共查询到20条相似文献,搜索用时 31 毫秒
1.
G. Burgun P. Bertranet E. Lesquoy A. Muller E. Pauli S. Zylberajch F. James L. Montanet E. Paul P. Saetre D.M. Sendall 《Physics letters. [Part B]》1973,46(3):481-485
From a study of 70 000 K° decays in the CERN 2m hydrogen bubble chamber, we have estimated the rate for KS0 → π+π?γ for different cuts in the γ momentum. The results are in good agreement with inner bremsstrahlung on KS0 → π+π?. For γ momentum in the K° c.m. greater than 50 MeV/c, we obtain the branching ratio: Γ(KS → π+π?γ, k>50 MeV/c)/Γ(KS→π+π?)=(2.8. ± 0.6)×10?3. This leads to an estimate for the direct γ emission process: Γ(KS→π+π?γ direct)/Γ(KS → π+π?)=(0.3 ± 0.6) × 10?3. 相似文献
2.
A.V. Syromyatnikov 《Journal of magnetism and magnetic materials》2009,321(7):928-930
We discuss the spin-wave interaction in two-dimensional (2D) Heisenberg ferromagnet (FM) with dipolar forces at TC?T?0 using 1/S expansion. A comprehensive analysis is carried out of the first 1/S corrections to the spin-wave spectrum. In particular, we obtain that the spin-wave interaction leads to the gap in the spectrum εk renormalizing greatly the bare gapless spectrum at small momenta k. Expressions for the spin-wave damping Γk are derived self-consistently and it is concluded that magnons are well-defined quasi-particles in both quantum and classical 2D FMs at small T. We observe thermal enhancement of both Γk and Γk/εk at small momenta. In particular, a peak appears in Γk and Γk/εk at small k and at any given direction of k. If S∼1 the height of the peak in Γk/εk is not larger than a value proportional to T/D?1, where D is the spin-wave stiffness. In the case of large spins S?1 the peak in Γk/εk cannot be greater than that of the classical 2D FM found at k=0 whose height is small only numerically: Γ0/ε0≈0.16 for the simple square lattice. 相似文献
3.
We demonstrate a technique for directly measuring the quadratic Zeeman shift using stimulated Raman transitions. The quadratic Zeeman shift has been measured yielding Δν=1296.8±3.3 Hz/G2 for magnetically insensitive sublevels (5S1/2,F=2,mF=0→5S1/2,F=3,mF=0) of 85Rb by compensating the magnetic field and cancelling the ac Stark shift. We also measured the cancellation ratio of the differential ac Stark shift due to the imbalanced Raman beams by using two pairs of Raman beams (σ+, σ+) and it is 1:3.67 when the one-photon detuning is 1.5 GHz in the experiment. 相似文献
4.
Hari Prakash 《Optik》2011,122(12):1058-1060
Recently Ahmad et al. [Optik 2009;120;68; Optics Commun. 2007;271:162; Chin. Phys. Lett. 2006;23:2438] have studied non-classical properties of superposition of two-coherent states of the form, |ψ〉=K[|α〉+eiξ|αei?〉] for the special cases with values ? = π/2, 3π/2, and π, and for arbitrarily fixed values of ξ. We point out that some of their results are special cases of our recently published work [Physica A 319, 305 (2003); Physica A 341, 201(2004)] on the most general superposition of two arbitrary coherent states of the form ∼(Z1|α〉+Z2|β〉), where X1,2, α and β are arbitrary and only restriction on these is the normalization condition for the superposed state. To make our point we first obtain results for (i) squeezing of the most general Hermitian operator Xθ = X1 cos θ + X2 sin θ, with X1 + iX2 = a, is the annihilation operator, and (ii) sub-Poissonian photon statistics, for the superposed state |ψ〉 with a general ? and, then obtain results of Ahmad et al. for ? = π/2, 3π/2, and π and for θ = 0 and π/2. It is interesting to note that the arbitrarily fixed values ξ = |α|2 and −|α|2 for ? = π/2 and 3π/2, respectively by Ahmad et al. are the values at which we get maximum squeezing working in a rigorous way. 相似文献
5.
