Scalar interaction limits from the beta-nu correlation of trapped radioactive atoms

We have set limits on contributions of scalar interactions to nuclear beta decay. A magneto-optical trap provides a localized source of atoms suspended in space, so the low-energy recoiling nuclei can freely escape and be detected in coincidence with the beta. This allows reconstruction of the neutrino momentum, and the measurement of the beta-nu correlation, in a more direct fashion than previously possible. The beta-nu correlation parameter of the 0(+)-->0(+) pure Fermi decay of (38)K(m) is a =0.9981+/-0.0030+0.0032 / -0.0037, consistent with the standard model prediction a =1.     

Recoil momentum spectroscopy of highly charged ion collisions on magneto-optically trapped Na

We have used a cold ( T<1 mK), laser-cooled target of Na atoms confined in a magneto-optical trap to study electron capture processes during highly charged ion-sodium atom collisions at keV energies. Momentum distributions of target ions were determined by employing time-of-flight and position sensitive detection of the Na ions, produced during the collisions and extracted by a weak electric field. In this way impact parameter sensitive information about multielectron capture processes is obtained.     

Structure of the mirror nuclei21Ne and21Na

Theγ-decay of levels in²¹Ne up to 10 MeV excitation energy has been investigated byn — γ coincidence measurements initiated with the¹⁸O(α, nγ) reaction at 12, 13, 14.5 and 15.4 MeV bombarding energies. Spin(-parity) assignments of excited states are obtained by combining then — γ angular correlation measurements performed atE _α=11, 11.82 and 13.6 MeV with a consideration of lifetimes, neutron penetrabilities of the unbound states, and information from the mirror nucleus²¹Na. The resulting values of E_x[keV]?J ^π are as follows: 4525-5⁺, 4686-3⁺, 5431-7⁺, 5549-3⁺, 5819-7^?, 6175-7⁺, 6268-9⁺, 6550-9, 6639-9, 7006-7⁺, 7041-9, 7356-7 or 9, 7422-11^(?), 7648-7⁺, 7981-11 or (7⁺), 8154-9, 8240-11, 8664-9^? or 11 or 13^?, 9401-13^?, 9867-13^? or 15⁺, 9941-13^? or 15 or 17⁺. The assignment of mirror levels in²¹Ne —²¹Na has been extended to the 6175 keV level of²¹Ne. Excitation energies, electromagnetic properties, Gamow?Teller matrix elements and spectroscopic factors of positive parity states are compared with the results of shell-model calculations which employ a unifieds—d shell Hamiltonian and the unrestricted configuration space of the 0d _5/2 —1s _1/2—0d_3/2 shell. Collective properties contained in shell model wave functions are explored up to the termination of bands atJ=17/2 or 19/2. The spectrum of intruder states in²¹Ne is observed to begin with a 5628 keV,J ^π=7/2⁺ state. The 7422, 8664 and 9401 keV levels are assigned as members of previously established negative-parity rotational bands.     

Beta-alpha correlation in the decay of 20Na

We have measured the β-α angular correlation in the allowed positron decay of ²⁰Na to the 7.42 MeV state of ²⁰Ne. The correlation is of the form $\text{1 +}\text{a}\text{cos}\text{θ +}\text{p}\text{cos}{}^2\text{θ}$. We find $\text{p}\text{= ?0.003 ± 0.005}$ in reasonable agreement with expectations based on the conserved vector current theory.     

Photoabsorption resonances of Na20, Na21Cl and Na22Cl2 clusters

Plasma resonance profiles in the visible part of the spectrum were measured by photoabsorption spectroscopy for the clusters Na₂₀, Na₂₁Cl and Na₂₂Cl₂ in a beam. The resonance positions in Na₂₀ and Na₂₁Cl are close, suggesting that the Cl^- ion does not locate at the center of the metallic droplet and does not strongly modify the effective valence electron density. The spectrum of Na₂₂Cl₂ is noticeably dissimilar to the other two, raising the possibility of structural differences and/or incomplete charge transfer.     

