Radiative Energy Shifts of an Atom Coupled to the Derivative of a Scalar Field near a Reflecting Boundary

We study the radiative energy level shifts of a two-level atom in dipole coupling to the derivative of a massless scalar quantum field in a spacetime with a perfectly reflecting boundary, and calculate the contributions of vacuum fluctuations and radiation reaction to the level shift. It is found that the energy level shift of the excited state is an oscillating function of the atom＇s distance from the boundary and it can either be positive or negative, while that of the ground state is always positive. The most remarkable feature is that the energy level shift of the ground state behaves like 1/z^4 when the atom＇s distance from the boundary, z, is very large as compared to the transition wavelength of the atom, while it behaves like 1/z^3 when z is very small     

Analysis of the influence shifts of the acetylene of various effects on frequency saturated absorption lines

Frequency shifts of the acetylene saturated absorption lines at 1.5μm with temperature, gas pressure and laser power have been investigated in detail. The second-order Doppler effect, the recoil effect, the Zeeman effect, the pressure shift and the power shift are taken into consideration. The magnitudes of those shifts caused by various effects are evaluated. In order to reproduce the stability of 5.7 × 10^-14 obtained by Edwards, all necessary conditions are given. The results show that when there is a larger external magnetic field, the Zeeman shift could not be neglected, so that the shield should be employed. And the design of a long cavity is advantageous to reduce the influence of the second-order Doppler effect. The results also show that at least 4-2.5℃ temperature control for cavity can effectively prevent several effects and improve the frequency stability.     

Properties of Linear Entropy in k-Photon Jaynes-Cummings Model with Stark Shift and Kerr-Like Medium

The time evolution of the linear entropy of an taking into consideration Stark shift and Kerr-like medium. atom in k-photon daynes-Cummings model is investigated The effect of both the Stark shift and Kerr-like medium on the linear entropy is analyzed using a numerical technique for the field initially in coherent state and in even coherent state. The results show that the presence of the Kerr-like medium and Stark shift has an important effect on the properties of the entropy and entanglement. It is also shown that the setting of the initial state plays a significant role in the evolution of the linear entropy and entanglement.     

Observation of the BEC-BCS crossover in a degenerate Fermi gas of lithium atoms

We observe characteristic atomic behaviors in the Bose-Einstein-condensation-Bardeen-Cooper-Schrieffer(BEC-BCS)crossover,by accurately tuning the magnetic field across the Feshbach resonance of lithium atoms.The magnetic field is calibrated by measuring the Zeeman shift of the optical transition.A non-monotonic anisotropic expansion is observed across the Feshbach resonance.The density distribution is explored in different interacting regimes,where a condensate of diatomic molecules forms in the BEC limit with the indication of a bimodal distribution.We also measure the three-body recombination atom loss in the BEC-BCS crossover,and find that the magnetic field of the maximum atom loss is in the BEC limit and gets closer to the Feshbach resonance when decreasing the atom temperature,which agrees with previous experiments and theoretical prediction.This work builds up a controllable platform for the study on the strongly interacting Fermi gas.     

Entropy squeezing of the field interacting with a nearly degenerate V-type three-level atom

The position- and momentum-entopic squeezing properties of the optical field in the system of a nearly degenerate three-level atom interacting with a single-mode field are investigated. Calculation results indicate that when the field is initially in the vacuum state, it may lead to squeezing of the position entropy or the momentum entropy of the field if the atom is prepared properly. The effects of initial atomic state and the splitting of the excited levels of the atom on field entropies are discussed in this case. When the initial field is in a coherent state, we find that position-entropy squeezing of the field is present even if the atom is prepared in the ground state. By comparing the variance squeezing and entropy squeezing of the field we confirm that entropy is more sensitive than variance in measuring quantum fluctuations.     

Effects of Anisotropy on Pair-wise Entanglement of a Four-Qubit Heisenberg XXZ Chain

The pair-wise thermal entanglement in a four-qubit Heisenberg XXZ chain ＆ investigated to study the role of anisotropy when an external magnetic field is included. It is found that pair-wise entanglement is absent between nearest- and next-nearest neighbouring qubits with anisotropic parameter △≤-1. For two nearest-neighbouring qubits, increasing the parameter can not only induce the entanglement, but also extend the entanglement region in terms of magnetic field B and temperature T. For two next-nearest-neighbouring qubits, increasing anisotropic parameter can shift the location of the entanglement and control the extent of the entanglement in terms of magnetic field at a finite temperature.     

