Two-neutrino positron double-beta decay of <Superscript>106</Superscript>Cd for the 0<Superscript>+</Superscript> → 0<Superscript>+</Superscript> transition

The two-neutrino positron double-beta decay of ¹⁰⁶Cd for the 0 ⁺ 0⁺ transition has been studied in the Hartree-Fock-Bogoliubov model in conjunction with the summation method. In the first step, the reliability of the intrinsic wave functions of ¹⁰⁶Cd and ¹⁰⁶Pd nuclei has been tested by comparing the theoretically calculated results for yrast spectra, reduced B(E2: 0⁺ 2⁺) transition probabilities, quadrupole moments Q(2⁺) and gyromagnetic factors g(2⁺) with the available experimental data. In the second step, the nuclear transition matrix element M₂ and the half-life T_1/2² for the 0 ⁺ 0⁺ transition have been calculated with these wave functions. Moreover, we have studied the effect of deformation on the nuclear transition matrix element M₂.     

Decays of baryon resonances into ΛK<Superscript>+</Superscript>, ΣK<Superscript>+</Superscript> and Σ<Superscript>+</Superscript>K<Superscript>0</Superscript>

Cross-sections, beam asymmetries, and recoil polarisations for the reactions γp → K ⁺Λ;γp → K ⁺Σ⁰, and γp → K ⁰Σ⁺ have been measured by the SAPHIR, CLAS, and LEPS Collaborations with high statistics and good angular coverage for centre-of-mass energies between 1.6 and 2.3 GeV. The combined analysis of these data with data from π and η photoproduction reveals evidence for new baryon resonances in this energy region. A new P₁₁ state with mass 1840 MeV and width 140 MeV was observed contributing to most of the fitted reactions. The data demand the presence of two D₁₃ states at 1875 and, optimistically, at 2170 MeV.     

The evaluation of the branching ratios of the decays φ(1020)→2π<Superscript>+</Superscript>2π<Superscript>−</Superscript>π<Superscript>0</Superscript>, π<Superscript>+</Superscript>π<Superscript>−</Superscript>3π<Superscript>0</Superscript>

Combining the Okubo-Zweig-Iizuka rule in the decay φ→ρπ→π⁺π^?π⁰ with the ρ→4π decay amplitudes, we calculate the φ→2π⁺2π^?π⁰ and φ→π⁺π^?3π⁰ ones. The partial widths of the above φ decays are evaluated, and the excitation curves in e⁺e^? annihilation are obtained, assuming reasonable particular relations among the parameters characterizing the anomalous terms of the HLS Lagrangian. The evaluated branching ratios B_φ→π⁺_π^?_3π⁰ ≈ 2 × 10^?7 and B_φ→2π⁺_2π^?_π⁰ ≈ 7 × 10^?7 are such that, with the luminosity L=500 pb^?1 attained at DAΦNE φ factory, one may already possess about 1685 events of the decays φ→5π.     

(EC + β<Superscript>+</Superscript>) decays of the 11/2<Superscript>-</Superscript> isomer and 1/2<Superscript>+</Superscript> ground state of <Superscript>143</Superscript>Dy

The 1/2⁺ ground state and a 11/2^- isomer of very neutron-deficient isotope ¹⁴³Dy were produced by irradiation of an enriched target of ¹⁰⁶Cd with ⁴⁰Ca and studied by using a helium-jet fast tape-transport system in combination with proton-γ, X-γ and γ-γ coincidence measurements. A simple ( EC + β⁺) decay scheme of ^143mDy with a half-life of 3.0(3) s and a tentative ( EC + β⁺) decay scheme of ^143gDy with a half-life of 5.6(10) s are proposed. As a by-product, the 347- and 545-keV γ transitions in ¹³⁸Sm following the β-delayed proton emission of ¹³⁹Gd decay and the 323-keV γ transition in ¹³⁹Eu following the β-delayed proton emission of ¹⁴⁰Tb decay could be observed for the first time. Received: 20 August 2002 / Accepted: 28 October 2002 / Published online: 11 February 2003 RID="a" ID="a"e-mail: xsw@ns.lzb.ac.cn Communicated by D. Schwalm     

