Applications of Atomic and Molecular Theory to Calculations in Space Science and Engineering

A systematic elaboration is given on atomic and molecular theory problems encountered in dealing with space science and engineering. Three sections are presented in the paper on calculations for gas thermodynamic and transfer properties, characteristics of the optical radiation from the reentry' bodies, and the interaction between surfaces of man-made satellites and incident particles. Researches on them are much related to the fundamental problems regarding the atomic and molecular theory.

Preparation of Arbitrary Four-Qubit W State with Atomic Ensembles via Rydberg Blockade

The generation of various entangled states is an essential task in quantum information processing. Recently, a scheme （PRA 79, 022304） has been suggested for generating Greenberger-Horne-Zeilinger state and cluster state with atomic ensembles based on the Rydberg blockade. Using similar resources as the earlier scheme, here we propose an experimentally feasible scheme of preparing arbitrary four-qubit W class of maximally and non- maximally entangled states with atomic ensembles in a single step. Moreover, we carefully analyze the realistic noises and predict that four-qubit W states can be produced with high fidelity （F - 0.994） via our scheme.

Corrections to atomic ground state energy due to interaction between atomic electric quadrupole and optical field

We study the ground state energy of an atom interacting with an oscillating optical field with electric dipole and quadrupole coupling.Under the rotating wave approximation,we derive the effective atomic Hamiltonians of the dipole/quadrupole coupling term within the perturbation theory up to the second order.Based on the effective Hamiltonians,we analyze the atomic ground-state energy corrections of these two processes in detail.As an application,we find that for alkali-like atoms,the energy correction from the quadrupole coupling is negligible small in comparison with that from the dipole coupling,which justifies the so-called dipole approximation used in literatures.Some special cases where the quadrupole interaction may have considerable energy corrections are also discussed.Our results would be beneficial for the study of atom–light interaction beyond dipole approximation.

Studies of Atomic Structure and Physical Properties of Metal Clusters in MgO by HREM and Nano-probe Methods

Nanometer-sized metal clusters were prepared inside single crystalline MgO films by vacuum co-deposition of metals and MgO. The atomic structure was studied by high-resolution electron microscopy (HREM) and nm-area electron diffraction. The size of the clusters is ranging from 1 nm to 3 nm without those larger than 5 nm, and most of them have definite epitaxial orientations with the MgO matrix films. The character of the composite films is very much useful for the studies of various kinds of physical properties with anisotroPy. The physical properties such as electric transport, magnetic, optical absorption, sintering and catalytic ones were thus measured on the same samples analyzed by HREM by using high sensitivity apparatus with interest of clarifying the retationship between the atomic structure and physical properties

Ionization and Charge Transfer of Atomic Hydrogen by Highly Charged Ions

Cross sections for charge transfer and ionization of atomic hydrogen by highly charged ions A^q＋ （q =6 9） are evaluated using a simple and classical method based on the previous works by Bohr and Lindhard [K. Dan. Vidensk. Selsk. Mat. Fys. Medd 28 （1954） No 7], Brandt [Nucl. Instrum. Methods Phys. Res. 214 （1983） 93] and Ben-Itzhak et al. [J. Phys. B： At. Mol. Opt. Phys. 26 （1993） 1711]. It is proved that the present calculations are feasible to some extent in comparison with available experimental data and quantum calculations.

A Simple Remark Leading to a Basic Precision Estimate for Non-Relativistic (NR) Real Values of Quantum Mechanics Operators

Starting with a very basic statement that any physical constants cannot be written with an infinite precision, it is shown how to introduce this uncertainty into the Hamiltonian of non-relativistic atomic (NR) physics and how to estimate errors on quantum operators (energy, frequency, momenta) when an uncertainty is assigned to . The Schrödinger equation is written and the kinetic energy term is transformed into a Laplacian: . This transformation leads (as known since 1926) to the wave equation, whose solutions are wave functions. The relativity correction to the kinetic energy term is introduced and its effect is discussed. (h constant has an uncertainty value taken from CODATA.)

A Cosmological Model for the Early Universe: The Formation of Fundamental Particles

A cosmological model for the very early universe is proposed which may modify the present point of view of physicists and astrophysicists, concerning the very early universe at a miniscule fraction of a second, approximately 10-60 seconds after the Big Bang. The model proposes the presence of a primordial s-particle that, following the Big Bang, was violently ejected in all spatial directions together with extremely high-frequency radiation that dominates this era. The proposed s-particles underwent two geometrical phase transitions in space-time that led to the formation of the known fundamental particles (i.e., dark matter, quarks, electrons, neutrinos, etc.). Furthermore, in the model, the four fundamental forces may be accommodated within one structural framework. It shows that the electronic charge is not a fundamental quantity (intrinsic property of the particle), but rather that it can be derived from the tangential velocity of the s-particle. Moreover, it appears that the masses of the fundamental particles are proportional to the curvature of the path of the s-particle.