Effect of Quenching on the Grain Boundary Relaxation in PM2000 ODS Alloy

Grain boundary relaxation in a Fe-based ODS alloy is studied by internal friction measurements. It is found that a grain-boundary peak appears at a lower temperature in the quenched specimens than that in the annealed specimens. The activation energy of the peak is H=2.82±0.11 eV for the former while H = 2.53±0.08 eV for the latter. In addition, a new relaxation peak is observed at the high temperature side of the grain boundary peak in the quenched specimens with an activation energy of 4.41±0.25 eV. The height of the peak increases with increasing quenching temperature. The results suggest that both the shift of the grain-boundary peak and the appearance of the new peak are due to increasing vacancies by quenching that are favourable for the motion of the grain boundaries.     

Entanglement Dynamics of a Three-Level Atom in Ξ Configuration

Dynamical behaviour of entanglement between the cavity mode and a three-level atom in the configuration is studied by making use of log-negativity. The influence of initial temperature of the thermal field and detuning on the entanglement is investigated. It is found that the maximal values of entanglement decreases with the temperature of the thermal field and can be controlled by the defaming.     

Entropy squeezing and atomic inversion in the h-photon Jaynes-Cummings model in the presence of the Stark shift and a Kerr medium： A full nonlinear approach

The interaction between a two-level atom and a single-mode field in the k-photon Jaynes-Cummings model （JCM） in the presence of the Stark shift and a Kerr medium is studied. All terms in the Hamiltonian, such as the single-mode field, its interaction with the atom, the contribution of the Stark shift and the Kerr medium effects are considered to be f-deformed. In particular, the effect of the initial state of the radiation field on the dynamical evolution of some physical properties such as atomic inversion and entropy squeezing are investigated by considering different initial field states （coherent, squeezed and thermal states）.     

A Lower Bound on the Entanglement in the Jaynes-Cummings Model

The entanglement between an atom and field is investigated by using the 3aynes-Cummings model. The initial atomic state is supposed in a mixed state and the field is in a squeezed state. The lower bound on the entanglement quantified by concurrence is calculated. It is found that the entanglement with the atom being initially in a mixed state can be larger than that with the atom being initially in a pure state. The entanglement is not a monotone function of the squeezing parameter r of the field and it achieves the maximum for certain r and then decreases with further increase of r.     

Ground-state energy of pionic hydrogen to one loop

We investigate the ground-state energy of the atom (pionic hydrogen) in the framework of QCD + QED. In particular, we evaluate the strong energy-level shift. We perform the calculation at next-to-leading order in the low-energy expansion in the framework of the relevant effective field theory. The result provides a relation between the strong energy shift and the pion-nucleon S-wave scattering lengths - evaluated in pure QCD - at next-to-leading order in isospin-breaking and in the low-energy expansion. We compare our result with available model calculations. Received: 11 June 2002 / Published online: 9 October 2002     

Anomalous behavior of the structural parameters of YBa2Cu4O8 single crystals at the transition to the superconducting state

High-precision x-ray crystallographic studies of YBa₂Cu₄O₈ single crystals (T _c =70 K) are performed at eight temperatures in the interval 20–295 K. It is found that a number of structural parameters exhibit anomalous behavior near the superconducting transition of the crystal. A characteristic effect near the phase transition is the displacement of the O1 bridge atom that joins the Cu1 atom of the cuprate chain to the Cu2 atom of the cuprate plane. The shift of this oxygen toward the Cu2 atom is indicative of a change in the Cu2-O1 chemical bond and of charge transfer to the cuprate plane in the process of the transition of the crystal to the superconducting state. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 7, 502–506 (10 October 1997)     

Energy-Level Shifts of a One-Electron Atom in Higher-Derivative Gravitational Field Caused by High-Power Laser Pulse

The gravitational field produced by a high-power laser pulse traveling with a velocity < c is found in the framework of higher-derivative theory of gravitation. The gravitational perturbations of the energy levels of a freely falling one-electron atom in the higher-derivative gravitational field are studied. The energy-level shifts of highly excited hydrogen atom are considered, and the influence of the additional forces included in the linearized higher-derivative gravitation on the energe level shifts of the atom is investigated.     

Magnetic properties of small amounts of iron dissolved in copper palladium alloys

The magnetic susceptibilities of copper-rich Cu_1−x Pd _x Fe _y alloys,x=0−0.40,y=30−300 ppm, have been measured in the temperature range 1.7 K–300 K. The results imply that an iron atom induces a magnetic moment of about 0.35μ _B on a nearest neighbour palladium atom. Conversely the effect of the nearest neighbour palladium atom on the iron atom itself leads to a stabilization of the iron moment indicated by a lowering of its Kondo temperature.     