Geol Moon 《Optics Communications》2008,281(2):294-298
We have studied the nonstationary effects in saturated absorption spectroscopy of the 87Rb D2 line. Varying the size of the σ+ polarized pump laser beam, we observed saturated absorption spectra for the σ± polarized probe beam. For equal polarizations of the pump and probe beams, we found that the resonance signal for the Fg = 1 → Fe = 2 line, and the crossover lines between Fg = 1 → Fe = 2 and Fg = 1 → Fe = 1 (and 0) lines increased to a greater extent than the others. This observation can be understood from the calculated time evolution of the populations of the ground-state sublevels by means of a rate equation model. We also compared experimental data for other conditions with the calculated results. We found good agreement between the calculated results and the data. 相似文献
6.
V.B. Tiwari S. Singh S.R. Mishra H.S. Rawat S.C. Mehendale 《Optics Communications》2006,263(2):249-255
7.
We study a generalized Hubbard model on the two-leg ladder at zero temperature, focusing on a parameter region with staggered flux (SF)/d-density wave (DDW) order. To guide our numerical calculations, we first investigate the location of a SF/DDW phase in the phase diagram of the half-filled weakly interacting ladder using a perturbative renormalization group (RG) and bosonization approach. For hole doping δ away from half-filling, finite-system density-matrix renormalization-group (DMRG) calculations are used to study ladders with up to 200 rungs for intermediate-strength interactions. In the doped SF/DDW phase, the staggered rung current and the rung electron density both show periodic spatial oscillations, with characteristic wavelengths 2/δ and 1/δ, respectively, corresponding to ordering wavevectors 2kF and 4kF for the currents and densities, where 2kF = π (1 − δ). The density minima are located at the anti-phase domain walls of the staggered current. For sufficiently large dopings, SF/DDW order is suppressed. The rung density modulation also exists in neighboring phases where currents decay exponentially. We show that most of the DMRG results can be qualitatively understood from weak-coupling RG/bosonization arguments. However, while these arguments seem to suggest a crossover from non-decaying correlations to power-law decay at a length scale of order 1/δ, the DMRG results are consistent with a true long-range order scenario for the currents and densities. 相似文献
8.
Fast heating of target material by femtosecond laser pulse (fsLP) with duration τL∼40-100 fs results in the formation of thermomechanically stressed state. Its unloading may cause frontal cavitation of subsurface layer at a depth of 50 nm for Al and 100 nm for Au. The compression wave propagating deep into material hits the rear-side of the target with the formation of rarefaction wave. The last may produce cracks and rear-side spallation. Results of MD simulations of ablation and spallation of Al and Au metals under action fsLP are presented. It is shown that the used EAM potentials (Mishin et al. and our new one) predict the different ablation and spallation thresholds on absorbed fluence in Al: ablation Fa=60{65} mJ/cm2and spallation Fs=120{190} mJ/cm2, where numbers in brackets { } show the corresponding values for Mishin potential. The strain rate in spallation zone was 4.3×109 1/s at spallation threshold. Simulated spall strength of Al is 7.4{8.7} GPa, that is noticeably less than 10.3{14} GPa obtained from acoustic approximation with the use of velocity pullback on velocity profile of free rear surface. The ablation threshold Fa≈120 mJ/cm2 and crater depth of 110 nm are obtained in MD simulations of gold with the new EAM potential. They agree well with experiment. 相似文献
9.
The electrical property of a KTiOPO4 single crystal was studied by means of a dielectric spectroscopy method in the temperature range from −100 to 100 °C. Dielectric dispersion began at a temperature, TS=−80 °C. It is believed that this dielectric dispersion is related to the ionic hopping conduction, which arises mainly from the jumping of K+ ions. The activation energy concerned with hopping conduction is Ea∼0.20 eV above TS. TS=−80 °C can be the minimum temperature for the hopping K+ ion. 相似文献
10.
Zhonghua Ou Lei LuXiaofei Zhu Guanghao ZhengJianfeng Li Yong LiuHuimin Yue Zhiyong DaiLixun Zhang 《Optik》2014
Based on the coupled mode equations and elastic optic effect theory, the relationship between polarization maintaining fiber (PMF) beat length and external pressure was analyzed. Moreover, the beat length variation with different external pressure values F as well as angles θ between the pressure direction and PMF's x-axis was calculated numerically. The results demonstrated that the beat length variation was determined both by F and θ simultaneously. When F was a constant, the beat length was changed periodically in π cycle sinusoidal form with θ variation. Then, the minimum and maximum values of beat length would be obtained when θ were even and odd multiples of π/2, respectively. Meanwhile, the beat length variation was linear with F as θ was fixed. In this situation and with F increasing, if θ ∈ (kπ + π/4, kπ + 3π/4) (k ∈ Z), the beat length would increase linearly; otherwise, the beat length variation would be in the opposite direction while θ ∈ (kπ − π/4, kπ + π/4) (k ∈ Z); however, it remained almost unchanged in the case of θ = kπ ± π/4 (k ∈ Z). Finally, the beat length was measured with different pressure values F and angles θ based on a Sagnac interferometer system, and the results shown a great agreement with the theoretical analysis and simulation. 相似文献
11.