Using Gamma-Radiation for Drug Releasing from MWNT Vehicle

A drug delivery system via multi-walled carbon nanotube （MWNT） vehicle was synthesized in aqueous solution. MWNTs were first noncovalently functionalized with chitosan oligomers （CS） with a molecule weight of 4000-6000, making MWNTs water-soluble, and then a cancer ancillary drug tea polyphenols （TP） was conjugated mainly via the hydrogen bond between CS and TP molecules, making MWNTs efficient vehicle for drug delivering. The release of drug molecules can be realized by pH variation and γ-radiation, leading to new methods for controlling drug release from carbon nanotubes carrier. Due to the high penetrability of γ-rays, γ-radiation shows up new opportunities in controlled drug release, possibly facilitating the future cancer treatment in vivo.

Simulation of Chromium Atom Deposition Pattern in a Gaussain Laser Standing Wave with Different Laser Power

One-dimensional deposition of a neutral chromium atomic beam focused by a near-resonant Gaussian standing- laser field is discussed by using a fourth-order Runge-Kutta type algorithm. The deposition pattern of neutral chromium atoms in a laser standing wave with different laser power is discussed and the simulation result shows that the full width at half maximum （FWHM） of a nanometer stripe is 115nm and the contrast is 2.5：1 with laser power 3.93mW; the FWHM is 0.8nm and the contrast is 27：1 with laser power 16mW, the optimal laser power; but with laser power increasing to 50mW, the nanometer structure forms multi-crests and the quality worsens quickly with increasing laser power.

Coulomb Explosion and Energy Loss of Energetic C20 Clusters in Dense Plasmas

The molecular dynamics （MD） method is used to simulate the interactions of energetic C20 clusters with the dense plasma targets within the framework of the linear Vlasov-Poisson theory. The influences of various clusters （H2, N2, C20 and C60 respectively） on stopping power are discussed. The simulation results show that the vicinage effects in the Coulomb explosion dynamics and the stopping power are strongly affected by the variations in the cluster speed and the plasma parameters. Coulomb explosions are found to proceed faster for higher speeds, lower plasma densities and higher electron temperatures. In addition, the cluster stopping power is strongly enhanced in the early stages of Coulomb explosions due to the vicinage effect, but this enhancement eventually diminishes, after the cluster constituent ions are sufficiently separated. For the large and heavy clusters, the stopping power ratio reaches much higher values in the early stage of Coulomb explosion owing to the constructive interferences in the vicinage effect.

Rotational and Vibrational State Distributions of CsH and Relative Reactivity in Reactions of Cs（6^2D,7^2D） with H2

By using a pump-probe technique, the nascent rotational and vibrational state distributions of CsH are obtained in the Cs（6^2 D,7^2 D） plus H2 reaction. The nascent CsH molecules are found to populate the lowest two vibrational （v″ = 0 and 1） levels of the ground electronic state. By comparing the spectral intensities of the CsH action spectra with those of pertinent Cs atomic fluorescence excitation spectra, the relative reactivity with 1-12 is in an order of6^2D3/2 〉 6^2D5/2 〉 7^2D3/2 〉 7^2D5/2. The rotational temperatures are found to be slightly below the cell temperature. The relative fractions （〈fV〉, 〈fR〉, 〈fT〉） of average energy disposal are derived as （0.2,0.12,0.68）, （0.2,0.12,0.68）, （0.07,0.04,0.89） and （0.07,0.04,0.89） for the 6^2D3/2, 6^2D5/2, 7^2D3/2 and 7^2D5/2, respectively. The major available energy is released as translation. These results support that the reaction mechanism of Cs（6^2 D,7^2 D） plus 112 is primarily a eollinear abstraction and not an insertion.

Quantum Phase Transition of the Bosonic Atoms near the Feshbach Resonance in an Optical Lattice

The quantum phase transition from the Mott insulator to the superfluid phases of the bosonic atoms trapped in an optical lattice, in which the on-site interaction carl be tuned by a Feshbach resonance, is investigated by a variational approach within mean-field theory. We derive an extended Bos^Hubbard model to describe this ultracold atomic system. By theoretical calculation and analysis, the phase diagram is shown clearly, and we find an exciting and novel phenomenon that is the appearance of the Mort insulator-sea （MI-sea）. Meanwhile, the experimental feasibility of observing the MI-sea is discussed by analyzing the published data related to the Fashbaeh resonance at present. Finally, the potential application of the MI-sea for quantum information processing and quantum computation is also discussed in detail

Collision-Induced Coherence Effect on Coherent Population Transfer

We investigate the effect of collision-induced coherence on coherent population transfer with the stimulated Raman adiabatic passage technique in a double A-type four-level system with a widely separated excited doublet. It is shown that when the two pulsed lasers with Rabi frequencies nearly comparable to the energy separation of the doublet are tuned to the particular frequency where the condition for quantum interference is satisfied, the very low transfer efficiency due to the nonadiabatic coupling between the two degenerate adiabatic states could be enhanced significantly with the increase of the collisional decay rates in a moderate range. The enhanced transfer efficiency results from the weakening of the nonadiabatic coupling between the two degenerate adiabatic states realized through collision-induced destructive quantum interference.

