Photoassociation spectra of ultracold ~(85)Rb_2 molecule in 0_u~+ long range state near the 5S_(1/2)+ 5P_(1/2) asymptote

We investigate the high resolution photoassociation spectra of ~(85)Rb_2 molecules in 0~+_u long range state below the(5S_(1/2)+ 5P_(1/2)) asymptote. The ~(85)Rb atomic samples are trapped in a dark magneto–optical trap(MOT) and prepared in the dark state. With the help of trap loss technique, we obtain considerable photoassociation spectroscopy with rovibrational resolution, some of which have never been observed before. The observed spectrum is fitted by a rigid rotation model, and the rotational constants of ultracold ~(85)Rb_2 molecule in long range 0~+_u are obtained for different vibrational states. By applying the Le Roy–Bernstein method, we assign the vibrational quantum numbers and derive C_3 coefficient, which is used to obtain the potential energy curve.     

Superconductivity in Hole-Doped （S1-xKx）Fe2As2

A series of layered （Sr1-xKx）Fe2As2 compounds with nominal x = 0-0.40 are synthesized by solid state reaction method. Similar to other parent compounds of iron-based pnictide superconductors, pure SrFe2As2 shows a strong resistivity anomaly near 210 K, which was ascribed to the spin-density-wave instability. The anomaly temperature is much higher than those observed in LaOFeAs and BaFe2As2, the two prototype parent compounds with ZrCuSiAs- and ThCr2Si2-type structures. K-doping strongly suppresses this anomaly and induces superconductivity. Like in the case of K-doped BaFe2As2, sharp superconducting transitions at Tc ～ 38 K is observed. We perform the Hall coefficient measurement, and confirm that the dominant carriers are hole-type. The carrier density is enhanced by a factor of 3 in comparison to F-doped LaOFeAs superconductor.     

The laser-intensity dependence of the photoassociation spectrum of the ultracold Cs2（6S1/2 ＋ 6P1/2） 0＋ long-range molecular state

The high-resolution photoassociation spectrum of the ultracold cesium molecular 0＋ state below the 6S1/2 ＋ 6PI/2 limit is presented in this paper. The saturation of the photoassociation scattering probability is observed from the depen dence of the trap-loss probability on the photoassociation laser intensity. The corresponding resonant line width is also demonstrated to increase linearly with increasing photoassociation laser intensity. Our experimental data have good con sistency with the theoretical saturation model of Bohn and Julienne [Bohn J L and Julienne P S 1999 Phys. Rev. A 60 1].     

Light-induced frequency shifts for the lowest vibrational levels of ultracold Cs2 in the molecular pure long-range 0^-g state

The light-induced frequency shift(LIFS)of ultracold molecular ro-vibrational levels originates from the strong coupling of the atomic-scattering state and the bound-molecular state.In this paper,we present our experimental determination of the LIFSs of the lowest vibrational levels(v=0,1)in the purely long-range 0^-g state of ultracold cesium molecules.A high-resolution double photoassociation spectroscopy is developed,which serves as frequency ruler to measure the frequency shifts of the lowest molecular levels for Cs2.The experimental results are qualitatively consistent with the theoretical expectations.     

High resolution photoassociation spectra of an ultracold Cs2 long-range 0u＋ （6S1/2 ＋ 6P1/2） state＊

In this paper, ultracold cesium molecules are formed through photoassociation technology, which is carried out in a magneto-optical trap. High resolution photoassociaion spectra with the rotational progressions up to J = 7 are obtained. Three rovibrational levels of the long-range 0＋ state of Cs2 below the （6S1/2 ＋ 6P1/2） dissociation limit are specifically investigated. By fitting their binding energy intervals to the non-rigid rotational model, the rotational constant of the long- range 0u＋ state is determined. A proportional dependence of the value of the rotational constant on the vibrational quantum number is demonstrated.     

Infrared diode laser spectroscopy of O2–N2O van der Waals complex in the v1 symmetric stretch region of N2O

The rovibrational spectrum of O2–N2O van der Waals complex is measured in the ν1 symmetric stretch region of N2 O monomer using a tunable diode laser spectrometer. The complex is generated by a slit-pulsed supersonic expansion with gas mixtures of O2, N2 O, and He. Both a- and b-type transitions are observed. The effective Hamiltonian for an open-shell complex consisting of a diatomic molecule in a ^3Σ electronic state and a closed-shell partner is used to analyze the observed spectrum. Molecular constants in the vibrationally excited state are determined accurately. The band-origin of the spectrum is determined to be 1284.7504（25） cm^-1, red-shifted from that of the N2 O monomer by ～ 0.1529 cm^-1.     

