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At the interface of van der Waals heterostructures, the crystal symmetry and the electronic structure can be reconstructed, giving rise to physical properties superior to or absent in parent materials. Here by studying a Bernal bilayer graphene moiré superlattice encapsulated by 30°-twisted boron nitride flakes, we report an unprecedented ferroelectric polarization with the areal charge density up to 1013 cm−2, which is far beyond the capacity of a moiré band. The translated polarization ~5 pC m−1is among the highest interfacial ferroelectrics engineered by artificially stacking van der Waals crystals. The gate-specific ferroelectricity and co-occurring anomalous screening are further visualized via Landau levels, and remain robust for Fermi surfaces outside moiré bands, confirming their independence on correlated electrons. We also find that the gate-specific resistance hysteresis loops could be turned off by the other gate, providing an additional control knob. Furthermore, the ferroelectric switching can be applied to intrinsic properties such as topological valley current. Overall, the gate-specific ferroelectricity with strongly enhanced charge polarization may encourage more explorations to optimize and enrich this novel class of ferroelectricity, and promote device applications for ferroelectric switching of various quantum phenomena.

Two-dimensional inorganic salt films have increasing potential in laboratory and industrial applications. However, the methods for fabricating these films are complicated and not appliable under ambient conditions, which extremely limits their applications. Here, we report a novel ultrathin NaNO3 flake with a thickness of less than 1.0 nm on a highly oriented pyrolytic graphite (HOPG) surface mediated by water. We note that neither molten salt nor water is affinitive to the aged carbon-based surface so that they form droplets on the HOPG surfaces. Interestingly, the solution formed by the mixture of salt and water develops an affinity toward the HOPG. Further, the flakes had adjustable electric conductivity. Density functional computation showed that water substantially increased the ionic bond length between NO3- to Na+, enhancing the interaction between the NaNO3 cluster and graphene via cation-π interaction, and rendering the mixture of water and NaNO3 graphene-philic toward the graphitic surface. The findings provide a brand-new way to obtain thin films of inorganic salts.

The origin of an injected charge and its temperature dependence in ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) thin films is studied by multimode scanning probe microscopy. During the poling process in scanning probe microscope (SPM) measurement, which is a local bias applied by using a conductive tip on a film’s surface to induce polarization orientation, a strong charge injection is always observed in oxide ferroelectric films; therefore, the surface potential is dominated by injection charge rather than polarization and screening charge. The surface potential shows an increase with the increase in the applied bias and saturation at a higher bias, which is much higher than the coercive field in PZT films. The positive surface potential shows a clear increase after oxygen plasma treatment, suggesting that the injection behavior is significantly enhanced. Subsequent heating could recover the surface condition to the initial state. Charge injection could be weakened but could not be completely eliminated by heat treatment. The current results suggest that charge injection behavior could not be easily relaxed, and a careful control of the localized poling process using an SPM conductive tip is required especially for studying the charge state on the surfaces of ferroelectric thin films.

A sharply peaked structure is found in the angular distribution of emitted $\pi^+$ mesons from the photon-proton collisions. It offers a possible way for generating a $\pi^+$-condensation in free space. To make the stimulated emission of $\pi^+$-mesons efficient, a ring resonator is designed., Comment: 4 pages,3 figures

