142,224 research outputs found

    Vibrational state dependence of ionic rotational branching ratios in resonance enhanced multiphoton ionization of CH

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    We show that rapid evolution of a Rydberg orbital with internuclear distance in a resonance enhanced multiphoton ionization (REMPI) process can have a profound influence on the production of molecular ions in alternative rotational states. This is illustrated by calculations of ionic rotational branching ratios for (2+1′) REMPI via the O11 (20.5) branch of the E′ ^2Σ^+(3pσ) Rydberg state of CH. The rotational propensity rule for ionization changes from ΔN=odd (ΔN=N_+−N_i) at lower vibrational excitation, as expected from the ΔN+l=odd selection rule, to ΔN=even at higher vibrational levels. This effect is expected to be quite general and should be most readily observable in diatomic hydrides

    Condensation in ideal Fermi gases

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    I investigate the possibility of condensation in ideal Fermi systems of general single particle density of states. For this I calculate the probability wN0w_{N_0} of having exactly N0N_0 particles in the condensate and analyze its maxima. The existence of such maxima at macroscopic values of N0N_0 indicates a condensate. An interesting situation occurs for example in 1D systems, where wN0w_{N_0} may have two maxima. One is at N0=0N_0=0 and another one may exist at finite N0N_0 (for temperatures bellow a certain condensation temperature). This suggests the existence of a first order phase transition. % The calculation of wN0w_{N_0} allows for the exploration of ensemble equivalence of Fermi systems from a new perspective.Comment: 8 pages with 1 figure. Will appear in J. Phys. A: Math. Gen. Changes (minor): I updated Ref. [9] and its citation in the text. I introduced citation for figure 1 in the tex

    QCD sum rules for the anti-charmed pentaquark

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    We present a QCD sum rule analysis for the anti-charmed pentaquark state with and without strangeness. While the sum rules for most of the currents are either non-convergent or dominated by the DNDN continuum, the one for the non-strange pentaquark current composed of two diquarks and an antiquark, is convergent and has a structure consistent with a positive parity pentaquark state after subtracting out the DNDN continuum contribution. Arguments are presented on the similarity between the result of the present analysis and that based on the constituent quark models, which predict a more stable pentaquark states when the antiquark is heavy.Comment: 19 pages, 8 figures, REVTex, revised version,new figures added and references update

    The false vacuum bubble nucleation due to a nonminimally coupled scalar field

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    We study the possibility of forming the false vacuum bubble nucleated within the true vacuum background via the true-to-false vacuum phase transition in curved spacetime. We consider a semiclassical Euclidean bubble in the Einstein theory of gravity with a nonminimally coupled scalar field. In this paper we present the numerical computations as well as the approximate analytical computations. We mention the evolution of the false vacuum bubble after nucleation.Comment: 23 pages, 12 figures, References added, minor correctio

    Geometrically nonlinear isogeometric analysis of laminated composite plates based on higher-order shear deformation theory

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    In this paper, we present an effectively numerical approach based on isogeometric analysis (IGA) and higher-order shear deformation theory (HSDT) for geometrically nonlinear analysis of laminated composite plates. The HSDT allows us to approximate displacement field that ensures by itself the realistic shear strain energy part without shear correction factors. IGA utilizing basis functions namely B-splines or non-uniform rational B-splines (NURBS) enables to satisfy easily the stringent continuity requirement of the HSDT model without any additional variables. The nonlinearity of the plates is formed in the total Lagrange approach based on the von-Karman strain assumptions. Numerous numerical validations for the isotropic, orthotropic, cross-ply and angle-ply laminated plates are provided to demonstrate the effectiveness of the proposed method

    Coulomb corrections to bremsstrahlung in electric field of heavy atom at high energies

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    The differential and partially integrated cross sections are considered for bremsstrahlung from high-energy electrons in atomic field with the exact account of this field. The consideration exploits the quasiclassical electron Green's function and wave functions in an external electric field. It is shown that the Coulomb corrections to the differential cross section are very susceptible to screening. Nevertheless, the Coulomb corrections to the cross section summed up over the final-electron states are independent of screening in the leading approximation over a small parameter 1/mrscr1/mr_{scr} (rscrr_{scr} is a screening radius, mm is the electron mass, =c=1\hbar=c=1). Bremsstrahlung from an electron beam of the finite size on heavy nucleus is considered as well. Again, the Coulomb corrections to the differential probability are very susceptible to the beam shape, while those to the probability integrated over momentum transfer are independent of it, apart from the trivial factor, which is the electron-beam density at zero impact parameter. For the Coulomb corrections to the bremsstrahlung spectrum, the next-to-leading terms with respect to the parameters m/ϵm/\epsilon (ϵ\epsilon is the electron energy) and 1/mrscr1/mr_{scr} are obtained.Comment: 13 pages, 4 figure

    Giant Shapiro Resonances in a Flux Driven Josephson Junction Necklace

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    We present a detailed study of the dynamic response of a ring of NN equally spaced Josephson junctions to a time-periodic external flux, including screening current effects. The dynamics are described by the resistively shunted Josephson junction model, appropriate for proximity effect junctions, and we include Faraday's law for the flux. We find that the time-averaged IVI-V characteristics show novel {\em subharmonic giant Shapiro voltage resonances}, which strongly depend on having phase slips or not, on NN, on the inductance and on the external drive frequency. We include an estimate of the possible experimental parameters needed to observe these quantized voltage spikes.Comment: 8 pages RevTeX, 3 figures available upon reques
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