure isotherms. This indicates the plasma nature of the phase transition.     

Phenomenology of single-spin effects in hadron production at high energies

Within a phenomenological model, experimental data on the transverse single-spin asymmetry (A _N ) and polarization (P _N ) of hadrons are analyzed for 68 different inclusive reactions in hadron-hadron, hadron-nucleus, nucleus-nucleus, and lepton-nucleon interactions. A mechanism that is based on the interaction of the chromomagnetic moment of massive constituent quarks with the effective nonuniform chromomagnetic field of QCD strings formed after the initial color exchange is considered as the origin of single-spin effects. Quark-spin precession in the chromomagnetic field is taken into account. Dynamical masses and anomalous chromomagnetic moments are estimated for constituent u, d, s, c, and b quarks.     

Young's two-slit interference of vector light fields

We explore the peculiar interference behaviors of the vector fields in the Young's two-slit configuration. The interference patterns have a chessboard structure in the middle region and depend on the topological charge and the initial phase of the input vector field. The results have potential applications such as characterizing the topological properties of the arbitrary vector fields.     

The nonlinear effects of quantum electrodynamics at high energies

In this paper we considere ⁺ e ^? scattering with intermediate photon-photon scattering as a possibility for getting information about the nonlinear effects of quantum electrodynamics (QED) at high energies. This process is a higher-order correction to double bremsstrahlung. However, these two processes have quite different behaviour with the photon-photon scattering angle. Here we calculate the unpolarized differential cross section of thee ⁺ e ^? scattering with intermediate γγ scattering and also the interference terms with the double bremsstrahlung. Moreover, we show that the sum of these two contributions predominates over the contribution of the double bremsstrahlung for sufficiently large scattering angles of the photons. This result enables us to extract the differential cross section of the γγ scattering. Through extrapolation to different kinematical conditions we can get the cross sections for nearly real photon-photon scattering, photon splitting and Delbrück scattering. As a quantitative example we use the result for a test of the electron propagator in a gauge-invariant way with the usual minimal interaction. We give also numerical examples of this test, which will improve the present values of the testing parameters.     

Classical stark mixing at ultralow collision energies

Exact solutions of the time-dependent classical equations are obtained for the full array of angular momentum mixing transitions nl-->nl(') in atomic hydrogen induced by collisions with charged particles at ultralow energies. A novel classical expression for the transition probability P(l(')l) is presented. The exact classical results for P(l(')l)(alpha) as a function of l,l(') and the Stark parameter alpha agree exceptionally well with (exact) quantal results. They complement the quantal results by revealing essential characteristics which remain obscured in the quantal treatment.     

Total electron-scattering cross-section for molecular hydrogen at low energies by photoelectron spectroscopy

The relative total electron-scattering cross-section for molecular hydrogen has been measured in the energy region 0.02–1.14 eV. In general the Ramsauer technique is used for such a measurement, but in the present experiment the relative cross-sections have been measured by photoelectron spectroscopy. This is the first time that this technique has been put to such a use. The results in this energy region seem to match better the results of Ramsauer and Kollath than those of Golden et al.     

Low-energy nondipole effects in molecular nitrogen valence-shell photoionization

Observations are reported for the first time of significant nondipole effects in the photoionization of the outer-valence orbitals of diatomic molecules. Measured nondipole angular-distribution parameters for the 3sigma(g), 1pi(u), and 2sigma(u) shells of N2 exhibit spectral variations with incident photon energies from thresholds to approximately 200 eV which are attributed via concomitant calculations to particular final-state symmetry waves arising from (E1)multiply sign in circle(M1,E2) radiation-matter interactions first-order in photon momentum. Comparisons with previously reported K-edge studies in N2 verify linear scaling with photon momentum, accounting in part for the significantly enhanced nondipole behavior observed in inner-shell ionization at correspondingly higher momentum values in this molecule.     

Violation of the Franck-Condon principle due to recoil effects in high energy molecular core-level photoionization

Carbon 1s photoelectron spectra of methane are measured over a photon energy range between 480 eV and 1200 eV. Additional components appear between the individual symmetric stretching vibrational components and are attributed to the excitations of asymmetric stretching and bending vibrations due to recoil of the high-energy photoelectron emission. This recoil effect is the evidence for the violation of the Franck-Condon principle which states that neither the positions nor the momenta of the nuclei change during the ionization event.     

Thermodynamics at high energies

A new thermodynamics, applicable to cosmic ray showers and high-energy physics, is developed. Although all density expressions are unaltered, their global forms are modified due to the new dependence between the volume and the temperature. This occurs in bound systems where the number of particles, instead of being an increasing function of the temperature, is a decreasing one. That certain global expressions for the entropy turn out to be convex functions of the energy necessitates their reinterpretation as the reduction in entropy caused by the volume-temperature constraint. The continuous distribution for the production of hadrons with energies greater than a given amount is shown to correspond to the fact that discrete particle fluctuations follow Poisson's law.