The flat-topped beam is a special beam with wide applications in the directional backlight autostereoscopic display, and it is used as a directional backlight in the horizontal direction. However, it is still challenge to white light flat-topped beams with the traditional flat-topped beam shaper. In this paper, it is proposed that diffraction mask with butterfly-shaped hole arrays and cylindrical lens be used to produce the horizontal flat-topped white beams. The surface of the LCD backlight mask is covered by a layer of diffraction mask, where the butterfly-shaped holes are arranged in line along the vertical direction. Simultaneously, the height and width, hole center height are kept identical, and the ratio between the center depth and the perimeter of butterfly-shape hole is defined as the concavity. A flat convex cylindrical lens is placed in front of diffraction mask gaplessly. The uniform light field from LCD backlight is transformed into the white light flat-topped beams and projected on the receiving screen by the diffraction mask and cylindrical lens. Based on the Huygens-Fresnel diffraction integral, the intensity distribution formula of diffraction of the single wavelength light source on the receiving screen is derived. Furthermore, the intensity distribution formula on the screen is derived by super positioning the multiple wavelengths. The proposed method is verified by both numerical simulation and experimental validation. Numerical simulations elucidate the effects of the different transmission distance and butterfly hole concavity on the white light flat-topped beam flat-topped factor. The stimulated results show that the propagation distance does not influence the white light beam transverse intensity distribution characteristics of flat top. With the beam propagation distance increasing, the horizontal width of flat-topped beam becomes larger. When the concavity of the butterfly hole decreases, light intensity distribution shifts from Gaussian to flat type. However, the flat-topped factor decreases when the butterfly concavity is too small. The optimal concavity varies from 0.4 to 0.6, where the flattened factor of the transverse flat-topped beams reaches 0.89. In the experiments, films are produced with the diffraction of butterfly hole array mask. The height and width of butterfly are both 48 μm, and the concavities of the butterfly are 1, 0.83, 0.66 and 0.83 respectively. The cylindrical lens adopts PMMA cylindrical lens grating plate, with a thickness of 8 mm, a grating density for 18 line/inch, and the cylindrical lens curvature radius R is 2.67 mm. The experimental results show that the beam transmission is consistent with the result of numerical simulation. When concavity of the butterfly is 0.5, the flat factors of the white light horizontal of flat-topped beams are higher than 0.89 in a range from 500 mm to 2000 mm. Moreover, we also discuss the dispersion effects of shaft flat-topped beams and off-axis flat-topped beams, showing that the refraction and dispersion of the cylindrical lens can cancel out each other, so that the horizontal flat-toped white beams is basically dispersionless.

Using a variational method, we derive the optimal population distribution of angular momentum eigenstates for any given population range in a rotational wavepacket within the field-free cyclic state orientation framework. Correspondingly, we devise a train of half-cycle pulse clusters to purposively make the structure of the computed wavepacket approach the optimal population distribution, so that we can now utilize much more powerful means to realize an ideal orientation goal.

We show that the conservation and the non-additivity of the information, together with the additivity of the entropy make the entropy increase in an isolated system. The collapse of the entangled quantum state offers an example of the information non-additivity. Nevertheless, the later is also true in other fields, in which the interaction information is important. Examples are classical statistical mechanics, social statistics and financial processes. The second law of thermodynamics is thus proven in its most general form. It is exactly true, not only in quantum and classical physics but also in other processes, in which the information is conservative and non-additive., Comment: 4 pages

We show that two trains of half-cycle pulses (HCPs) with different amplitudes irradiating alternately on polar molecules can achieve a remarkable enhancement of field-free orientation compared with the case of an equal amplitude HCPs train for the same pulse separation. This kind of orientation enhancements is mainly due to an optimal adjustment of the population distribution on every field-free angular momentum eigenstate, in which the populations on the undesired states of high angular momenta are effectively suppressed, and the populations on the desired states of low angular momenta are correspondingly promoted.

The product rotational polarization of the ion-molecule reactions of D − + H 2 → H − + HD and H − + D 2 → D − + HD has been calculated by means of the quasi-classical trajectory method on a potential energy surface (PES) constructed by Panda and Sathyamurthy [J. Chem. Phys. 121, 9343 (2004)]. Comparing the dynamics of D − + H 2 → H − + HD with H − + D 2 → D − + HD, four polarization dependent generalized differential cross-sections (2π/ σ )(d σ 00 /d ω t ), (2π/ σ )(d σ 20 /d ω t ), (2π/ σ )(d σ 22+ /d ω t ), (2π/ σ )(d σ 21− /d ω t ) have been presented in the center of mass frame, respectively. The distribution of dihedral angle p ( ϕ r ), the distribution of angle between k and j ′, p ( θ r ), and the angular distribution of product rotational vectors in the form of polar plots in θ r and ϕ r are calculated as well. A pronounced isotopic effect is also revealed. It may be ascribed to the significant difference of the effective potential barrier height or the difference of the mass factor in the two reactions.

