Dirac equation in noncommutative space for hydrogen atom

We consider the energy levels of a hydrogen-like atom in the framework of theta-modified, due to space noncommutativity, Dirac equation with Coulomb field. It is shown that on the noncommutative (NC) space the degeneracy of the levels 2S(1/2), 2P(1/2) and 2P(3/2) is lifted completely, such that new transition channels are allowed. (C) 2009 Elsevier B.V. All rights reserved.

Positronium-hydrogen atom elastic scattering at medium energies

We study the elastic scattering of positronium atoms by hydrogen atoms at medium energies using partial-wave Born-Oppenheimer (BO) exchange amplitudes and report accurate BO cross sections in the energy range 0 to 60 eV. The present BO results agree with a 22-state R-matrix and a five-state coupled-channel model potential calculation, but disagree strongly with a conventional close-coupling calculation as well as its input BO amplitudes at medium energies.

Positronium-hydrogen-atom scattering in a five-state model

The scattering of orthopositronium (Ps) by hydrogen atoms has been investigated in a five-state coupled-channel model allowing for Ps(1s)H(2s,2p) and Ps(2s,2p)H(1s) excitations using a recently proposed electron-exchange model potential. The higher (n greater than or equal to 3) excitations and ionization of the Ps atom are calculated using the first Born approximation. Calculations are reported of scattering lengths, phase shifts. elastic, Ps and H excitation, and total cross sections. Remarkable correlations are observed between the S-wave Ps-H binding energy and the singlet scattering length, effective range, and resonance energy obtained in various model calculations. These correlations suggest that if a Ps-H dynamical model yields the correct result for one of these four observables, it is expected to lead to the correct result for the other three. The present model, which is constructed so as to reproduce the Ps-H resonance at 4.01 eV, automatically yields a Ps-H bound state at - 1.05 eV that compares well with the accurate value of - 1.067 eV. The model leads to a singlet scattering length of 3.72a(0) and effective range of 1.67a(0), whereas the correlations suggest the precise values of 3.50a(0) and 1.65a(0) for these observables, respectively. [S1050-2947(99)07703-3].

Convergent variational calculation of positronium-hydrogen-atom scattering lengths

We present a convergent variational basis-set calculational scheme for elastic scattering of the positronium atom by the hydrogen atom in S wave. Highly correlated trial functions with appropriate symmetry are needed to achieve convergence. We report convergent results for scattering lengths in atomic units for both singlet (= 3.49 +/-0.20) and triplet (= 2.46 +/-0.10) states.

Low-energy correlations in the positronium-hydrogen-atom system

Employing a nonlocal model potential for electron exchange we study positronium-hydrogen-atom (Ps-H) scattering using a five-state coupled-channel model allowing for Ps(2s,2p)H(1s) and Ps(1s)H(2s,2p) excitations. We find remarkable correlations among S-wave Ps-H binding energy, scattering length, effective range, and resonance energy in the electronic singlet state. Using these correlations we predict fairly accurate values of singlet Ps-H scattering length (3.50a0) and effective range (1.65a0).

Differential cross sections for elastic and inelastic positronium-hydrogen-atom scattering

A time reversal symmetric regularized electron exchange model was used to elastic scattering, target elastic Ps excitations and target inelastic excitation of hydrogen in a five state coupled model. A singlet Ps-H-S-wave resonance at 4.01 eV of width 0.15 eV and a P-wave resonance at 5.08 eV of width 0.004 eV were obtained using this model. The effect on the convergence of the coupled-channel scheme due to the inclusion of the excited Ps and H states was also analyzed.

Hydrogen atom in space with a compactified extra dimension and potential defined by Gauss' law

We investigate the consequences of one extra spatial dimension for the stability and energy spectrum of the non-relativistic hydrogen atom with a potential defined by Gauss' law, i.e. proportional to 1 /| x | 2 . The additional spatial dimension is considered to be either infinite or curled-up in a circle of radius R. In both cases, the energy spectrum is bounded from below for charges smaller than the same critical value and unbounded from below otherwise. As a consequence of compactification, negative energy eigenstates appear: if R is smaller than a quarter of the Bohr radius, the corresponding Hamiltonian possesses an infinite number of bound states with minimal energy extending at least to the ground state of the hydrogen atom.

The Hydrogen Atom: The Bohr Model in Detail

The Bohr Model for the Hydrogen Atom's electron is discussed in detail, with a recapitulation of angular momentum and a detailed discussion of relevant units (out of the cgs system).

Advanced Physical Chemistry Problems (II), Hydrogen Atom and Hyrdrogen Molecular Ion

Slightly advanced problems in Physical Chemistry, herein concerning the H-atom and the Hydrogen Molecular Cation, are presented and discussed.

Alternative Formulations for Angular Momentum Operators, Cartesian and Spherical Polar Forms

The conversion between representations of angular momentum in spherical polar and cartesian form is discussed.

Symmetry in chemistry from the hydrogen atom to proteins

The last 2 decades have seen discoveries in highly excited states of atoms and molecules of phenomena that are qualitatively different from the “planetary” model of the atom, and the near-rigid model of molecules, characteristic of these systems in their low-energy states. A unified view is emerging in terms of approximate dynamical symmetry principles. Highly excited states of two-electron atoms display “molecular” behavior of a nonrigid linear structure undergoing collective rotation and vibration. Highly excited states of molecules described in the “standard molecular model” display normal mode couplings, which induce bifurcations on the route to molecular chaos. New approaches such as rigid–nonrigid correlation, vibrons, and quantum groups suggest a unified view of collective electronic motion in atoms and nuclear motion in molecules.

Insights into hydrogen atom adsorption on and the electrochemical properties of nitrogen-substituted carbon materials

The nitrogen substitution in carbon materials is investigated theoretically using the density functional theory method. Our calculations show that nitrogen substitution decreases the hydrogen adsorption energy if hydrogen atoms are adsorbed on both nitrogen atoms and the neighboring carbon atoms. On the contrary, the hydrogen adsorption energy can be increased if hydrogen atoms are adsorbed only on the neighboring carbon atoms. The reason can be explained by the electronic structures analysis of N-substituted graphene sheets. Nitrogen substitution reduces the pi electron conjugation and increases the HOMO energy of a graphene sheet, and the nitrogen atom is not stable due to its 3-valent character. This raises an interesting research topic on the optimization of the N-substitution degree, and is important to many applications such as hydrogen storage and the tokamaks device. The electronic structure studies also explain well why nitrogen substitution increases the capacitance but decreases the electron conductivity of carbon electrodes as was experimentally observed in our experiments on the supercapacitor.