Long-range interaction between Hg*(1,3P1) and noble gas atoms

The long-range, van der Waals interaction is considered for the system M^*(nsnp ^1,3P₁)/noble gas (¹S₀), where M^* is any atom with two valence electrons outside closed shells. An important “correlation” effect is shown to arise due to the different symmetry properties of the spatial parts of the singlet and triplet wavefunctions; this is the direct analogue of the effect of angular correlation in the ground-state problem. Detailed calculations are carried out for Hg^*(6s6p ^1,3P₁) interacting with the noble gases.     

Long-range dispersion interactions involving excited atoms; The H(1s)–H(2s) interaction

The dispersion interaction between two nonoverlapping atoms (or molecules) is expressed in terms of single-atom “polarizabilities.” The formulation is valid even if one atom (or both) is in an excited state. To illustrate the procedure, the dispersion interaction between a 1s and a 2s hydrogen atom is computed accurately through order R^?10 (R = internuclear separation).     

Transitions between the 2s and 2p states of atomic hydrogen in collisions with slow noble gas atoms

The thermal decomposition of diatomic molecules in a light inert gas was examined within the scope of the diffusion theory with allowance for interaction between vibration and rotation. It was shown that molecular rotation changes the value of the dissociation constant within an order of magnitude and appreciably affects its temperature dependence. The results, obtained by computer, can be applied directly to the dissociation of I₂, Br₂, and Cl₂.In conclusion, we express our gratitude to A. I. Vol'pert and L. N. Stesik for the possibility of carrying out the computer calculation.     

Long-range interactions between atoms and molecules

The refractive index data for various gases are fitted to analytical formulae from which may be calculated the coefficient of the leading term of the long-range two-body interactions and the coefficient of the leading term of the long-range non-additive three-body interactions. Coefficients are obtained for mixtures of the gases He, Ne, A, Kr, Xe, H₂, N₂ and CH₄, the probable error being 5%.     

Valence orbital ionization potentials of 1s 22s m2p n atoms and ions

The 2s and 2p valence orbital ionization potentials (VOIP) are determined systematically for atoms and ions with configurations 1s ²2s ^m2p ⁿ , using the Anno-Teruya values of the average energies of the configurations. All the cases with possible values of m and n, in conformity with the Pauli principle, are treated. The 2s or 2p VOIP of a particular ion with the configuration of this type is almost independent of the electron configuration. The VOIP's of an isoelectronic series are fitted to a quadratic equation in terms of atomic number Z: VOIP=A ₀+A ₁ Z+A ₂ Z ², by a least-squares method. There are remarkable regularities among A ₀'s, A ₁'s or A ₂'s, for different isoelectronic series, which may be explained by Slater's simple expression for the total energy of an atom (or ion) with the idea of screening effect due to inner electrons. Various screening constants have been determined from the analysis of such regularities.

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Zusammenfassung Unter Benutzung der Anno-Teruya-Werte für die durchschnittliche Energie der Konfigurationen werden systematisch für Atome und Ionen der Konfiguration 1^{s 2}2s ^m 2p ⁿ die 2s- und 2p-VOIP's bestimmt. Alle FÄlle mit den nach dem Pauli-Prinzip möglichen Werten für m und n werden behandelt. Das 2s- oder 2p-VOIP eines besonderen Ions ist beinahe unabhÄngig von der Elektronenkonfiguration. Nach der Methode der kleinsten quadratischen Abweichung werden die VOIP's einer isoelektronischen Serie mit Hilfe einer in Z (Z=Kernladungszahl) quadratischen Gleichung bestimmt: VOIP=A ₀ +A ₁ Z+A ₂ Z ². Die Koeffizienten A ₀,A₁ und A ₂ zeigen untereinander für verschiedene isoelektronische Serien bemerkenswerte RegelmÄ\igkeiten, die mit der einfachen Slaterformel für die Gesamtenergie eines Atoms oder Ions als Abschirmeffekte der inneren Elektronen erklÄrt werden können. Durch die Untersuchung dieser RegelmÄ\igkeiten konnten verschiedene Abschirmkonstanten bestimmt werden.