We investigate the high-order harmonic generation from an atom prepared in a superposition of ground state and highly excited state. When the atom is irradiated by an ultrashort pulse, the cutoff position of the plateau in the harmonic spectrum is largely extended compared with the case that the atom is initially in the ground state. The physics of the extension of the high-order harmonic plateau can be interpreted by the spatial structure of the atomic initial wave packet. We can optimize the generation of high-order harmonics by substituting the excited state for a particular coherent superposition of some highly excited states to form a spatially localized excited wave packet.

Electronic structures of PbMoO4 crystals containing F-type colour centres with the lattice structure optimized are studied within the framework of the fully relativistic self-consistent Direc–Slater theory, using a numerically discrete variational (DV-Xα) method. The calculated results show that F and F+ centres have donor energy levels in the forbidden band. The optical transition energies are 2.166 eV and 2.197 eV, respectively, corresponding to the 580 nm absorption bands in PbMoO4 crystal. The 580 nm absorption band in PbMoO4 is originated from the F-type colour centres.

The possible defect models of Y3+:PbWO4 crystals are discussed by defect chemistry and the most possible substituting positions of the impurity Y3+ ions are studied by using the general utility lattice program (GULP). The calculated results indicate that in the lightly doped Y3+:PWO crystal, the main compensating mechanism is [2YPb++VPb2−], and in the heavily doped Y3+:PWO crystal, it will bring interstitial oxygen ions to compensate the positive electricity caused by YPb+, forming defect clusters of [2YPb++Oi2−] in the crystal. The electronic structures of Y3+:PWO with different defect models are calculated using the DV-Xα method. It can be concluded from the electronic structures that, for lightly doped cases, the energy gap of the crystal would be broadened and the 420 nm absorption band will be restricted; for heavily doped cases, because of the existence of interstitial oxygen ions, it can bring a new absorption band and reduce the radiation hardness of the crystal.

Recently, two papers presented by Ortigoso et al. [Phys. Rev. Lett. 93 (2004) 073001 and Phys. Rev. A 72 (2005) 053401] develop a novel strategy in which the best sustainable molecular alignment/orientation has been achieved. We intend to analyse the dynamic mechanisms, including those Ortigoso et al. have not clarified.

Electronic structures of PbWO4 crystals containing F-type colour centres with the lattice structure optimized are studied within the framework of the fully relativistic self-consistent Dirac–Slater theory, using a numerically discrete variational (DV-Xα) method. The calculated results show that F and F+ centres have donor energy levels in the forbidden bands. Their optical transition energies are 1.84 eV and 2.21 eV, respectively, which correspond to the 680 nm and 550 nm absorption bands. It is predicted that the 680 nm and 550 nm absorption bands originate from the F and F+ centres in PbWO4 crystals.

The electronic structures, dielectric functions, complex refractive index and absorption spectra for the PbWO4 (PWO) crystal with and without oxygen vacancy VO2+ have been calculated using the full-potential (linearized) augmented planewave (FP-LAPW)+local orbitals (LO) method with the lattice structure optimized. The calculated results indicate that the optical properties of the PWO crystal show anisotropy and its optical symmetry coincides with the lattice structure geometry of the PWO crystal. The calculated absorption spectra indicate that the stoichiometric PWO crystal does not display absorption band in the visible and near-ultraviolet range. However, in this range, the absorption spectra of the PWO crystal containing VO2+ exhibit two peaks at 3.35eV (370nm) and 2.95eV (420nm), respectively. It is revealed that the 350nm and 420nm absorption bands are related to the existence of VO2+ in the PWO crystal.

