The LPCTrap experiment: measurement of the ��-��?angular?correlation in 6He+ decay using a transparent Paul trap

The LPCTrap experiment is devoted to the precise measurement of the ??-?? angular correlation parameter, a _?|? , in the pure Gamow-Teller decay of ⁶He⁺. This experiment is motivated by the search of the presence of tensor type contributions in the weak interaction. The radioactive source is confined in a transparent Paul trap installed at LIRAT, the low energy beam line of the SPIRAL facility. The ??-?? correlation is studied by measuring the time of flight of the recoil ions detected in coincidence with the ?? particles. During the last experiment, a total of 4 × 10⁶ coincidence events have been recorded which would enable to determine the coefficient with a statistical uncertainty of 0.5%. The status of the analysis is presented in this contribution.     

Determination of the geometric parameters κz and κr of a linear Paul trap

An effective method for determining the geometric parameters of a linear Paul trap is provided and carried out in this paper. The method is based on exciting the secular motion of laser-cooled Ca⁺ ions in a linear Paul trap with varied trapping potentials. Taking advantage of the segmented structure of the linear Paul trap, both the axial and the radial geometric parameters are obtained by applying external excitation fields to the trapping electrodes directly. The axial geometric parameter of our linear Paul trap is determined to be 0.374(3), and, for the first time, the radial geometric parameter is determined to be 0.928(2).     

Controlled synthesis and analysis of He–H+3 in a 3.7 K ion trap

Complexes of the triatomic hydrogen ion with helium were synthesised in a low-temperature 22-pole rf ion trap at He number densities of up to 10¹⁶ cm^?3. Absolute ternary rate coefficients for sequentially attaching He atoms have been determined from the growth of complexes with increasing storage time. The number of helium-tagged ions is significantly reduced when increasing the nominal temperature from 4 to 25 K. Competition between attachment and dissociation via collisions leads to stationary He_n–H⁺₃ (n up to 9) distributions. State-specific excitation of the trapped H⁺₃ ions via IR transitions significantly reduces the formation of complexes. Tuning the laser to Δv₂ = 1 transitions in the range of 2726 cm^?1 leads to LIICG lines, i.e., to spectra caused by laser-induced inhibition of complex growth. In addition, almost 100 lines have been found between 2700 and 2765 cm^?1, which are attributed to laser-induced dissociation of the in situ formed He–H⁺₃ complex ions. These lines are not yet assigned; however, their absorption strength, statistics and predissociation lifetimes provide interesting information on both the stable complexes as well as on scattering resonances in low-energy H⁺₃+He collisions. New calculations of the potential energy surface will help to analyse the dissociation spectrum. There are some indications that para-H⁺₃ is enriched under the conditions of the present experiment.     

Study of the SF 6 − ion lifetime in a rf quadrupole trap

We use an experimental apparatus to study SF ₆ ^– ions lifetimes. These ions are created inside a quadrupole rf trap by charge exchange between highly excited argon atoms and SF₆ molecules. Ions are observed from 200 s up to 15 ms after their creation time. In order to explain experimental results, collisions with SF₆ molecules and the influence of ionized core of argon are taken into account. A part of SF ₆ ^– ions are stabilized by the last influence. These results evidence a radiative stabilization phenomenon, the lifetime of which is estimated at about 5 ms.Equipe de Recherche associée au C.N.R.S. 0898Laboratoire associé au C.N.R.S. 0282     

Temperature Non-Uniformity Along the Active Element of a He–Ne Laser

Russian Physics Journal - Temperature distribution along the discharge of a He–Ne laser is studied, its non-uniformity is detected, and possibility of its regulation is analyzed.     

Spatial structure of a Bose–Einstein condensate in a combined trap

We study the spatial structure of a Bose–Einstein condensate(BEC) with a space-dependent s-wave scattering length in a combined trap. There exists a space-dependent nonlinear atomic current in the system. The atomic current has an important influence on the spatial structure of the BEC. Research findings reveal that a large chemical potential can effectively suppress the chaotic spatial structure in the BEC system. Due to the large chemical potential, a strong atomic current is necessary to make...     

Temperature dependence of structure and density for D?O confined in MCM-41-S

Using neutron diffraction, we have tracked the temperature dependence of structural properties for heavy water confined in the nanoporous silica matrix MCM-41-S. By observing the correlation peak corresponding to the pore-pore distance, which is determined by the scattering contrast between the silica and the water, we monitored the density of the confined water. Concurrently, we studied the prominent first diffraction peak of D(2)O at ≈ 1.8 ?(-1), which furnishes information on the microscopic arrangement of the water molecules. The data show the presence of a density maximum at ≈ 275 K (± 10 K), a property similar to bulk water, and the occurrence of a density minimum at ≈ 180 K (± 10 K). The prominent diffraction peak of D(2)O is found to shift and sharpen over a wide T range from 200 to 270 K, reflecting structural changes that are strongly correlated with the changes in density. We also observe the continuous formation of external ice, arising from water expelled from the pores while expansion takes place within the pores. An efficient method for monitoring the density of the confined D(2)O using a triple-axis spectrometer is demonstrated.     

