Rectification of the dipole force in a monochromatic field created by elliptically polarized waves

The rectification of the force of induced light pressure in laser fields formed by elliptically polarized running waves in zero magnetic field is considered. Explicit analytic expressions for the induced and spontaneous forces of light pressure exerted on a stationary atom are obtained for two classes of closed optical transitions: J _g=J→J _e=J+1 and J _g=J→J _e=J (J is half-integral), where J _g and J _e are the total angular momenta of the ground and excited energy levels. It is shown that the ellipticity of waves is the necessary condition for the emergence of the rectification of the induced force in a monochromatic field. The optimal parameters of the field and the maximum rectification coefficient are calculated for a number of optical transitions. The dependence of the rectified force on the velocity is investigated analytically and numerically for the simplest 1/2→1/2 transition.     

Chiral spin liquid in a two-dimensional helical XY magnet with two chiral order parameters

The critical properties of an XY helimagnet on a square lattice with two chiral order parameters are studied by Monte Carlo simulations. This model is a modification of the J ₁-J ₂-J ₃ model with J ₂ = 0. The case of different third range order interactions J ₃ are considered, J ₃ ^a ?? J ₃ ^b . A first order transition is found away from the Lifshitz points 4J ₃ ^a = J ₁ and 4 J ₃ ^b = J ₁. It is pointed out that a chiral spin liquid phase possibly exists near the Lifshitz points.     

Steady-state light-induced forces in atomic nanolithography

An analysis of general characteristics of light-induced forces is presented for arbitrary monochromatic masks in which optical pumping of atoms and spontaneous emission play an important role. Dependence of regions of localization on detuning and ellipticity is determined for cyclic transitions of two types: J å J with half-integer J and J å J + 1 with arbitrary J. Numerical simulations of atomic beam focusing with one-and two-dimensional light masks show that spatial atom distributions with narrow features and high contrast can be formed in dissipative masks. In particular, spherical aberration is substantially reduced when the pumping field is tuned to a J å J + 1 transition with large J in lin ～ lin configuration as compared to nondissipative masks.     

Manifestation of higher polarization moments in the dipole emission under conditions of stepwise excitation and anisotropic collisions

The induction of higher polarization moments-the octupole orientation and the hexadecapole alignment—in the case of two-step excitation of atoms through dipole transitions and their manifestation in the polarization of dipole emission under conditions of anisotropic collisions are studied. For all channels of the two-step excitation process J ₀→J ₁ J, the efficiencies of production of higher polarization moments with integer and half-integer angular momenta from J=2 to J=7 through the absorption of linearly or circularly polarized light are calculated. The rates of collisional relaxation and interconversion of higher polarization moments, for both orientation and alignment, as functions of frequency detuning of the laser line from the center of the Doppler profile are calculated. The theory is illustrated by an example of two channels of excitation of the atomic state J=2 by circularly polarized light: J ₀=0→J ₁=1J=2 and J ₀=3→J 1=2 (or 3)→J=2. In the first case, the octupole orientation enhances or attenuates the signal of circular polarization depending on the laser frequency detuning. In the second case, it represents the only source producing orientation and circular polarization of the emitted light.     

Dependence ofJ/Ψ suppression in heavy ion collisions on total transverse energy,nucleon numbers andJ/Ψ transverse momentum

We present a set of semiquantitative predictions for the behaviour ofJ/Ψ suppression in heavy ion collisions as a function of the total transverse energy, nucleon numbers of colliding ions and theJ/Ψ transverse momentum. These predictions are based on the assumption that all ofJ/Ψ suppression is due toJ/Ψ and χ disintegrations in collisions with hadrons in a dense hadronic gas formed in the heavy ion collisions. The hydrodynamic evolution of the hadron gas is taken into account. The onset of the quarkgluon plasma formation should manifest itself by clear qualitative deviations fromJ/Ψ suppression calculated in this way, in particular as thresholds or kinks in theE _T -dependence, or as a threshold forJ/Ψ suppression as a function of the atomic number of the target, expected a Cu or below.     

General results on glueball masses in QCD

A number of authors have investigated mass inequalities for mesons and baryons in QCD. These provide rigorous non-perturbative constraints on the mass spectrum. Similar inequalities for glueballs are investigated. For nonzero spin J, in the large-N_c approximation, m_J⁻⩾m_J⁺ is found. (For J = 0, the existence of a gluon condensate can modify this statement.) There are also constraints on how fast m_J can grow with J. For example, for m_J = a + bJ^α, 0 ⩽ α ⩽ 1 is found, a result consistent with Regge behaviour.     

Phase diagrams of competing quadruple and binary interactions on Cayley tree-like lattice: Triangular Chandelier

We study the phase diagrams for the Ising model on a Cayley tree-like lattice, called Triangular Chandelier, with competing nearest-neighbour interactions J₁, prolonged next-nearest-neighbour interactions J_p and one-level next-nearest-neighbour quadruple interactions J_l1. The phase diagrams display the multicritical points (the Lifshitz points) that are at nonzero temperature and many modulated phases. To perform this study, an iterative scheme similar to that appearing in real space renormalization group frameworks is established; it recovers, as particular case, previous work of Vannimenus extension result given by Ganikhodjaev and U?uz for k=3. At vanishing temperature, the phase diagram is fully determined for all values and signs of J₁,J_p and J_l1. At finite temperatures several interesting features are exhibited for typical values of J_l1/J₁ and −J_p/J₁.     