Molecular picture for X_0(2900) and X_1(2900)

Inspired by the newly observed X_0(2900) and X_1(2900) states at LHCb,the K~*■ and K■ interactions are studied in the quasipotential Bethe-Salpeter equation approach combined with the one-bo son-exchange model.The bound and virtual states from the interactions are searched for as poles in the complex energy plane of scattering amplitude.A bound state with I(J~P)=0(0~+) and a virtual state with 0(1~-) are produced from the K~*■ interaction and K■ interaction,and can be related to the X_0(2900) and X_1(2900) observed at LHCb,respectively.A bound state with I(J~P)=0(1~+) and a virtual state with I(J~P)=0(2~+) are also predicted from the K~*■ interaction,with the same α value,to reproduce the X_(0,1)(2900),which can be searched for in future experiments.     

Shapiro Steps in Flux-Trapped Surface Intrinsic Junctions of Bi2Sr2CaCu2O8＋δ

Microwave-field responses of the surface intrinsic Josephson junctions (IJJs) of Bi2Sr2CaCu2O8 δ superconductors are investigated. The IJJs are fabricated using an in situ low-temperature cleavage technique, which leads to the well-characterized surface CuO2 double layers and surface junctions. For the surface junctions in the largejunction limit, usually no Shapiro steps appear when a microwave field is applied. It is found that when the junctions are in a flux-trapped state, which is produced by a pulsed current and in which the critical current is significantly suppressed, clear Shapiro steps can be observed. These results are important for the study of the microwave-field properties of vortex-carrying IJJs and may find their use in device applications.     

Rotational Population Measurement of Ultracold ~(85)Rb~(133)Cs Molecules in the Lowest Vibrational Ground State

We measure the rotational populations of ultracold ~(85)Rb~(133) Cs molecules in the lowest vibrational ground state by a depletion spectroscopy and quantify the molecular production rate based on the measurement of single ion signal area. The ~(85)Rb~(133)Cs moleeules in the X~1∑~1(v=0) are formed from the short-range(2)~3∏_0+(v = 10, J = 0)molecular state. A home-made external-cavity diode laser is used as the depletion laser to measure the rotational populations of the formed molecules. Based on the determination of single ion signal, the production rates of molecules in the J = 0 and J = 2 rotational levels are derived to be 4800 mole/s and 7200 mole/s, respectively.The resolution and quantification of molecules in rotational states are facilitative for the manipulation of rotational quantum state of ultracold molecules.     

Dynamical study of the possible molecular state X（3872） with the s-channel one gluon exchange interaction

The recently observed X（3872） resonance, which is difficult to assign a conventional cc charmonium state in the quark model, may be interpreted as a molecular state. Such a molecular state is a hidden flavor four quark state because of its charmonium-like quantum numbers. The s-channel one gluon exchange is an interaction which only acts in the hidden flavor multi-quark system. In this paper, we will study the X（3872） and other similiar hidden flavor molecular states in a quark model by taking into account the s-channel one gluon exchange interaction.     

High-resolution photoassociation spectroscopy of ultracold Cs2 long-range 0g- state：The external well potential depth

High-resolution photoassociation spectroscopy is reported using a modulation spectroscopy technology in a cesium atomic magneto-optical trap. The two lowest vibrational levels have been experimentally observed which have been theoretically predicted in [Phys. Rev. A 75 052501(2007)]. A new potential curve is obtained by using the Rydberg–Klein–Ress method with a well depth of 82.384±0.026 cm-1, which is deeper than the result of previous experiment( 77.909 cm-1) and the theoretical prediction( 81.6445 cm-1).     

Ionization Detection of Ultracold Ground State Cesium Molecules

Photoassociation of ultracold atoms is an important method for producing stable ultracold molecules with extensive applications. Ion spectroscopy technique, which has higher sensitivity compared with trap loss spectroscopy and fragment spectroscopy, plays an important pole in the research of photoassociation spectroscopy. Based on ion spectroscopy technique, a complete experimental system is employed to produce and detect the ultracold ground state molecules, including the equipment of photoionization and time-of-fight mass spectroscopy. Ultracold ground state cesium molecules are demonstrated by the ionization detection technique. The number of the ground-state molecules produced in our MOT is measured. In addition, the relationship of the time interval of the cesium atom ion and the cesium molecular ion to the meta/grid voltage is studied for the optimization of the experimental parameters.     