SU(3) spin–orbit-coupled Bose–Einstein condensate confined in a harmonic plus quartic trap

We consider a SU(3) spin–orbit coupled Bose–Einstein condensate confined in a harmonic plus quartic trap.The ground-state wave functions of such a system are obtained by minimizing the Gross–Pitaevskii energy functional, and the effects of the spin-dependent interaction and spin–orbit coupling are investigated in detail.For the case of ferromagnetic spin interaction, the SU(3) spin–orbit coupling induces a threefold-degenerate plane wave ground state with nontrivial spin texture.For the case of antiferromagnetic spin interaction, the system shows phase separation for weak SU(3) spin–orbit coupling, where three discrete minima with unequal weights in momentum space are selected, while hexagonal honeycomb lattice structure for strong SU(3) SOC, where three discrete minima with equal weights are selected.     

Control Method of Cooling a Charged Particle Pair in a Paul Trap

We propose a simple feedback cooling method, including both the component feedback and the velocity feedback,for cooling a charged particle pair in a Paul trap. It is found that the system can be cooled to periodic orbits;and if control intensity is strong, the system can be cooled to a one-periodic orbit, which is only in a horizontalplane. The result shows that the cooled system is also robust for noise.     

Bose–Einstei condensation of dipolar excitons in a ring trap

The temperature of Bose–Einstein condensation and the fraction of particles in a condensate for a system of spatially indirect dipole excitons in an electrostatic ring trap have been found. If only levels of the radial motion close to the bottom of the potential well of the trap are populated considerably, the oscillatory model of the single-particle spectrum is applicable. In this case, even the strong exciton–exciton interaction can be taken into account.     

Coulomb predissociation rates of He dµ molecular ions

The predissociation or particle emitting decay rates of muonic molecular ions³He dµ and⁴He dµ are estimated by means of the complex rotation method. We use a highly accurate variational three-bodyP-wave function based on random-tempered Slater-type exponential expansion. A resonance eigenvalue ofE=–48.420 89 eV and =0.348 × 10^–3 eV for the³He dµ ion and a resonance eigenvalue ofE=–58.225 303 eV and =0.118 × 10^–3 eV for the⁴He dµ ion have been obtained. These results are in a good agreement with the ones previously obtained by Kino and Kamimura by scattering calculation with the non-adiabatic coupled-rearrangement-channel method.     

Temperature measurement of axisymmetric partially premixed methane/air flame in a co-annular burner using Mach–Zehnder interferometry

In this paper partially premixed laminar methane/air co-flow flame is studied experimentally. Methane–air flame is established on an axisymmetric co-annular burner. The fuel-air jet flows from the central tube while the secondary air flows from the region between the inner and the outer tube. The aim is to investigate the flame characteristics for methane/air axisymmetric partially premixed flame using Mach–Zehnder interferometry. Different equivalence ratios (φ=1.4–2.2) and Reynolds numbers (Re=100–1200) are considered in the study. Flame generic visible appearance and the corresponding fringe map structures are also investigated. It is seen that the fringe maps are poorly influenced by equivalence ratio variations at constant Reynolds number but are significantly affected by Reynolds number variations in constant equivalence ratio. Temperatures obtained from optical techniques are compared with those obtained from thermocouples and good agreement is observed. It is concluded that the effect of Reynolds number increment on maximum flame temperature is negligible while equivalence ratio reduction increases maximum flame temperature substantially.     

Decay processes of He H µ-molecular ions in the hyperspherical surface function method

The method of hyperspherical surface functions has been applied to the calculation of eigenvalues and eigenfunctions of muonic molecular ions^3,4Hedµ. Binding energies and decay rates for the states of the total angular momentumL=0, 1, 2 have been obtained.     