Formation of Stripes and Slabs Near the Ferromagnetic Transition

We consider Ising models in d = 2 and d = 3 dimensions with nearest neighbor ferromagnetic and long-range antiferromagnetic interactions, the latter decaying as (distance)^?p , p > 2d, at large distances. If the strength J of the ferromagnetic interaction is larger than a critical value J _c , then the ground state is homogeneous. It has been conjectured that when J is smaller than but close to J _c , the ground state is periodic and striped, with stripes of constant width h = h(J), and h → ∞ as \({J\to J_c^-}\) . (In d = 3 stripes mean slabs, not columns.) Here we rigorously prove that, if we normalize the energy in such a way that the energy of the homogeneous state is zero, then the ratio e ₀(J)/e _S(J) tends to 1 as \({J\to J_c^-}\) , with e _S(J) being the energy per site of the optimal periodic striped/slabbed state and e ₀(J) the actual ground state energy per site of the system. Our proof comes with explicit bounds on the difference e ₀(J)?e _S(J) at small but positive J _c ?J, and also shows that in this parameter range the ground state is striped/slabbed in a certain sense: namely, if one looks at a randomly chosen window, of suitable size ? (very large compared to the optimal stripe size h(J)), one finds a striped/slabbed state with high probability.     

Monte Carlo simulation of the three-dimensional XY model with bilinear–biquadratic exchange interaction

The three-dimensional XY model with bilinear–biquadratic exchange interactions J and J′, respectively, has been studied by Monte Carlo simulations. From the detailed analysis of the thermal variation of various physical quantities, as well as the order parameter and energy histogram analysis, the phase diagram including two different ordered phases has been determined. There is a single phase boundary from a paramagnetic to a dipole–quadrupole ordered phase, which is of second order in a high J/J′ ratio region, changing to a first-order one for 0.35⩽J/J′⩽0.5. Below J/J′=0.35 there are two separate transitions: the first one to the quadrupole long-range order (QLRO) phase at higher temperatures, followed by another one to the dipole–quadrupole long-range order (DLRO) phase at lower temperatures. The finite-size scaling analysis yields values of the critical exponents for both the DLRO and QLRO transitions close to the values for the conventional XY model which includes no biquadratic exchange.     

Theoretical ab initio calculation of the indirect nuclear spin-spin coupling constants of monohetero cyclopropanes and cyclopropenes via the equations-of-motion method

Nonempirical calculations using the equations-of-motion approach, which includes the main portion of electron correlation effects, are reported for the one-bond coupling constants in the three-membered rings borirane, cyclopropane, azirane, oxirane, silirane, phosphirane, and thiirane and related double-bond analogs. The important overall result is that the ¹J(CC) and ¹J(CC) constants are spread over broad ranges, much wider in the case of the double-bond species, with a nearly regular increase with the electronegativity of the central heteroatom. For the boron cycles the smallest ¹J(CC)'s are predicted, with ¹J(CC) surprisingly lower than ¹J(CC). This exceptional pattern is accounted for in terms of the peculiar electronic structure of these rings formed by the electron-deficient B atom. The ¹J(Heteroatom-C), ¹J(Heteroatom-H) and ¹J(CH) couplings correlate correctly with the available experimental data.     

A microscopic analysis of moments of inertia

A microscopic analysis of moments of inertia is performed within the cranked Nilsson model. Special emphasis is put on the second-derivative moment of inertia, J⁽²⁾. Contributions to this from changes of rotational frequency and deformation are separately discussed. A simple expression for the latter is derived and it is for a studied series of Yb isotopes usually found to contribute with less than 10% to the total J⁽²⁾ value. J⁽¹⁾, J⁽²⁾ and J_rigid are calculated as functions of spin at the appropriate equilibrium deformations for the even-even nuclei ^160–176Yb. Variations of J⁽²⁾ with particle number and spin are discussed. Relations between J⁽²⁾ and the deformation are studied in detail, especially in connection with the super-backbending.     

Phase diagram of the two-dimensional Ising model with random competing interactions

An Ising model with ferromagnetic nearest-neighbor interactions J₁ (J₁>0) and random next-nearest-neighbor interactions [+J₂ with probability p and −J₂ with probability (1−p); J₂>0] is studied within the framework of an effective-field theory based on the differential-operator technique. The order parameters are calculated, considering finite clusters with n=1,2, and 4 spins, using the standard approximation of neglecting correlations. A phase diagram is obtained in the plane temperature versus p, for the particular case J₁=J₂, showing both superantiferromagnetic (low p) and ferromagnetic (higher values of p) orderings at low temperatures.     