Geometrical structures,vibrational frequencies,force constants and dissociation energies of isotopic water molecules （H2O,HDO, D2O,HTO, DTO,and T2O） under dipole electric field

The dissociation limits of isotopic water molecules are derived for the ground state. The equilibrium geometries, the vibrational frequencies, the force constants and the dissociation energies for the ground states of all isotopic water molecules under the dipole electric fields from -0.05 a.u. to 0.05 a.u. are calculated using B3P86/6-311++G(3df,3pf). The results show that when the dipole electric fields change from -0.05 a.u. to 0.05 a.u., the bond length of H-O increases whereas the bond angle of H-O-H decreases because of the charge transfer induced by the applied dipole electric field. The vibrational frequencies and the force constants of isotopic water molecules change under the influence of the strong external torque. The dissociation energies increase when the dipole electric fields change from -0.05 a.u. to 0.05 a.u. and the increased dissociation energies are in the order of H2O, HDO, HTO, D2O, DTO, and T2O under the same external electric fields.     

Vector correlations study of the reaction N(~2D) + H_2(X~1Σ_g~+) →NH(a~1?) + H(~2S) with different collision energies and reagent vibration excitations

Vector correlations of the reaction N(2D)+ H2(X1Σ+g) → NH(a1?)+ H(2S) are studied based on a recent DMBESEC PES for the first excited state of NH2[J. Phys. Chem. A 114 9644(2010)] by using a quasi-classical trajectory method.The effects of collision energy and the reagent initial vibrational excitation on cross section and product polarization are investigated for v = 0–5 and j = 0 states in a wide collision energy range(10–50 kcal/mol). The integral cross section could be increased by H2 vibration excitation remarkably based on the DMBE-SEC PES. The different phenomena of differential cross sections with different collision energies and reagent vibration excitations are explained. Particularly,the NH molecules are scattered mainly in the backward hemisphere at low vibration quantum number and evolve from backward to forward direction with increasing vibration quantum number, which could be explained by the fact that the vibrational excitation enlarges the H–H distance in the entrance channel, thus enhancing the probability of collision between N atom and H atom. A further study on product polarization demonstrates that the collision energy and vibrational excitation of the reagent remarkably influence the distributions of P(θr), P(φr), and P(θr, φr).     

Ab initio calculations on the spectroscopic constants, vibrational levels and classical turning points for the 21∏u state of dimer 7Li2

The accurate dissociation energy and harmonic frequency for the highly excited 2^1Пu state of dimer ^7Li2 have been calculated using a symmetry-adapted-cluster configuration-interaction method in complete active space. The calculated results are in excellent agreement with experimental measurements. The potential energy curves at numerous basis sets for this state are obtained over a wide internuclear separation range from about 2.4a0 to 37.0a0. And the conclusion is gained that the basis set 6-311＋＋G（d,p） is a most suitable one. The calculated spectroscopic constants De, Re, ωe, ωeχe, ae and Be at 6-311＋＋G（d,p） are 0.9670 eV, 0.3125 nm, 238.6 cm^-1, 1.3705 cm^-1, 0.0039 cm^-1 and 0.4921 cm^-1, respectively. The vibrational levels are calculated by solving the radial SchrSdinger equation of nuclear motion. A total of 53 vibrational levels are found and reported for the first time. The classical turning points have been computed. Comparing with the measurements, in which only the first nine vibrational levels have been obtained so far, the present calculations are very encouraging. A careful comparison of the present results of the parameters De and We with those obtained from previous theories clearly shows that the present calculations are much closer to the measurements than previous theoretical results, thus representing an improvement on the accuracy of the ab initio calculations of the potentials for this state.     