Ground State of Fermions in a 1D Trap with δ Function Interaction

The ground state of fermions in a 1D trap with δ function interaction is studied mathematically with group theory ideas.

A Quasi-One-Dimensional Model for a Chain of Water Molecules on the Nanometer Scale

Water confined into the interior channels of narrow carbon nanotubes or transmembrane proteins can form collectively oriented molecular chains held together by tight hydrogen bonds. We develop a quasi-one-dimensional model for a chain of water molecules which interact with each other via the Coulomb and power-like repulsive interactions. We explore the equilibrium property of the water chain and derive an exact analytical expression for the total interaction energy of the water chain, denoted by W（0）int. It is found that W（0）int is minimal when the distance between the two neighboring water molecules in a hydrogen-bonded chain is equal to 0.265 nm. The model is expected to be useful for studying analytically the properties of single-file water molecules inside water channels, such as the concerted motion of water molecules.

Polarization Gradient Cooling by Zeeman-Effect-Assisted Saturated Absorption

A novel and simple method to realize polarization gradient cooling （PGC） is reported. The stabilizing, shifting and rapid tuning of the frequency of the external cavity diode laser is realized by using the Zeeman-effect-assisted Doppler-free saturated absorption technique. Based on this convenient technique, 87Rb cold atoms are captured from room-temperature background vapor in the magneto-optical trap （MOT）. Meanwhile, the steady-state number, the density and the lifetime of atoms in the MOT are measured. Subsequently, a frequency-fast-varying circuit is designed to realize PGC, which is demonstrated effectively and reliably in experiments. The temperature of the cold atom cloud is measured by two different methods, which coincide with each other.

An Experimental Observation of Axial Variation of Average Size of Methane Clusters in a Gas Jet

Axial variation of average size of methane clusters in a gas jet produced by supersonic expansion of methane through a cylindrical nozzle of 0.8 mm in diameter is observed using a Rayleigh scattering method. The scattered light intensity exhibits a power scaling on the backing pressure ranging from 16 to 50bar, and the power is strongly Z dependent varying from 8.4 （Z = 3mm） to 5.4 （Z = 11mm）, which is much larger than that of the argon cluster. The scattered light intensity versus axial position shows that the position of 5mm has the maximum signal intensity. The estimation of the average cluster size on axial position Z indicates that the cluster growth process goes forward until the maximum average cluster size is reached at Z - 9 mm, and the average cluster size will decrease gradually for Z 〉 9 mm.

Differential and Integral Cross Sections for Electron Impact Excitation of Lithium

The differential and integral cross sections for electron impact excitation of lithium from the ground state 1s22s to excited states 1s22p, 1s23l （l=s, p, d） and 1s24l （l=s, p, d, f）at incident energies ranging from 5 eV to 25 eV are calculated by using a full relativistic distorted wave method. The target state wavefunctions are calculated by using the Grasp92 code. The continuum orbitals are computed in the distorted-wave approximation, in which the direct and exchange potentials among all the electrons are included. A part of the cross sections are compared with the available experimental data and with the previous theoretical values. It is found that, for the integral cross sections, the present calculations are in good agreement with the time-independent distorted wave method calculation, for differential cross sections, our results agree with the experimental data very well.

Fidelity of quantum state for interacting system of light field and atomic Bose-Einstein condensate

The evolution characteristics of quantum state fidelity in an interacting system of single-mode light field and atomic Bose-Einstein condensate have been studied and the influence of the initial light field intensity and the interaction among atoms of Bose-Einstein condensate on the quantum state fidelity respectively have been discussed.

Absorption-amplification response with or withoutspontaneously generated coherence effectin a four-level atomic system

We discuss and analyze the absorption properties of a weak probe field in a typical four-level atomic system in the presence of a spontaneously generated coherence (SGC) term. The influences of the SGC and a coherent pump field on the probe absorption-amplification are investigated. The results show that the absorption of such a weak probe field can be dramatically enhanced due to the SGC effect. At the same time, the probe-absorption profile exhibits a two-peak structure and the probe-absorption peak gradually decreases as the pump intensity increases. On the contrary, the amplification of such a weak probe field near the line center of the probe transition can be achieved by adjusting the coherent pump field intensity in the absence of the SGC effect.