Emission spectroscopy of the A<Superscript>1</Superscript>Π–X<Superscript>1</Superscript>Σ<Superscript>+</Superscript> system of AlH

The high-resolution emission spectrum of the A¹ Π–X¹Σ⁺ transition of AlH was observed in the 18 000–25 000 cm^-1 spectral region using a conventional spectroscopic technique. The AlH molecules were excited in an Al hollow-cathode lamp filled with a mixture of Ne carried gas and a trace amount of NH₃. The emission from the discharge was observed with a plane grating spectrograph and recorded by a photomultiplier tube. In total 163 transition wave numbers belonging to six bands (0-0,1 and 1-0,1,2,3) were precisely measured and rotationally analysed. In the final fit the present data have been combined with available high-resolution measurements of the vibration-rotation bands by White et al. [J. Chem. Phys. 99, 8371 (1993)]. This procedure enabled extracting molecular constants for the A¹ Π and X¹ Σ⁺ states of AlH. A very slight local perturbation has been discovered in the v=1 vibration level of the A¹ Π state at J=5. This was probably caused by the interaction with the a³Π state.     

Charge transfer in energetic Li<Superscript>2+</Superscript>–H and He<Superscript>+</Superscript>–He<Superscript>+</Superscript> collisions

The total cross sections for charge transfer in Li²⁺-H and He⁺-He⁺ collisions have been calculated, using the four body first Born approximation with correct boundary conditions (CB1-4B) and four body continuum distorted wave method (CDW-4B) in the energy range 10–5000 keV/amu. The role of dynamic electron correlations is examined as a function of the impact energy. The present results call for additional experimental data at higher impact energies than presently available.     

Spin physics at e<Superscript>+</Superscript>e<Superscript>−</Superscript> colliders

A large number of measurement related to spin was performed during the last decade at the e ⁺ e ^? colliders LEP and SLC providing important information on the dynamics of high energy interactions. In this paper three main topics will be covered: the measurements of the electroweak couplings, the study of fragmentation dynamics and the search for physics beyond the Standard Model.     

Accurate characterisation of the C(3)<Superscript>1</Superscript>Σ<Superscript>+</Superscript> state of the NaRb molecule

We present a first detailed experimental study of the C(3)¹Σ⁺ state of the NaRb molecule converging to the Na(3p) + Rb(5s) states of separated atoms. Two different high resolution spectroscopic methods have been applied: the Fourier transform spectroscopy of laser induced fluorescence and the V-type optical-optical double resonance polarization labeling spectroscopy. The entire data field for the C¹Σ⁺ state of Na⁸⁵Rb and Na⁸⁷Rb consists of rovibrational levels with v'=0–64 and J'=4–123. The data were incorporated into a direct fit of a single potential energy curve to the level energies using the Inverted Perturbation Approach method. As the experimental data extend to the “shelf" region of the potential at large internuclear separations of 8.5 ?, the C state's suitability for photoassociation yielding cold heteronuclear NaRb is discussed. Electronic supplementary material Online Material     

Laser control of the low-temperature <Emphasis Type="Italic">e</Emphasis><Superscript>−</Superscript>+O<Stack><Subscript>2</Subscript><Superscript>+</Superscript></Stack> reaction

The dissociative recombination theory of slow electrons with molecular ions in a strong monochromatic light field is developed. Classifications of all possible transitions and reaction mechanisms are presented. The potential energy curves of the oxygen molecule O₂^** dissociative states and partial cross sections are calculated.     

Gamow-Teller 1<Superscript>+</Superscript> states in <Superscript>112–124</Superscript>Sb isotopes

The violated supersymmetry property of the pairing interaction between nucleons were restored using the Pyatov method [Pyatov and Salamov, Nucleonica 22, 127 (1977)]. The eigenvalues and eigenfunctions of the restored Hamiltonian with the separable residual Gamow-Teller effective interactions in the particle-hole and particle-particle channels were solved within the framework of proton-neutron quasirandom phase approximation (pnQRPA). The Gamow-Teller resonance energies for ^112–124Sb isotopes and the differential cross-sections for Sn(³He, t)Sb reactions at E(³He) = 200 MeV occurring by the excitation of the Gamow-Teller resonance state were calculated. The calculated values were compared with other calculations and the corresponding experimental data.     