K. Sambasiva Rao P. Murali Krishna D. Madhava Prasad Joon Hyung Lee 《Journal of Physics and Chemistry of Solids》2009,70(9):1231-677
Tungsten bronze (TB)-type oxide ceramic Pb0.74K0.13Y0.13Nb2O6 (PKYN) has been synthesized by the standard solid state reaction method. Single phase formation, orthorhombic crystal structure was confirmed by X-ray diffraction (XRD). The substitution of Y3+ in Pb0.74K0.52Nb2O6 (PKN) decreased the unit cell volume and TC=260 °C. PKYN exhibited the remnant polarization, Pr=8.5 μC/cm2, and coercive field, Ec=28.71 kV/cm. Electrical spectroscopy studies were carried out over the temperature (35-595 °C) and frequency (45 Hz-5 MHz) ranges, and the charge carrier phenomenon, grain-grain boundary contribution and non-Debye-type relaxation were analyzed. The relaxation species are immobile charges in low temperature and oxygen vacancies at higher temperature. The theoretical values computed using the relations, ε′=ε∞+sin(n(T)π/2)(a(T)/ε0)(ωn(T)−1); σ(ω)=σdc+Aωn are fitted with the experimental one. The n and A parameters suggested that the charge carrier's couple with the soft mode and become mobile at TC. The activation enthalpy, Hm=0.38 eV, has been estimated from the hopping frequency relation ωp=ωe exp(−Hm/kBT). The piezoelectric constants Kt=35.4%, d33=69×10−12 C/N, d31=−32×10−3 mV/N, S11E=17.8 pm2/N, etc., achieved in PKYN indicate the material is interesting for transducer applications. The activation energies from different formalisms confirmed the ionic-type conduction. 相似文献
12.
Ali Rostamnejadi Hadi Salamati Parviz Kameli Hossein Ahmadvand 《Journal of magnetism and magnetic materials》2009,321(19):3126-3131
Magnetic nanoparticles of La0.67Sr0.33MnO3 (LSMO) manganite were prepared by sol-gel method. Phase formation and crystal structure of the synthesized powder were examined by the X-ray diffraction (XRD) using the Rietveld analysis. The mean particle size was determined by the transmission electron microscopy (TEM). Infrared transmission spectroscopy revealed that stretching and bending modes are influenced by calcinations temperature. The temperature dependence of the ac magnetic susceptibility was measured at different frequencies and ac magnetic fields in the selected ranges of 40-1000 Hz and 80-800 A/m, respectively. The temperature dependence of ac susceptibility shows a characteristic maxima corresponding to the blocking temperature near room temperature. The frequency dependence of the blocking temperature is well described by the Vogel-Fulcher law. By fitting the experimental data with this law, the relaxation time τ0=1.7×10−12 s, characteristic temperature T0=262±3 K, anisotropy energy Ea/k=684±15 K and effective magnetic anisotropy constant keff=2.25×104 erg/cm3 have been obtained. dc Magnetization measurement versus magnetic field shows that some of LSMO nanoparticles are blocked at 293 K. The role of magnetic interparticle interactions on the magnetic behavior is also investigated. 相似文献
13.
A. Martinelli M. Ferretti A. Palenzona M. Merlini 《Physica C: Superconductivity and its Applications》2009,469(13):782-784
The crystal structure of SmFeAs(O0.93F0.07) has been investigated under high pressure (up to ∼9 GPa) by means of synchrotron powder diffraction analysis followed by Rietveld refinement. The bulk modulus was calculated (K0 = 103 GPa) using a 3rd order Birch–Murnaghan equation of state and resulted in quite good agreement with theoretical calculations reported for LaFeAsO. The linear compressibilities βa and βc are 2.11(4) and 4.56(7) × 10−3 GPa−1, respectively. 相似文献
14.