We present a high-order harmonic generation (HHG) spectrum from a united two-atom system exposed to a combined laser pulse, by numerically solving a one-dimensional time-dependent Schrodinger equation. The combined laser pulse is composed of a low-frequency femtosecond pulse and a high-frequency attosecond one with respective appropriate amplitudes. For a suitable inter-nuclear separation, the harmonic emission efficiencies near the second cutoff of the extended plateau can be effectively enhanced by more than four orders of magnitude compared with the case of the low-frequency pulse alone. Such a combined pulse irradiating on the united two-atom system ionizes each atom, in a large rate (but not to a too large ionization yield), mainly at a particular time-interval. When the ionized electron from an atom reaches at the vicinity of the other atom and recombines with it, significant HHG enhancement is achieved for particular harmonics. This result, to our knowledge, is one of the best up to now in the endeavor for dramatically extending the width and simultaneously enhancing the height of the plateau.

We present the high-order harmonic generation spectrum from a united two-atom system simultaneously exposed to a fundamental Ti:sapphire and its 33rd harmonic (H33) lasers by numerically solving a one-dimensional time-dependent Schrodinger equation. At a suitable inter-nuclear separation, the harmonic plateau is widened from Ip+3.2Up in the single-atom case up to Ip+5.6Up in the united-atom case. Furthermore, the plateau is heightened in excess of six orders of magnitude by using the combined lasers compared with the case of the fundamental laser alone. Such a scheme can step by step accomplish the following processes: through a single H33 photon resonance transition an appropriate amount of electrons are first populated to an excited state, in which the electrons are easily ionized and subsequently accelerated by the fundamental laser; then they can recombine with the neighbouring atom, so that high-efficiency emissions of the harmonics beyond Ip+3.2Up are successfully realized.

We present a scheme aiming at the field-free orientation of molecules with smaller permanent dipole moments under the framework of the half-cycle pulse (HCP) method. Taking the HCCCl molecule as an example, we show that a train of identical HCPs with special time intervals can considerably raise the level of the orientation. The scheme is analytically interpreted in terms of intermittent Rabi oscillations by referring to a simplified two-state model.

The electronic structures, dielectric functions, complex refractive indices and absorption spectra for a perfect PbWO4 (PWO) crystal and the PWO crystals containing lead vacancy VPb2− have been calculated using a full-potential (linearized) augmented plane-wave (LAPW) + local orbitals (LO) method with the lattice structure optimized. The peaks of the absorption spectra corresponding to the electronic transitions have been studied. The calculated results indicate that the absorption band of the perfect PWO crystal does not occur in the visible region. However, the PWO crystal containing VPb2− has two additional absorption bands in this region. The two bands can be well decomposed into four gaussian-shape bands peaking at 350 nm, 405 nm, 550 nm and 670 nm, respectively, which coincide well with the 350 nm, 420 nm, 550 nm and 680 nm absorption bands measured in PWO crystals. Therefore, it can be concluded that the 350 nm, 420 nm, 550 nm and 680 nm absorption bands are related to the existence of VPb2− in the PWO crystal.

The electronic structures for three types of PbWO4 (PWO) crystals, the perfect PWO, the PWO containing lead vacancy (PWO-VPb) and fluorine doped PWO crystal (F−:PWO), are systematically studied within the framework of density functional theory. The computational results show that the Pb 6s state situates below the valence band so that Pb2+ ions are unable to trap holes forming Pb3+ or Pb4+ to compensate for VPb2−. The hole-trappers in PWO-VPb are O2− ions. Two of the longer-bond O2− ions share a hole forming O23−, and four of the longer-bond oxygen ions trap two holes forming an associated color centre [O23−-VPb-O23−], which may be the origin of the 420 nm absorption band. It is also concluded that the doping of F− would reduce the band gap and F− ions substituting for O2− can effectively restrict the formation of [O23−-VPb-O23−] and weaken the 420 nm absorption band and hence enhance the scintillation property of PWO.