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Résumé Les potentiels d'ionisation des orbitales de valence (VOIP) 2s et 2p sont systématiquement déterminés pour les atomes et les ions de configuration 1s ²2s ^m2p ⁿ, en utilisant les valeurs de Anno-Teruya pour les énergies moyennes des configurations. Tous les cas possibles d'après le principe de Pauli sont traités. Le VOIP 2s ou 2p d'un ion donné avec une configuration de ce type est presque indépendant de la configuration électronique. Une relation quadratique en fonction du numéro atomique Z est ajustée pour les VOIP d'une série isoélectronique par la méthode des moindres carrés: VOIP=A ₀+A ₁ Z +A ₂ Z ². Des régularités remarquables se manifestent pour A ₀, A ₁, A ₂ dans différentes séries isoélectroniques; ceci peut Être expliqué à l'aide des expressions simples de Slater pour l'énergie totale d'un atome (ou d'un ion) avec l'idée d'un effet d'écran d aux électrons internes. Différentes constantes d'écran ont été déterminées par l'analyse de ces régularités.

     

Long-range interactions between atoms and charges by double-perturbation treatment

A method of calculating the energy of the long-range interaction between atoms and charges is presented. Simplification of the solution of the perturbation equations is achieved by a formal use of the “Double-Perturbation Method”. Numerical results for the energies of the 2pσ state of HeH⁺² are obtained.     

Systematic determination of the Slater-Condon parameters of atoms and ions with 1s 2 2s m 2p n configurations

Semiempirical values of the Slater parameters F ²(2p,2p) and G ¹(2s, 2p) have been determined for the atoms and ions with the electron configurations 1s ²2s ^m2p ⁿ from the experimental atomic energy levels. Particular attention has been paid to get the values of the parameters to be used for semiempirical calculations on molecular electronic structure. The calculation has also yielded E _av's, the average energies of configurations of these atoms. Evaluation of the semiempirical or effective value of F ⁰ from E of an appropriate electron-transfer reaction, based on the idea presented by Anno [15], is also referred to in the present paper. The semiempirical values of the Slater parameters as well as those of E's and E _av's show almost linear dependence upon atomic number Z through isoelectronic series. From the overall tendency of the correlation lines, it is pointed out that the assignment of atomic energy levels of Na⁵⁺ (1s ²2p ⁴) must be wrong.

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Zusammenfassung Semiempirische Werte der Slater-Parameter F ²(2p,2p) und G ¹(2s, 2p) wurden für die Atome und Ionen mit der Elektronenkonfiguration 1s ²2s ^m2p ⁿ aus den experimentellen atomaren Energietermen bestimmt. Insbesondere wurden die Parameter bestimmt, die für semiempirische Berechnungen der Elektronenstruktur von Molekülen benötigt werden. Die Berechnung ergibt weiterhin Werte von E _av, der Durchschnittsenergie der Konfigurationen der genannten Atome. Die vorliegende Arbeit geht auch auf die Bestimmung des semiempirischen bzw. effektiven Wertes von F ⁰ aus E einer geeigneten Elektronenübertragungsreaktion ein, die auf die Arbeit von Anno [15] zurückgeht. Die semiempirischen Werte der Slater-Parameter sowie der E und E _av zeigen annähernd lineare Abhängigkeit von der Atomnummer Z innerhalb isoelektronischer Reihen. Aus dem Gesamtverhalten der genannten Kurven wird geschlossen, da die Zuordnung der atomaren Energieterme von Na⁵⁺(1s ²2p ⁴) falsch sein dürfte.