Stereodynamics of the reaction He+H<Stack><Subscript>2</Subscript><Superscript>+</Superscript></Stack> → HeH<Superscript>+</Superscript> + H: a theoretical study

Quasiclassical trajectory method for the title reaction He +H₂⁺ → HeH⁺ + H was carried out on the potential energy surface which was revised by Aquilanti et al. [Chem. Phys. Lett. 469, 26 (2009)]. The initial vibrational quantum number of reactant was set as v=1, v=2 and v=3. Stereodynamics information of the reaction was obtained, such as the distributions of product angular momentum P(θ _r ), P(ϕ _r ),p(ϕ _r , θ _r ) and the two commonly used polarization-dependent differential cross sections (PDDCSs) (2π/σ)(dσ ₀₀/dω _t ) and (2π/σ)(dσ ₂₀/dω _t ), to get the alignment and orientation of product molecules. The results show that the influence of both the collision energy and vibrational quantum number (v) to the reaction are highly sensitive.     

Two-neutrino double- β decay of 94 ⩽ A ⩽ 110 nuclei for the 0<Superscript>+</Superscript> → 0<Superscript>+</Superscript> transition

The two-neutrino double-beta decay of ^{94, 96}Zr,^98,100Mo,¹⁰⁴Ru and ¹¹⁰Pd nuclei for the 0⁺0⁺ transition is studied in the PHFB model in conjunction with the summation method. In the first step, the reliability of the intrinsic wave functions has been established by obtaining an overall agreement between a number of theoretically calculated spectroscopic properties and the available experimental data for ^{94, 96}Zr,^94,96,98,100Mo, ^98,100,104Ru, ^104,110Pd and ¹¹⁰Cd isotopes. Subsequently, the PHFB wave functions of the above-mentioned nuclei are employed to calculate the nuclear transition matrix elements M₂ as well as half-lives T_1/2². Furthermore, we have studied the effects of deformation on the M₂.     

Potential energy of <Superscript>∞</Superscript>H<Stack><Subscript>2</Subscript><Superscript>-</Superscript></Stack>(<Superscript>2</Superscript>∑<Stack><Subscript>u</Subscript><Superscript>+</Superscript></Stack> in the bound-state region

An accurate calculation of the lowest negative electronic state of H ₂ ^- (fixed nuclei) is reported using the CCSD(T) method and doubly augmented cc-pv5z basis set. Comparison has been made with the reference data by Senekowitsch et al. [Chem. Phys. Lett. 111 (1984) 211]. Owing to larger size of the basisset and inclusion of triple excitations, no vertical shift in this work is necessary to reproduce the asymptotics of H + H ^-. In addition, the effect of basis-set truncation is estimated, based on the complete-basis-set extrapolation method. The contribution of correlated electron-proton motion to the electron-energy curve for H₂ ^– dynamics is pointed out.Dedicated to Prof. Jií Horáek on the occasion of his 60th birthday.     

Processes e<Superscript>+</Superscript>e<Superscript>−</Superscript> → π<Superscript>0</Superscript>(π<Superscript>0</Superscript>′) γ in extended NJL model

The processes of electron-positron annihilation into π⁰γ and into π′(1300)γ are considered within an extended NJL model. The intermediate vector mesons ρ ⁰, ω ρ′(1450), and ω(1420) are taken into account. The latter two mesons are treated as the first radial excited states. They are incorporated into the NJL model by means of a polynomial form factor. Numerical predictions for the cross-sections of these processes are received for the center-of-mass energies below 2 GeV. Our results for the π⁰γ production are in agreement with experimental data obtained in the energy region 600–1020 MeV.     

Photoproduction of π<Superscript>0</Superscript>π<Superscript>+</Superscript> pairs on proton and deuteron

The reaction of π⁰π⁺ photoproduction on free and quasi-free protons with γ-ray energies from 0.5 to 1.5 GeV has been studied. Its cross section was measured in the range θ _π ⁰ ≥ 20°. The distributions of π⁰π⁺, π⁰n, and π⁺n invariant masses were analyzed. The experiment was performed using the Compton back-scattered γ-ray beam at the GRAAL facility (Grenoble, France), applying liquid deuterium and hydrogen targets and a large-aperture (almost 4π) detector. Particular attention was paid to analysis of systematic errors related to the neutron detection efficiency.     

