Erratum: Improving the efficiency of ultracold dipolar molecule formation by first loading onto an optical lattice [Phys. Rev. A 81, 011605 (2010)]
No abstract prepared.
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Results for “INTERMEDIATE STATE”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Antiferromagnetism in a bosonic mixture of rubidium ({sup 87}Rb) and potassium ({sup 41}K)
We simulate the experimental possibility of observing antiferromagnetic (AF) order in bosonic mixtures of rubidium ({sup 87}Rb) and potassium ({sup 41}K) in a two-dimensional optical lattice in the presence of harmonic confinement. By tuning the interspecies interactions and the lattice heights, we have found the ground states, within the mean-field approximation, that interpolate from phase separation to AF order. For a moderate lattice height, the coexistence of the Mott and AF phases is possible for the Rb atoms whereas the K atoms remain in the AF-superfluid phase. This observation may provide an experimentally feasible route to hitherto unobserved AF order for {sup 87}Rb-{sup 41}K mixtures.
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Vibrational stabilization of ultracold KRb molecules: A comparative study
The transfer of weakly bound KRb molecules from levels just below the dissociation threshold into the vibrational ground state with shaped laser pulses is studied. Optimal control theory is employed to calculate the pulses. The complexity of modeling the molecular structure is successively increased in order to study the effects of the long-range behavior of the excited-state potential, resonant spin-orbit coupling, and singlet-triplet mixing.
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Bose-Einstein condensation in the presence of artificial spin-orbit interaction
Bose-Einstein condensation in the presence of a synthetic spin-orbit interaction is considered, focusing on the case where a Dirac or Rashba potential is generated via a tripod scheme. We found that the ground states can be either plane-wave states or superpositions of them, each characterized by their unique density distributions.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Narrowband-biphoton generation due to long-lived coherent population oscillations
We study the generation of paired photons due to the effect of four-wave mixing in an ensemble of pumped two-level systems that decay via an intermediate metastable state. The slow population relaxation of the metastable state creates long-lived coherent population oscillations, leading to a narrowband nonlinear response of the medium which determines the narrow spectral width and long coherence time of the biphotons.
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High-brightness switchable multiwavelength remote laser in air
We demonstrate a harmonic-seeded switchable multiwavelength laser in air driven by intense midinfrared femtosecond laser pulses, in which population inversion occurs at an ultrafast time scale (i.e., less than {approx}200 fs) owing to direct formation of excited molecular nitrogen ions by strong-field ionization of inner-valence electrons. The bright multiwavelength laser in air opens the perspective for remote detection of multiple pollutants based on nonlinear optical spectroscopy.
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Effects of molecular rotation after ionization and prior to fragmentation on observed recoil-frame photoelectron angular distributions in the dissociative photoionization of nonlinear molecules
Experimental angle-resolved photoelectron-photoion coincidence experiments measure photoelectron angular distributions (PADs) in dissociative photoionization (DPI) in the reference frame provided by the momenta of the emitted heavy fragments. By extension of the nomenclature used with DPI of diatomic molecules, we refer to such a PAD as a recoil-frame PAD (RFPAD). When the dissociation is fast compared to molecular rotational and bending motions, the emission directions of the heavy fragments can be used to determine the orientation of the bonds that are broken in the DPI at the time of the ionization, which is known as the axial-recoil approximation (ARA). When the ARA is valid, the RFPADs correspond to molecular-frame photoelectron angular distributions (MFPADs) when the momenta of a sufficient number of the heavy fragments are determined. When only two fragments are formed, the experiment cannot measure the orientation of the fragments about the recoil axes so that the resulting measured PAD is an azimuthally averaged RFPAD (AA-RFPAD). In this paper we consider how the breakdown of the ARA due to rotation will modify the observed RFPADs for DPI processes in nonlinear molecules for ionization by light of arbitrary polarization. This model is applied to the core C $1s$ DPI of ${\mathrm{CH}}_{4}$, with the results compared to experimental measurements and previous theoretical calculations done within the ARA. The published results indicate that there is a breakdown in the ARA for two-fragment events where the heavy-fragment kinetic energy release was less than 9 eV. Finally, including the breakdown of the ARA due to rotation in our calculations gives very good agreement with the experimental AA-RFPAD, leading to an estimate of upper bounds on the predissociative lifetimes as a function of the kinetic energy release of the intermediate ion states formed in the DPI process.