The measurement of bending wave intensity in a two-dimensional structure

I.IntroductionOfallstructuralwaves,bendingwaveismostimportant.Itiseasilyexcitedandresultsinairbornenoiseradiation'Inpractice,itisnecessarytodeterminetheenergydistributionandpowertransmissionincoupledstructl1res.Bendingwaveenergycanbecalculatedfrombendingwaveaccelerationwhilebendingwavepowertransmissionischaracterizedbybendingwaveintensitywhichisavectorgivillgthemagnitudeanddirection.TheengineeringaPplicationofthevectorpropertyofbendingwaveilltensityisnumerous[1~3]buttheinvestigationinitispre…     

Coherence-Like States of Two Coulomb-Correlated Ions Confined in a Paul Trap

We report the n x n＇ coherence-like state solutions in the cases of n, n＇ = 1, 2,... for the system including two Coulomb-correlated ions confined in a one-dimensional Paul trap with a time-dependent harmonic potential. One of the n＇ exact solutions of the centre-of-mass motion describes a generalized coherent state. For a small driving strength the n approximate solutions of relative motion are constructed, which describe the coherent oscillations of the two ions around the classical equilibrium position.     

Atomic charges of Cl− ions confined in a model Escherichia coli ClC−Cl−/H+ ion exchanger: a density functional theory study

We present extensive semi-empirical and pseudo-potential density functional theory calculations dedicated to analyse the stability, charge density distribution and migration behaviour of Cl^? ions confined in model Escherichia coli (ec) ClC?Cl^?/H⁺ ion-exchangers. Following recent high-resolution crystal structure determination in these kinds of systems, we use a finite-cluster model approach and construct various chemically simplified pore structures made of a glutamate residue ?CH₂?CH₂?COO^? (E148) and its closets 15, 19, 23 and 26 amino acids into which the Cl^? ions will be confined. We reveal the sequence of molecular rearrangements induced on the E148 chain, which blocks the middle of the conduction pathway, leading to the pore opening. The ?CH₂?CH₂?COO^? fragment shows notable variations in its average charge density for small changes in the intra-cellular environment varying from ?0.4e to ?0.3e to ?0.1e in the presence of zero, one and two confined Cl^? ions, respectively, a result that reveals an interesting functionality of the E148 chain during Cl^? conduction. We also obtain complex fluctuations in the ionic charge of the confined Cl^? ions varying from ～?0.7e to ?0.2e, which deviate significantly from the value (?1e) usually used in classical simulations. By attaching a single H species to one of the oxygens of the glutamate group, we obtain that the ?CH₂?CH₂?COOH fragment has now a small effective charge of ～+0.25e. The energy barriers opposing the exit of the Cl^? ions from our considered ion-exchangers vary from 0.65 eV to 4.7 eV, the smallest values being obtained for model structures exhibiting a high degree of flexibility and having protonated E148 fragments. Our results reinforce previous findings and provide additional physical insight, at the atomic level, on the gating process. Finally, we underline the importance of using electronically polarisable force fields to describe the transport of anionic species through this kind of molecular constrictions.     

Quantum entanglement in a two—dimensional ion trap

In this paper,we investigate the quantum entanglement in a two-dimensional ion trap system.we discuss the quantum entanglement between the ion and phonons by using reduced entropy,and that between two degrees of freedom of the vibrational motion along x and y directions by using quantum relative entropy.We discuss also the influence of initial state of the system on the quantum entanglement and the relation between two entanglements in the trapped ion system.     

Direct Measurement of 12C?+?4 He Fusion Cross Section Near Stellar energy

The reaction ¹²C?+?⁴He ?? ¹⁶O?+??? at E _cm?= 0.3?MeV plays an important role in stellar evolution, but the reaction cross section has not been measured yet. Recently we succeeded to measure total cross section of the reaction down to E _cm?= 1.5?MeV at Kyushu University. We have a plan to measure the cross section down to 0.7?MeV in several years, and to extrapolate the results to 0.3?MeV.     

Spin-spin interaction of Ni2+ ions in ZnSiF6·6H2O

The angular dependences of the electron spin resonance spectrum of 1% Ni²⁺ ions in a ZnSiF₆·6H₂O matrix are investigated experimentally at 36 GHz and 4.2 K. Besides the main spectrum of the isolated ion, we observed a spectrum due to interacting pairs of Ni²⁺ ions, located in the first (nn) and second (2n) coordination spheres and coupled by, besides the magnetic dipole-dipole interaction, isotropic exchange: J _nn = (−197±1)×10⁻⁴, J _2nα = (−5±1)×10⁻⁴, and J _2nβ = (3±2)×10⁻⁴ cm⁻¹. Lines due to other isolated Ni²⁺ ions, which have a different initial splitting D, are also present in the spectrum with intensity comparable to the pair spectrum. Low-symmetry distortions of the crystal field are observed, caused by a pair of impurity ions located close to one another. It is shown that the previously proposed interpretation is incorrect. Fiz. Tverd. Tela (St. Petersburg) 41, 1602–1608 (September 1999)