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Résumé Détermination à partir des niveaux d'énergie atomiques expérimentaux des valeurs semi-empiriques des paramètres de Slater F ²(2p, 2p) et G ¹(2s, 2p) pour les atomes et les ions ayant les configurations 1s ²2s ^m2p ⁿ. On a fait particulièrement attention d'obtenir les valeurs des paramètres à utiliser pour des calculs moléculaires semi-empiriques. Le calcul a aussi fourni les énergies moyennes des configurations de ces atomes. On évoque aussi le calcul de la valeur semi-empirique ou effective de F ⁰ à partir du E d'une réaction appropriée de transfert électronique, selon une idée de Anno [15]. Les valeurs semiempiriques des paramètres de Slater, ainsi que celles des E et E _moy, montrent une dépendance presque linéaire au nombre atomique Z à travers les séries isoélectroniques. A partir des tendances générales des lignes de corrélation, on remarque que l'attribution des niveaux d'énergie atomiques de Na⁵⁺(1s ²2p ⁴) doit être fausse.

     

Long- and intermediate-range interaction between hydrogen atoms in the B 1Σ state

The energy of the hydrogen molecule in the B ¹Σ state, for internuclear separations 12 ≦ R ≦ 20 a.u., has been computed using an 80-term variational wave function depending explicitly on the interelectronic distance. The same type of wave function has been employed in the perturbation theory approach. Using the polarization approximation, and not expanding the interaction Hamiltonian, the first-, second- and third-order energies have been computed and higher-order corrections have been estimated. The results show that in the region under consideration E and E represent the dominant contributions to the interaction energy in the B state.     

Long-range interaction between heterogeneously charged membranes

Despite their neutrality, surfaces or membranes with equal amounts of positive and negative charge can exhibit long-range electrostatic interactions if the surface charge is heterogeneous; this can happen when the surface charges form finite-size domain structures. These domains can be formed in lipid membranes where the balance of the different ranges of strong but short-ranged hydrophobic interactions and longer-ranged electrostatic repulsion result in a finite, stable domain size. If the domain size is large enough, oppositely charged domains in two opposing surfaces or membranes can be strongly correlated by the electrostatic interactions; these correlations give rise to an attractive interaction of the two membranes or surfaces over separations on the order of the domain size. We use numerical simulations to demonstrate the existence of strong attractions at separations of tens of nanometers. Large line tensions result in larger domains but also increase the charge density within the domain. This promotes correlations and, as a result, increases the intermembrane attraction. On the other hand, increasing the salt concentration increases both the domain size and degree of domain anticorrelation, but the interactions are ultimately reduced due to increased screening. The result is a decrease in the net attraction as salt concentration is increased.     

Long-range interaction at the asymptote 3s+3 of Na2

Vibrational levels a few μeV below the dissociation asymptote 3s + 3p of Na₂ were studied in a molecular beam. The hyperfine structure could be resolved. The molecular levels can be described by adiabatic potentials calculated with the help of atomic parameters: spin-orbit parameter, hyperfine parameter and lifetime of the 3p level. This gives a very precise picture of long oange interactions up to internuclear distances R ≈ 250 Å. Retardation effects were not identified within the error limits of the data in agreement with theoretical estimates. The life-time derived for the 3p level of the sodium atom agrees very well with independent measurements from different methods.     

Mechanism of the formation of hydrogen tetroxide and peroxide via low-temperature interaction between hydrogen atoms and molecular oxygen

A mechanism and kinetic model for the synthesis of peroxide radical condensate via the low-temperature interaction of hydrogen atoms with O₂ molecules is proposed. The main components of the reaction, hydrogen tetroxide H₂O₄ and hydrogen peroxide H₂O₂, are formed in a low-temperature liquid layer formed near the cold surface during synthesis. Molecules of H₂O₄ and H₂O₂ are stabilized by transitioning to the solid phase. The dependences of the \(N_{O_2 } /N_{H_2 O_2 }\) ratio on the ratio of concentrations of H and O₂ in the gas phase, calculated on the basis of the model, are consistent with the experimental data.     