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Anomalous electrical transport behavior in the vicinity of the first-order magnetostructural transition in the giant magnetocaloric Gd 4 ScGe 4
Here, magnetic, specific heat, and electrical transport measurements of Gd 4 ScGe 4 single crystals reveal sharp, discontinuous, nearly anhysteretic first-order magnetostructural transformation at $T_C$ = 63 K. The electrical resistivity exhibits two distinct regions where it increases with decreasing temperature: between $T_C$ and 120 K, as well as below 3 K; electronic transport remains conventionally metallic at all other measured temperatures, up to 325 K. The dispersion of charge carriers due to electron-paramagnon scattering is the likely reason for the observed anomalous transport above $T_C$. Additionally, the existence of intermediate lattice states near the transition recognized by the spike in the interslab Ge-Ge distances is expected to reduce the mean free path of the electrons contributing to the unusual behavior of the electrical resistivity between $T_C$ and 120 K. Beyond conventional electronic and lattice terms, the third component of likely magnetic origin contributes to the low-temperature heat capacity; the presence of spin waves may be responsible for the increased electron-magnon scattering below 3 K. Minor magnetocrystalline anisotropy is observed with the b axis as the easy magnetization axis in Gd 4 ScGe 4 . A negative deviation from linearity in the temperature dependence of the inverse magnetic susceptibility is detected below 150 K.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Excitonic Aharonov-Bohm effect in isotopically pure {sup 70}Ge/Si self-assembled type-II quantum dots
We report on a magnetophotoluminescence study of isotopically pure {sup 70}Ge/Si self-assembled type-II quantum dots. Oscillatory behaviors attributed to the Aharonov-Bohm effect are simultaneously observed for the emission energy and intensity of excitons subject to an increasing magnetic field. When the magnetic flux penetrates through the ringlike trajectory of an electron moving around each quantum dot, the ground state of an exciton experiences a change in its angular momentum. Our results provide the experimental evidence for the phase coherence of localized electron wave functions in group-IV Ge/Si self-assembled quantum structures.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Time-resolved stroboscopic neutron scattering of vortex lattice dynamics in superconducting niobium
Superconducting vortex lattices, glasses, and liquids attract great interest as model systems of crystallization and as a source of microscopic information of the nature of superconductivity. We report direct microscopic measurements of the vortex lattice tilt modulus c{sub 44} in ultrapure niobium using time-resolved small-angle neutron scattering. Aside from a general trend to faster vortex lattice dynamics for increasing temperatures, we observe a dramatic changeover of the relaxation process associated with the nontrivial vortex lattice morphology in the intermediate mixed state. This changeover is attributed to a Landau branching of the Shubnikov domains at the surface of the sample. Our study represents a showcase for how to access directly vortex lattice melting and the formation of vortex matter states for other systems.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
First spectral measurement of deuterium-tritium fusion γ rays in inertial fusion experiments
Here, the R-matrix analysis of A = 5 nuclear systems has been partially validated by applying the technique to the 5 Li system and comparing the predicted γ-ray spectrum with historical data. R-matrix analysis of the similar 5 He system was then used to predict the γ-ray spectral shape for the deuterium-tritium (DT) reaction. The resulting spectra have been used in the analysis of DT implosions on the Omega laser where the γ-ray interaction rate was measured by a gas Cherenkov detector. Comparison of predictions to experiment confirmed the presence of both 16.75 and ≈ 13 MeV γ-ray contributions; analysis, using R-matrix spectra, yielded a ratio of γ-ray emission from a transition to the intermediate excited state to that from a transition to the ground state of (2.1 ± 0.4):1, substantiating the first spectral measurement of the DT fusion γ ray in an inertial fusion environment.
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Non-termination of yrast bands at maximum configuration spin in {sup 73}Kr
High-spin states in {sup 73}Kr were studied at the XTU tandem accelerator of the Laboratori Nazionali di Legnaro using the reaction {sup 40}Ca({sup 40}Ca,alpha2pn) at a beam energy of 185 MeV. Gamma rays were detected with the EUROBALL spectrometer. Particle detection enabled us to identify the reaction channel leading to {sup 73}Kr. The yrast bands of positive and negative parity were established up to probable spins of 61/2{sup +} and 63/2{sup -}, respectively. The energies of the two identified bands agree well with the predictions of the configuration-dependent Cranked Nilsson-Strutinsky approximation and indicate that the nucleus remains collective up to the maximum spins of the respective high-spin configurations. The positive-parity band represents one of the rare cases where band non-termination at the highest spin of the configuration could be established experimentally.