On the <Emphasis Type="Italic">K</Emphasis><Superscript><Emphasis Type="Italic">π</Emphasis></Superscript> = 0<Superscript>+</Superscript> rotational bands in the <Superscript>178</Superscript>Hf nucleus

The results obtained by studying the angular distributions of gamma rays with respect to the neutron-beam axis in the reaction ¹⁷⁸Hf(n, n′γ) involving the deexcitation of the K ^π = 0⁺ rotational bands of ¹⁷⁸Hf are presented.New information about themultipole-mixing parameter δ in gamma transitions from the levels of these bands is obtained. The K ^π = 0₄⁺ band is constructed anew. The relationship between the parameter δ for the (2⁺0 _n −2⁺0₁) gamma transition and the energy gap Δ _n = E _lev(2⁺0 _n ) − E _lev(0⁺0 _n ), on one hand, and the quasiparticle structure of the rotational band, on the other hand, is discussed for ¹⁷⁸Hf on the basis of the quasiparticle-phonon model.     

A study of the dynamical-fluctuation property inside jets in e<Superscript>+</Superscript>e<Superscript>−</Superscript> collisions

A study of the dynamical-fluctuation property of 2-jet events is carried out. It is found that the dynamical fluctuations of the hadronic system inside 2-jet events change with the variation of the cut parameter Y_cut. There is a transition point, where the dynamical fluctuations in these systems are circular in the transverse plane; and are elliptical in the longitudinal-transverse planes. It is shown that this transition point corresponds to the scale of visible jets. Meanwhile, the dynamical fluctuation properties inside a single-jet in 2-jet and 3-jet events are compared. The dynamical fluctuations inside quark- and gluon-jets are found to be qualitatively different. A scale for the “visible gluon jet” production is thus obtained.     

Statistical hadronization with exclusive channels in e<Superscript>+</Superscript>e<Superscript>−</Superscript> annihilation

We perform a systematic analysis of exclusive hadronic channels in e⁺e⁻ collisions at center-of-mass energies between 2.1 and 2.6 GeV within the statistical hadronization model. Because of the low multiplicities involved, calculations have been carried out in the full microcanonical ensemble, including conservation of energy-momentum, angular momentum, parity, isospin, and all relevant charges. We show that the data are in an overall good agreement with the model for an energy density of about 0.5 GeV/fm³ and an extra-strangeness suppression parameter γ _S ∼0.7, essentially the same values found with fits to inclusive multiplicities at higher energy.     

An analytical model of P <Superscript>+</Superscript>InAsSbP/n <Superscript>0</Superscript>-InAs/n <Superscript>+</Superscript>-InAs single heterojunction photodetector for 2.4–3.5 μm region

In this paper, a surface illuminated InAsSbP/InAs photodetector has been analyzed for operation in 2.0–3.5 m wavelength region. The influence of different dark current components on the resistance-area product (RA) of the photodetector has been estimated theoretically. The results obtained on the basis of the model are found to be in good agreement with the experimental data reported by others. The high value of detectivity of the device at room temperature will make it attractive for use in optical gas sensor.     

Cold and ultracold collisions of MgH (<Superscript>2</Superscript>Σ<Superscript>+</Superscript>) with helium

The cross sections for rotational, fine-structure and projection-change transitions in collision of MgH (²Σ⁺) molecule with ³He and ⁴He atoms were computed at cold and ultracold temperatures using the ab initio potential energy surface. The significant suppression feature and resonance pattern caused by spin-rotation interaction were found and discussed. The collisions exhibit a strong isotope effect in the ultracold regime. The rotational relaxations of the fine-structure excited energy levels tendentiously preserve the F index. The ratio of the cross sections for elastic and spin-flipping collision with ³He partner is always greater than seven orders of magnitude for the energy range 10^-6−1cm^-1 and suggests the MgH molecule is a good candidate for ³He buffer gas cooling.