Vacancy-vacancy and vacancy-electron interactions in TiOx

Quantitative measurements have been made of the diffuse scattering from TiO_x, single crystals with both quenched specimens and specimens at high temperatures above the ordering reaction. These measurements indicate that there are strong vacancy-vacancy interactions in the fifth and sixth neighbor shell around a vacancy (J₅ and J₆). Also there is evidence for scattering due to the Fermi surface which arises from vacancy-electron interactions (J′), not phonon-electron interactions. The energies of these interactions have been measured: J₅ ? 4 meV, J₆ ? 9 meV. J′ ? 70 meV. These interactions exhibit correlation lengths of the order of 8 nm.     

Relativistic corrections to quantum mechanical concept ofJ/ψ formation time

The effect ofJ/ψ dissolution in quark-gluon plasma is calculated within quantum mechanical approach taking into account also relativistic corrections. It is found that relativistic effects do not influence significantly the time dependence of theJ/ψ dissolution. Consequently the rate ofJ/ψ suppression is not dramatically changed.     

Hadronic gauge couplings in meson decays

The branching ratiosR(J→ππρ)≡Γ(J→ππρ)/Γ(J→ππ) for naturalJ ^P mesons have been evaluated under the assumption that theT(J→ππρ) amplitudes are generated by the gauge principle for ρ-mesons originally proposed by Sakurai in his approach to VMD. The ratios are predicted to increase withJ and are compatible with the present-day data. This suggests that the hadronic interactions of the photon proceed exclusively through its hadronic (VMD) component.     

Mj-selection rule of rotational energy transfer

Inelastic collisional processes like the changing of the rotational stateJ of diatomic molecules are accompanied by a change of the pertinent Zeeman quantum numberm _J. as well. Changes of them _J-state have a strong bearing on orientation and alignment transfer whose experimental proof has been given previously by McCaffery et al. In this paper a model is proposed which describesm _J selection in accordance with Grawert's general considerations. The model succeeds in explaining Brunner's experimental result that the total transfer rate from J to \(\bar J\) is inversely proportional to 2J+1 and proportional to 2J _< + 1.J _< being the minimum ofJ and \(\bar J\) .     

Phase transitions and critical properties of the frustrated Heisenberg model on a layer triangular lattice with next-to-nearest-neighbor interactions

The critical behavior of the three-dimensional antiferromagnetic Heisenberg model with nearest-neighbor (J) and next-to-nearest-neighbor (J ₁) interactions is studied by the replica Monte Carlo method. The first-order phase transition and pseudouniversal critical behavior of this model are established for a small lattice in the interval R = |J ₁/J| = 0?C0.115. A complete set of the main static magnetic and chiral critical indices is calculated in this interval using the finite-dimensional scaling theory.     

Can the incident photo-to-electron conversion efficiency be used to calculate short-circuit current density of dye-sensitized solar cells

The relationship between the integration of the incident photo-to-electron conversion efficiency (IPCE) and the measured short-circuit current density (J_SC) of dye-sensitized solar cell (DSC) has been analyzed. The J_SC of DSC under full sun is usually considered to be determined by the overlap between its spectral IPCE and the spectral photon flux incident on the cell. However, the IPCE spectrum has been found to be influenced by the bias light intensity in many practical cases. Through theoretical deduction, we have proved that J_SC calculated from IPCE spectrum is related to the slope at corresponding incident light intensity on the short-circuit photocurrent density–incident light intensity (J_SC?E_light) curve. The equal relation between J_SC calculated from IPCE and J_SC practically measured can only be obtained when the J_SC?E_light curve is a straight line through the origin of the coordinates. The measured results of four DSC samples with different working condition show a good agreement with the theory. In addition, a simple method to validate the accuracy of IPCE measurement is also demonstrated.     

On the concept of theJ/gy formation time in quark-gluon plasma

We analyze the rate with which theJ/ψ content of an originally narrow wave packet of charmed quark-antiquark pair is diminishing in a medium which screens colour charges. TheJ/ψ content decreases to 50% within a typical time of 0.2–0.3 fm. Taking this into account, we find thep _T -dependence ofJ/ψ suppression by quark-gluon plasma to be much flatter than in simplified calculations based on the semi-classical picture ofJ/ψ formation time.     

The microscopic Interacting Boson Model for nondegenerate orbits

The microscopic Interacting Boson Model formalism is outlined and a general procedure is described for deriving the parameters of the model when the valence orbits are nondegenerate. This latter technique involves expanding pair creation operators for J = 0 (or J = 2) correlated pairs in terms of J = 0 (or J = 2) pair creation operators for individual orbits. This expansion enables us to relate matrix elements for the multi-orbit problem to matrix elements for individual orbits for which the well-known Racah-seniority reduction formulae apply. Our calculated results for the parameters of the boson-boson quadrupole-quadrupole interaction show a definite relationship to the underlying subshell structure of each major shell, in agreement with the phenomenological results. It is also discovered that the results obtained using particle states are not the same as those obtained using hole states, due to the truncation scheme used to extablish the correlated J = 0 and J = 2 pairs.