The hyperfine muon-nucleus interaction andP-odd effects in the one-photon 2s → 1s transition of light muonic atoms

The weak interaction of neutral currents of the negative muon and a nucleus results inP-odd correlations in the one-photon 2s → 1s transition of light muonic atoms. If the standard electroweak model is used, the weak mixing of hyperfine components of the μ-atom 2s and 2p 1/2 orbits makes the main contribution to these correlations. A new mechanism of acting the hyperfine structure on theP-odd correlations is considered in the present work. The fact is that the hyperfine muon-nucleus interaction mixes the 2p 1/2 and 2p 3/2 orbits effectively in light muonic atoms whose nuclei have large quadrupole moments. As a result, two new sublevels arise for each of two valuesF _±=(I ± 1/2) of the total angular μ-atom momentum (I is the nuclear spin). The contributions of these sublevels to theP-odd correlations can be comparable with each other. The most strikes manifestation of the given effect occurs for berillium and boron, where the 2s and 2p 3/2 orbits may have close energies. Taking the above effect into account can lead to considerable modification of results against earlier calculations. In particular, theP-odd correlations can vanish and change sign. They can be additionally increased by a factor of several tens.     

Dispersion interaction between helium atoms

Accurate values for the coefficients of the R^?6, R^?8 and R^?10 in the series representation of the dispersion interaction between two helium atoms at distance R are obtained by a simple variation method.     

Linear response theory of the dipole–dipole dispersion interaction between H(1s) atoms

A self-consistent theory of the linear response previously developed by one of us is applied to the dipole–dipole dispersion interaction of two ground state H atoms in the united atom (He) limit, using a Sellmeier representation of the polarizability in terms of pseudostates. Numerical calculations show that a truncated 12-term expansion out of the N = 22 H(1s) dipole pseudospectrum built from STOs with orbital exponent c = 0.985 gives a result exceeding by no more than 5% the variational result for the He dispersion energy.     

(2+1) laser-induced fluorescence of spin-polarized hydrogen atoms

We report the measurement of the spin polarization of hydrogen (SPH) atoms by (2+1) laser-induced fluorescence, produced via the photodissociation of thermal HBr molecules with circularly polarized 193 nm light. This scheme, which involves two-photon laser excitation at 205 nm and fluorescence at 656 nm, offers an experimentally simpler polarization-detection method than the previously reported vacuum ultraviolet detection scheme, allowing the detection of SPH atoms to be performed more straightforwardly, from the photodissociation of a wide range of molecules and from a variety of collision experiments.     

On the photoexcitation of the 2s→2p transition in light muonic atoms

It is known that the energy of the 2s→2p transition of light μ-atoms can be precisely measured by laser spectroscopy. Such measurements provide a good test of quantum electrodynamics predictions. Here we consider how the hyperfine muon-nucleus interaction effects on the photoexcitation of this transition and on the subsequent X-rays emission. Besides the obvious change of the transition energy the hyperfine interaction mixes the 2p 1/2 and 2p 3/2 orbits. This mixing is rather effective in μ-atoms of¹H,⁷Li,⁹Be,¹⁰B and¹¹B. Its taking into account changes the photoexcitation cross-section of electric dipole transitions between the hyperfine components of the 2s and 2p orbits and an angular X-rays distribution as well. These changes prove to be considerable for some transitions. For example, in μ²H and μ⁷Li the cross-section is decreased by factors of two and four respectively. In μ⁹Be it is increased by a factor of two. Moreover, in μ¹H the angular X-rays distribution becomes more anisotropic. Besides the above subject one more question is discussed here. The fact is that the laser experiments can give an information on the residual muon spin polarization at the 2s orbit and on the degree of alignment of the angular μ-atom momentum in this state. The polarization can be determined by measuring an angular correlation between the X-rays emission direction and the momentum of a hard μ-decay electron. The alignment degree can be found by measuring an anisotropy of the angular X-rays distribution.