Measurement of spin correlation in tt production using a matrix element approach

We determine the fraction of tt events with spin correlation, assuming that the spin of the top quark is either correlated with the spin of the top antiquark as predicted by the standard model or is uncorrelated. For the first time we use a matrix-element-based approach to study tt spin correlation. We use tt → W+ b W- b → ?+ νb?- ν b final states produced in pp collisions at a center-of-mass energy sqrt(s)=1.96 TeV, where ? denotes an electron or a muon. The data correspond to an integrated luminosity of 5.4 fb(-1) and were collected with the D0 detector at the Fermilab Tevatron collider. The result agrees with the standard model prediction. We exclude the hypothesis that the spins of the tt are uncorrelated at the 97.7% C.L.     

Bloch oscillations of quasispin polaritons in a magneto-optically controlled atomic ensemble

We consider the propagation of quantized polarized light in a magneto-optically-manipulated atomic ensemble with a tripod configuration. A polariton formalism is applied when the medium is subjected to a washboard magnetic field under electromagnetically-induced transparency. The dark-state polariton with multiple components is achieved. We analyze the quantum dynamics of the dark-state polariton using experimental data from the rubidium D1-line. It is found that one component propagates freely, however the wave packet trajectory of the other component performs Bloch oscillations.     

Ground-state correlation properties of charged bosons trapped in strongly anisotropic harmonic potentials

We study systems of a few charged bosons contained within a strongly anisotropic harmonic trap. A detailed examination of the ground-state correlation properties of two-, three-, and four-particle systems is carried out within the framework of the single-mode approximation of the transverse components. The linear correlation entropy of the quasi-1D systems is discussed in dependence on the confinement anisotropy and compared with a strictly 1D limit. Only at weak interaction the correlation properties depend strongly on the anisotropy parameter.     

Ground-state correlation properties of charged bosons trapped in strongly anisotropic harmonic potentials

The core width and Peierls barrier and stress for Shockley partials in InP have been investigated using the improved P-N theory. The core width of 90° partial is about 1.6 times wider than that of 30° partial, and both of them are very narrow: core width ξ < 0.5b. In calculating the Peierls barrier and stress, the contribution from stain energy ignored by classical P-N theory has been considered. The calculated results show that when the dislocation moves, both the misfit and strain energies change periodically. They cancel each other due to the same order but opposite phases. Accordingly, the Peierls barrier and stress calculated from improved P-N theory are much lower than those calculated from the classical P-N theory. The Peierls barrier for 90° and 30° partials obtained by us is respectively about  ~0.047 eV/Å and 0.044–0.075 eV/Å, the Peierls stress is respectively about 3.7–5.0 GPa and 4.2–6.9 GPa.     

Short-distance correlation properties of the Lieb-Liniger system and momentum distributions of trapped one-dimensional atomic gases

We derive exact closed-form expressions for the first few terms of the short-distance Taylor expansion of the one-body correlation function of the Lieb-Liniger gas. As an intermediate result, we obtain the high-p asymptotics of the momentum distribution of both free and harmonically trapped atoms and show that it obeys a universal 1/p(4) law for all values of the interaction strength. We discuss the ways to observe the predicted momentum distributions experimentally, regarding them as a sensitive identifier for the Tonks-Girardeau regime of strong correlations.     

Measurement of the 24Mg(p, t)22Mg reaction for the states near the 21Na + p threshold

Differential cross-sections of the ²⁴Mg(p, t)²²Mg reaction were measured at 34.68 MeV for the states near the proton threshold at 5.502 MeV in ²²Mg. Among them, the new states at 5.962, 6.046, 6.246 and 6.323 MeV, which were reported previously, have been confirmed. Angular distributions for these states were analyzed by distorted-wave Born-approximation calculations to deduce the spins and parities. The angular distribution for the 5.714 MeV state, which is considered to be most crucial for the stellar reaction ²¹Na(p, γ)²²Mg, has been found to be consistent with J ^π = 2⁺ assignment. The 6.046 MeV state is newly assigned to have J ^π = 0⁺, and the 5.962 MeV state is tentatively assigned to have J ^π = (1^-). These two states will also play an important role for ²²Mg production in novae. Received: 7 March 2002 / Accepted: 7 May 2002     