The lattice structures around one lead vacancy VPb2− in PbWO4 are studied within the framework of the full-relativistic density functional theory. Using the conjugate gradient method, we optimize the geometry of the ions around VPb2− by moving the ions within the sub-cell until specified tolerance is satisfied. We obtain the geometric positions of ions around VPb2− after optimization. The calculated results indicate that there would be local lattice distortion caused by the existence of VPb2−. The electronic structures of both the optimized and pre-optimized PWO containing VPb2− have been calculated. The density of states of the distorted PWO indicates that the energy gap between the 2p state of O2− and the 5d state of W6+ is 3.90 eV, which shows that the distorted W–O tetrahedron may be the 420 nm luminescence centre.

We present high-order harmonic generation spectra resulted from a single-electron model molecular ion exposed to intense laser fields by numerically solving a one-dimensional time-dependent Schr?dinger equation. There are three plateaus in the spectra and the maximal cutoff energy is Ip+8.5Up, when the inter-nuclear distance R equals ??0/2. Here Ip is the ionization potential and Up = E02/(4?2) is the ponderomotive potential with E0 and ? being the laser electric field amplitude and the central frequency. The harmonic structures are well interpreted by a modified three-step model in which the effects of the electron reflected by the non-parent ion are stressed.

We propose a new version of the relativistic mean field theory for nuclear matter. The theory is based on an effective relativistic Lagrangian, in which, besides interactions via exchange mesons, baryons also interact with each other directly. The direct interaction is introduced to represent the compositeness of the baryon and to simulate the quark-quark interaction between them.

The binding energies per-nucleon for 1654 nuclei, whose mass numbers range from 16 to 263 and charge numbers range from 8 to 106, are calculated by the relativistic mean field theory, with finite nucleon size effect being taken into account. The calculated energy surface goes through the middle of experimental points, and the root mean square deviation for the binding energies per-nucleon is 0.08163 MeV. The numerical results may be well simulated by a droplet model type mass formula. The droplet model is therefore put on the relativistic mean field theoretical foundations.

The possibility of $\gamma-$ray laser generation by the radiation of wiggling electrons in an usual background laser is discussed., Comment: 9 pages,3 figures

Using the Hamiltonian lattice gauge theory, we perform some variational calculations to obtain the ground-state energy of SU(3) gauge field and scalar (0+ + ) glueball mass. The agreement of our data with the strong and weak expansion results in the corresponding limits indicates that this method can provide us with reliable information in the most interesting medium region. The trial wavefunction used in our variational method is also proven to be a good first approximation of the ground-state of the SU(3) gauge field. Upgrading this function according to correlations of adjacent plaquettes may mean better results.

The importance of the quantum recoil in the possible gamma-ray amplification by stimulated emission of radiation from positrons channelling in an acoustically excited crystal is emphasized.

We extend our work on the finite value of mean π-field in the relativistic mean field theory to the derivative coupling models for nuclear matter proposed by Zimanyi and Moszkowski. We show that a finite mean π-field may lower the energy per nucleon at a not too high density for all of those models. This qualitative result seems true in general and is model independent, although the quantitative details may be different for different models.

We compare a relativistic and thermodynamically consistent treatment for the finite-volume effect of baryons in the phase transition between hadronic matter and quark-gluon plasma, with the previous non-relativistic treatment. We find that, according to the relativistic theory, this phase transition is possible only when the baryonic spectrum is upper bounded.

Amorphous carbon films are deposited on the Mo film/ceramic substrates, which are pretreated by a laser spattering chiselling technique (2 line/mm), by using the microwave chemical vapour deposition technique. The films are characterized by x-ray diffraction, Raman spectrum, optical microscopy, and scanning electron microscopy. The experimental result indicates that the laser spattering chiselling pretreated techniques can essentially improve the field emission uniformity and the emission site density of the amorphous carbon thin film devices so that its emission site density can reach the level of actual application (undistinguishable by naked eye) from a broad well-proportioned emission area of 50 mm × 50 mm. This kind of device can show various digits and words clearly. The lowest turn-on field below 1 V/m, the emission current density over 5.0±0.1 mA/cm2, and the highest luminance 1.0×103 cd/m2 are obtained. Meanwhile, the role of the laser spattering chiselling techniques in improving the field emission properties of the amorphous carbon film are explained.