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Band structures in {sup 106}Ag and systematics of shears mechanism in the Aapprox110 mass region
High-spin states of {sup 106}Ag were populated via the fusion-evaporation reaction {sup 100}Mo ({sup 11}B,5n){sup 106}Ag at a beam energy of 60 MeV. A rich level scheme with six band structures has been established. A high-K negative-parity band has been identified and assigned to the pig{sub 9/2} x nu[h{sub 11/2}(g{sub 7/2}/d{sub 5/2}){sup 2}] configuration. The positive parity DELTAI=1 band, built on the 12{sup +} state, is discussed in terms of the magnetic rotation model. The systematic study of similar bands in the Aapprox110 mass region indicates that the magnetic rotation phenomenon has, as lower boundary, the Ag isotopes at Z=47.
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Evidence for octupole excitations in the odd-odd neutron-rich nucleus {sup 142}Cs
High-spin states in the neutron-rich nucleus {sup 142}Cs are reinvestigated from a study of the spontaneous fission of {sup 252}Cf with the Gammasphere detector array. A new level scheme is built and spin-parities are assigned to levels based on angular correlation measurements and systematics. The new structure of {sup 142}Cs is proposed to be related to octupole correlations. The electric dipole moment of {sup 142}Cs is measured and a dramatic decrease of the dipole moments with increasing neutron numbers in the Cs isotopic chain is found.
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Publisher's Note: g factor of the {sup 44}Cl ground state: Probing the reduced Z=16 and N=28 gaps [Phys. Rev. C 81, 034308 (2010)]
No abstract prepared.
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Band structure and shape coexistence in {sub 56}{sup 135}Ba{sub 79}
Excited states of {sub 56}{sup 135}Ba{sub 79} at high spins are studied using the reaction {sup 130}Te({sup 9}Be,4n){sub 56}{sup 135}Ba{sub 79} at 42.5-MeV beam energy. The earlier known level scheme is extended up to 6.4-MeV excitation energy and (37/2)(Planck constant/2pi) spin with the addition of several transitions. We have performed polarization asymmetry measurements for some of the strong transitions by using a Clover detector to assign the parity. A comparison of experimental data with the results of tilted axis cranking calculations based on various configurations indicates the coexistence of multiple minima in the triaxial deformation (gamma), whereas axial symmetric deformation (epsilon{sub 2}) remains constant around 0.09.
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Noncollective aligned and antialigned states in {sup 125}I
High-spin states in {sup 125}I were populated using the reaction {sup 82}Se({sup 48}Ca,p4n) at a beam energy of 200 MeV and {gamma}-ray coincidence events were acquired with the Gammasphere spectrometer. The level scheme of {sup 125}I was extended considerably. In particular, maximally aligned states involving all eleven particles outside the {sup 114}Sn core were observed. Comparison with cranked Nilsson-Strutinsky calculations suggests that three of these states are the final I{sub max} states in terminating bands with all spin vectors aligned along a common axis. In two of these, one spin vector is antialigned and points in the opposite direction. In one of the states two spin vectors are antialigned. This is the first observation of a state with such a structure.
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High spin states in {sup 151,153}Pr, {sup 157}Sm, and {sup 93}Kr
High spin states are observed for the first time in the neutron-rich nuclei {sup 151,153}Pr, {sup 157}Sm, and {sup 93}Kr from the spontaneous fission of {sup 252}Cf. Twenty new transitions in {sup 151}Pr, twelve in {sup 153}Pr, five in {sup 157}Sm, and four in {sup 93}Kr were identified by using x-ray(Pr/Sm)-{gamma}-{gamma} and {gamma}-{gamma}-{gamma} triple coincidences. From the measured total internal conversion coefficients {alpha}{sub T} of four low-energy transitions in {sup 151,153}Pr, we determine that two bands in each nucleus have opposite parity. The interlacing E1 transitions between the bands suggest a form of parity doubling in {sup 151,153}Pr. New bands in {sup 157}Sm and {sup 93}Kr are reported. The half-life of the 354.8 keV state in {sup 93}Kr is measured to be 10(2) ns.
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