Self-interstitial configuration in molybdenum studied by modified analytical embedded atom method

The stability of various atomic configurations containing a self-interstitial atom (SIA) in a model representing Mo has been investigated using the modified analytical embedded atom method (MAEAM). The lattice relaxations are treated with the molecular dynamics (MD) simulation at absolute zero of temperature. Six relatively stable self-interstitial configurations and formation energies have been described and calculated. The results indicate that the [111] dumbbell interstitial S₁₁₁ has the lowest formation energy, and in ascending order, the sequence of the configurations is predicted to be S₁₁₁, C, S₁₁₀, T, S₀₀₁ and O. From relaxed displacement field up to the fifth-NN atoms of six configurations, we know that the relaxed displacements depend not only on separation distances of the NN atoms from the defect centre but also strongly on the direction of the connected line between the NN atoms and the defect centre. The equilibrium distances between two nearest atoms in the core of the S₁₁₁, C, S₁₁₀, T, S₀₀₁ and O configurations are 0.72a, 0.72a, 0.71a, 0.72a, 0.70a and 0.70a, respectively.      

Susceptibility and electric dipole in metal C 60 compounds

The permanent electric dipole moment of metal atom-C₆₀ compounds is measured. A column (alkali) and a row (transition metals) of the periodic table are systematically investigated. Most of the experimental results are obtained at high temperature when the atom is mobile on the C₆₀ cage. For a given example (NaC₆₀), the dipole moment is also measured by a different method at low temperature and both results are consistent. For alkali, the results are compared to ab initio calculations. A good agreement is obtained, both for absolute values and for the evolution of the bonding in the alkali column. For transition metals, the relative values of the dipole moments are in qualitative agreement with the ionic character of the compounds.     

Interpretation of the isomer shift of interstitially implanted119Sn impurities in group IV semiconductors

Recent Mössbauer measurements of the isomer shift of interstitially implanted¹¹⁹Sn impurities in group IV semiconductors are interpreted in terms of the electron contact density of compressed Sn atoms and ions, respectively. The finite space allowed to the impurity atom in the host crystal is approximated by a Wigner-Seitz sphere. Using a calibration procedure, the dependence of the isomer shift on the Wigner-Seitz radiusR _A has been calculated for several electron configurations of the tin atom (ion). The isomer shift values for¹¹⁹Sn interstitials in diamond, silicon, germanium, and -tin are found to correspond to compressed, neutral tin atoms; furthermore, the relaxation of the host lattice about the impurity Sn atom is discussed.     

The Study on the Arc Plasma Temperature Measurement by Optical Emission Spectroscopy with Fiber Optical Transmission

Abstract

A method for transmitting radiation of the arc plasma with multimode fused quartz fiber onto the spectrograph has been studied. The plot of the Boltzmann function in emission spectral analysis is used for measuring temperature of the arc plasma. The measured temperature of the arc plasma is 5946.6K from least square linear regression of ln[λI/(gA)] and E_i for a number of the emission line intensities of the excited copper atom. Its regression coefficient and measured precision are ?0.97% and 1.7%, respectively. The advantages of the method of the diagnostic temperature for the arc plasma are absolute measurements of the temperature, remote sensing, precision and suitable for mal-environment, such as high temperature, toxic, explosion, strong magnetic or/and electrical fields.

In addition, we have discussed the effect of the spectroscopic constants, such as transition probability, A , the statistical weight of the upper level, g , and the energy of the upper level, E_i , of copper lines on calculating temperature with a plot of the Boltzmann function in detail. The results show that the accurate measurement of the temperature for the arc plasma is obtained only when the spectroscopic constants are selected correctly.     

Nuclear quadrupole resonance of norephedrine

Toward searching for illegal drugs, we investigated the pulsed nuclear quadrupole resonance (NQR) response of ¹⁴N in (1R,2S)-(-)-norephedrine, based on the predictions of quantum chemical calculations. Two pairs of spectral lines (ν₊=3.089, 3.093 MHz and ν₋=2.594, 2.608 MHz) were observed despite its molecule structure having only a single nitrogen atom. This indicates that the molecular crystal has two nonequivalent nitrogen atoms in the unit cell. The temperature dependence of the NQR frequencies and relaxation properties were investigated for the purpose of accurate remote sensing of the drugs. The NQR frequency shift was approximately 0.23 kHz/K around room temperature. The spin-lattice relaxation and spin-phase memory times were 5.2–10.2 ms and 0.6–1.5 ms, respectively.     

An adiabatic energy-level expression for anharmonic hydrogen-bonded systems

An adiabatic energy-level expression is obtained for hydrogen-bonded systems X-H----Y without neglecting the anharmonicity of the proton motion, treating the anharmonicity of the X----Y motion perturbatively or omitting many of the terms that couple the fast and slow motions. The energy-level expression is applied to FH----O (CH₃)₂. The reliability of the adiabatic energy-level expression is tested by comparing the adiabatic energy levels with variational energy levels.