In an approximately chiral symmetric nuclear model consistent with the empirical nuclear data, we find that the medium pion mass approaches zero when the nuclear density approaches a critical value. At this critical density a chiral rotation occurs. The binding energy pernucleon jumps from about 16 MeV to 85 MeV. Since the chiral angle is not zero, we call this new state the pi-abnormal nuclear state. In this new state the pion mass becomes about 140 MeV again. Then it decreases with further increase of the nuclear density until it reaches another critical point. At this second point, the chiral angle reaches π. The pion mass starts rising. We identify this phase with the Lee–Wick's abnormal nuclear state.

Quantum electrodynamics in a laser is formulated, in which the electron-laser interaction is exactly considered, while the interaction of an electron and a single photon is considered by perturbation. The formulation is applied to the electron-laser collisions. The effect of coherence between photons in the laser is therefore fully considered in these collisions. The possibility of $\gamma-$ray laser generation by use of this kind of collision is discussed., Comment: 15 pages, 2 figures

An x-ray laser shadowgraphy experiment was conducted on Xingguang-II laser facility in 1996. A multi-layer spherical mirror was used as an imaging element and a high sensitivity CCD camera as a detector. We measured the near-field image of the Ti x-ray laser beam. With a Ti x-ray laser beam as a backlight source, we obtained a clear Cu mesh image, demonstrating the potential as advanced diagnostic measurements to study high density plasmas in inertial confinement fusion research.

With the help of a model calculation, the following features in the multiphoton detachment rate spectrum of negative ions are shown: (1) the global behavior of the rate, as a function of the photon frequency, does follow the so-called `step-like' pattern; (2) a Wigner-type cusp occurs at every threshold open for the lower photon number channel; (3) a clear dip appears at a certain frequency point slightly lower than each threshold frequency. All these features are interpreted as the general characteristics of multiphoton detachments on the R-matrix–Floquet analysis. Comparisons are made with the previous results. To the best of our knowledge, the third feature may be for the first time explained in this paper, though it is not first found by us.

We show: (1) The photoelectric effect induced by a circularly polarized light beam is exactly equivalent to a quantum transition induced by a time independent perturbation between stationary states. The equivalent energy level of the target system is then light intensity dependent. (2) This energy shift, in the dipole approximation, is similar to that of a combined Zeeman-Stark effect in magnetic and electric fields perpendicular to each other.

With the help of a model calculation based on the R-matrix - Floquet theory, the variability of multiphoton detachment rate versus laser intensity is in detail investigated. A number of interesting regularities, which can not be understood in the lowest order perturbation theory, is found out and interpreted.

We generalize the Walecka model for nuclear matter by including the π-field. It is found that a finite mean π-field may lower the energy per nucleon even in the nuclear matter of subnormal density. A mean π-field may significantly change the nuclear equation of state. The importance of considering the π-field in the relativistic mean field theory for nuclear matter is therefore emphasized.

In the present paper we derive the new generalized energy sudden approximattion theory and the generalized adiabatic nuclei theory of atom-diatomic molecule scattering through the transformation of the full Green operator. The derivation is quite simple and it is different from previous methods. The formulation has an obvious physical meaning and should lead to accurate numerical results. Numerical results for H e -H 2 scattering are given and compared with previous results.

The rapid thermal annealing temperature dependence of the recrystallization, Yb migration and its optical activation were studied for Yb-implanted silicon. For the annealing regime 800-1000-degrees-C, the Yb segregates both at the crystal/amorphous interface and at the surface, which is different from the usual segregation of Er at the crystal/amorphous interface, and the efficiency of optical activation also increases with annealing temperature. However, the amorphous layer regrows completely and no photoluminescence is observed after the annealing at 1200-degrees-C.