Total Cross Sections for Electron Scattering from the Isoelectronic （Z = 14） Molecules （C2H2, CO, HCN and N2） at 100－5000eV

A complex optical model potential correlated by the conception of bonded atom, which considers the overlapping effect of electron clouds between the two atoms in a molecule, is firstly employed to calculate the total cross sections for electron scattering from the isoelectronic (Z = 14) molecules (C2H2, CO, HCN, and N2) at 100-5000 eV using the additivity rule at the Hartree-Fock level. The difference between the bonded atom and the free one is that the overlapping effect of electron clouds of bonded atoms in molecules is considered. The quantitative molecular total cross section results are compared with the experimental data and with the other calculations wherever available and good agreement is obtained above 100 eV. It is shown that the additivity rule along with the complex optical model potential considering the overlapping effect of electron clouds can give the results better than that uncorrelated by it. The correlating calculations are much closer to the experiments than the spherical-complex-optical-potential results in the lower energy region [Phys. Rev. A 45 (1992) 202]. Therefore,considering the overlapping effect of electron clouds in the complex optical potential could be helpful for the better accuracy of the total cross section calculations of electron scattering from molecules.     

Reentrant Spin Glass Behaviour and CE-Type Antiferromagnetic Phase in Half Doping （La,Pr）1／2Ca1／2 MnO3 Manganites

The reentrant spin glass behaviour was observed in half doping (La,Pr)1/2Ca1/2MnO3 manganites with a CEtype antiferromagnetic structure. It shows sequential multiple magnetic transitions from the paramagnetic to the ferromagnetic, antiferromagnetic, spin glass (SG) transitions, which reflects the complex magnetic interaction in the ground state of manganites. This can be explained by the competition interaction between the ferromagnetic and the CE-type antiferromagnetic matrix, and the disorder due to the tolerance factor t and A-cation size variance σ^2. The results reveals the coexistence of ferromagnetic clusters and SG clusters in the background of the antiferromagnetic matrix in the ground state of half doping (Pr,La)1/2Ca1/2MnO3 systems.     

Microscopic Mechanism of the ω Variation in Moments of Inertia for the Yrast Superdeformed Bands ^194T1（1a,1b）

The variation in moments of inertia(J^(1)and J^(2) with rotational frequency for the superdeformed bands in odd-odd nuclei,194T1(1a,1b),is investigated by using the particle-number conserving method for treating the pairing interaction(monopole and quadrupole),The observed variations ofJ^(1) and J^(2) with ω are reproduced quite well in the calculation and the contributions from each major shell are clearly displayed.     

Investigation on the Cs 6S1/2to 7D elec trie quadrupole tr ansition via monochromatic two-photon process at 767 nm

We experimentally demonstrate the cesium electric quadrupole t ransition from the 6S_1/2ground st ate to the 7D_3/2,5/2excited state t hrough a virtu al level by using a single laser at 767 nm.The excited state energy level population is characterized by varying the laser power,the temperature of the vapor,and the polarization combinations of the laser beams.The optimized experimentai parameters are obtained for a high resolution transition interval identification.The magnetic dipole coupling constant A and elec trie quadrupole coupling constant B for the 7D_3/2,5/2states are precisely determined by using the hyperfine levels intervals.The results,A=7.39(0.06)MHz,B=-0.19(0.18)MHz for the 7D_3/2state,and A=-1.79(0.05)MHz,B=1.05(0.29)MHz for the 7D_5/2state,are in good agreement with the previous reported results.This work is beneficial for the determination of atomic structure information and parity non-conser vat ion,which paves the way for the field of precision measurements and atomic physics.     

Charge Density Wave States and Structural Transition in Layered Chalcogenide TaSe_(2-x)Te_x

The structural features and three-dimensional nature of the charge density wave(CDW) state of the layered chalcogenide 1 T-TaSe_(2-x)Te_x(0≤x≤2.0) are characterized by Cs-corrected transmission electron microscopy measurements. Notable changes of both average structure and the CDW state arising from Te substitution for Se are clearly demonstrated in samples with x 0.3. The commensurate CDW state characterized by the known star-of-David clustering in the 1 T-TaSe_2 crystal becomes visibly unstable with Te substitution and vanishes when x=0.3. The 1 T-TaSe_(2-x)Te_x(0.3≤x≤1.3) samples generalily adopt a remarkable incommensurate CDW state with monoclinic distortion, which could be fundamentally in correlation with the strong q-dependent electronphonon coupling-induced period-lattice-distortion as identified in TaTe2. Systematic analysis demonstrates that the occurrence of superconductivity is related to the suppression of the commensurate CDW phase and the presence of discommensuration is an evident structural feature observed in the superconducting samples.