Coulomb excitation of radioactive 20, 21Na

The low-energy structures of the radioactive nuclei ^{20, 21}Na have been examined using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. Beams of ～ 5×10⁶ ions/s were accelerated to 1.7MeV/A and Coulomb excited in a 0.5mg/cm^2 ^natTi target. Two TIGRESS HPGe clover detectors perpendicular to the beam axis were used for $ \gamma$ -ray detection, while scattered nuclei were observed by the Si detector BAMBINO. For ²¹Na , Coulomb excitation from the 3/2⁺ ground state to the first excited 5/2⁺ state was observed, while for ²⁰Na , Coulomb excitation was observed from the 2⁺ ground state to the first excited 3⁺ and 4⁺ states. For both beams, B ( $ \lambda$ L) values were determined using the 2⁺ $ \rightarrow$ 0⁺ de-excitation in ⁴⁸Ti as a reference. The resulting B(E2) ↓ value for ²¹Na is 137±9 e^2fm^4, while the resulting B( $ \lambda$ L) ↓ values for ²⁰Na are 55±6 e^2fm^4 for the 3⁺ $ \rightarrow$ 2⁺ , 35.7±5.7 e^2 fm^4 for the 4⁺ $ \rightarrow$ 2⁺ , and 0.154±0.030 μ_N^2 for the 4⁺ $ \rightarrow$ 3⁺ transitions. This analysis significantly improves the measurement of the ²¹Na B(E2) value, and provides the first experimental determination of B( $ \lambda$ L) values for the proton dripline nucleus ²⁰Na .-1     

Measurement of the angular correlation of positron annihilation radiation using a Ge(Li) detector

The use of a Ge(Li) detector as one of the radiation detectors in a long slit angular correlation measurement of the annihilation radiation is described. The measurement yields information similar to that obtained by point slit or spark chamber geometry. The results for a copper single crystal are reported.     

Cluster states prepared by using hot trapped ions

We propose a scheme for the preparation of one-dimensional and two-dimensional cluster states by using hot trapped ions. The scheme is based on the interaction between two ions and bichromatic radiation. The vibrational mode in our protocol is only virtually excited so that the system is insensitive to the thermal field. In addition, we only use two levels of ions as qubits and the successful probability may achieve 100%.     

Fast thermometry for trapped atoms using recoil-induced resonance

We have employed recoil-induced resonance(RIR) with linewidth on the order of 10 k Hz to demonstrate the fast thermometry for ultracold atoms. We theoretically calculate the absorption spectrum of RIR which agrees well with the experimental results. The temperature of the ultracold sample derived from the RIR spectrum is T = 84 ± 4.5 μK, which is close to 85 μK that measured by the method of time-of-flight absorption imaging. To exhibit the fast measurement advantage in applying RIR to the ultracold atom thermometry, we study the dependence of ultracold sample temperature on the trapping beam frequency detuning. This method can be applied to determine the translational temperature of molecules in photoassociation dynamics.     

DSA lifetimes in21Na and23Na derived from experimental stopping parameters

The lifetimes for the second excited state in²¹Na and for the second to ninth excited states in²³Na have been determined with the DSA method using Ta₂O₅ and Ta as stopping materials. In the DSA analysis the experimental stopping parameters determined in the present and earlier works were utilized. The reanalysis of some earlier studies has brought very good consistency to the scattered results. Comparison of the observed transition strengths with theory has also been made.     

Measurement of the decoherence of a mesoscopic superposition of motional states of a trapped ion

We propose a scheme to observe the decoherence of a mesoscopic superposition of two coherent states in the motion of a trapped ion. In the scheme the ion is excited by two perpendicular lasers tuned to the ion transition. The decoherence is revealed by the decrease of the correlation between two successive measurements of the internal state of the ion after relevant laser－ion interaction.