We show that the principle of entropy increase may be exactly founded on a few axioms valid not only for quantum and classical statistics, but also for a wide range of statistical processes., 8 pages

The influence of the relativistic finite volume effect of nucleons on the properties of dense nuclear matter is examined at finite temperature and it is found that the abnormal nuclear state can appear at sufficiently high density. Then, by using this methed the phase transition between hadronic matter and quark-gluon plasma is studied. The numerical results show that the value of nucleon radius is important for reproducing this phase transition correctly.

The potential energy surface of the H13 proton in base cytosine of the DNA molecules is calculated {\it ab initio} at the Gaussian98 MP2/6-311G(d,p) level. Two potential wells are found. One corresponds to the normal cytosine, while the other corresponds to its imino tautomer. The bindings of the proton in these wells are stable enough against the thermo-disturbance. The motions of the proton in these wells are oscillations around the nearest nitrogen atom like the pendula, and may move far away from the nitrogen atom to form the hydrogen bond with other bases. The estimated tunneling probability of the H13 proton from one well to another well shows that the life time of the proton staying in one of these wells is about 6$\times10^2$ yr. It is too long to let tautomers of cytosine be in thermodynamical equilibrium in a room temperature gas phase experiment. The biological significance of these result is discussed., 4 pages, 4 figures, replace the bmp files in figures 1 and 2 by corresponding eps files in text

I prove that not only particle motion but also wave propagation cannot be faster than light according to relativity.

A new kind of continuous variable n-mode coherent–entangled state (CV-NCES) |x2, x3, ⋅⋅⋅, xn, α〉 is proposed, which exhibits both the properties of a coherent state and an entangled state, and spans a complete and orthonormal representation. The conjugate state of CV-NCES is derived by the Fourier transformation. Moreover, a simple experimental protocol of generating a CV-NCES is proposed by using beam splitters. As applications of this CV-NCES in quantum optics, a new n-mode squeezing-Fresnel operator is constructed.

The subsolidus phase relations of a ZnO-V2O5-K2O system are investigated by X-ray powder diffraction. There is 1 ternary compound, 11 binary compounds and 14 three-phase regions in this system. The phase diagrams of V2O5-K2O with the K2O content ranging from 0 to 71 mol% and pseudo-binary system of ZnO-K2ZnV2O7 are also studied by X-ray powder diffraction and differential thermal analysis methods.

Using a linearly polarized, phase-stabilized 3-fs driving pulse of 800 nm central wavelength shape-optimized on its ascending edge by its an amplitude-reduced pulse irradiating on a superposition state of the helium atom, we demonstrate theoretically the generation of a super strong isolated 176-attosecond pulse in the spectral region of 93–124 eV. The unusually high intensity of this attosecond pulse is marked by the Rabi-like oscillations emerging in the time-dependent populations of the ground state and the continuum during the occurrence of the electron recombination, which is for the first time observed in this work.

Using a linearly polarized, phase-stabilized 2.66-femtosecond driving pulse of 400 nm central wavelength orthogonally combined with another linearly polarized long pulse of 800 nm central wavelength irradiating jointly on the helium atom, we demonstrate theoretically the generation of a clean isolated 80-attosecond pulse in the spectral region of 93–155 electron volts in a two-dimensional model.

By numerically solving time-dependent Schrdinger equation, we obtain high-order harmonic generation （HHG） spectra from the one-dimensional H atom model submitted to linear polarization bichromatic field. It is found that, appropriate bichromatic field could be a source of attosecond pulse generation since it produces a ligher line-density in harmonic generation spectra （HGS）. Based on it, we analyze the mechanism of generating denser HHG spectral lines in detail, and give density-selection numerical experiential formulas for different pulses duration, to achieve further control of the line density of HGS.