The cross sections of inelastic electron scattering are measured near the threshold of single-pion production by a proton at k2=2.5, 3.5, 5.0 and 8.0 fm? in the polarization range of the virtual photon ?=0.3–0.9. The separation of the |E0+|2 and k2|S0+|2 contributions to the cross-section slope at threshold is carried out and thus a new method of determining the FA and Fπ form factors is realized. The values for the axial mass and mean-square radius of the pion are obtained. 相似文献
15.
We present experimental results involving controlled configuration mixing in two-photon spectroscopy of highly-excited states by exploiting a weak external electric field and collisions. The method has allowed new extensions to high members of the two-photon forbidden J = 3 odd-parity 5snf 1F3 and the J = 0, even-parity 5sns 1S0 Rydberg series of neutral strontium to be observed. We achieve resonant two-photon transverse excitation of a high density atomic jet by using a narrow bandwidth tunable dye laser in a heat pipe setup with sensitive ionization detection. Experimental term values are extended for the 5sns 1S0 series up to n = 46. By suitable exploitation of the composition and pressure of the buffer gases in conjunction with the electric field strength in the excitation region and the exciting laser beam intensity we have also extended observations up to n = 44 for the 5snf 1F3 series and up to n = 46 for the 5snp 1P1 series. Our results demonstrate a novel and remarkably simple experimental method to access high Rydberg states to which transitions are forbidden from the ground state by parity and other selection rules. 相似文献
16.
J.G. Philis 《Journal of Molecular Spectroscopy》2005,232(1):26-29
Resonance-enhanced multiphoton ionization (REMPI) has been applied to study the n → 3p Rydberg transition of pyrimidine (jet-cooled sample and mass resolved spectrum). Only the one component, the 3pz(B2), appears in the (2 + 1) REMPI and the active vibrations are ν6a = 622, ν1 = 946, and ν9a = 1116 cm−1. The symmetry of the state was determined by polarization measurements (linear, circular polarization). The first (π∗,n) 3B1 triplet state appears as a one-photon resonance in the three-photon ionization process. 相似文献
17.
The high resolution infrared spectra of monoisotopic F35Cl18O3 and F37Cl18O3 have been studied in the region of the ν4 fundamentals, centered at 1278.3 and 1263.3 cm−1, respectively. Large perturbations are observed in both bands due to a Fermi type anharmonic resonance with the ν2 + ν5 combination bands, centered at 1270.7 cm−1 in F35Cl18O3 and 1257.3 cm−1 in F37Cl18O3. In particular, they affect the kl > 0 levels of the v4 = 1 and v2 = v5 = 1 states which cross at kl ? 18 in F35Cl18O3 and kl ? 3 in F37Cl18O3, due to the opposite values of and . The Δl = Δk = ±2 and Δl = 0, Δk = ±3 essential resonances are also effective in the excited states of the dyad in F35Cl18O3, while in F37Cl18O3 only the Δl = Δk = ±2 one is active. In the spectrum of F35Cl18O3 3423 transitions have been assigned, 10% of them belonging to ν2 + ν5. The rovibrational parameters and the interaction constants between the v4 = 1 and v2 = v5 = 1 levels have been obtained. The depertubed band origins of ν4 and ν2 + ν5 are 1277.310567(165) and 1271.753733(195) cm−1, respectively, and the anharmonic resonance constant is 2.804416(153) cm−1. For F37Cl18O3, 3022 transitions have been assigned, 38% belonging to the ν2 + ν5 combination band. The depertubed band origins are 1260.856338(123) and 1259.872338(134) cm−1, for ν4and ν2 + ν5 and the constant is 2.9350669(405) cm−1. The equilibrium geometry of perchloryl fluoride, re (ClO) = 139.7(3) pm, re (ClF) = 161.0(5) pm, and αe (OClO) = 115.7(4) degree, has been determined using the Ae and Be equilibrium constants of the four symmetric isotopologues of perchloryl fluoride, F35/37Cl16O3 and F35/37Cl18O3. 相似文献
18.
A.A. Kartamyshev E.P. Krasnoperov Yu.D. Kuroedov N.A. Nizhelskiy O.L. Poluschenko 《Physica C: Superconductivity and its Applications》2009,469(14):805-809
A magnetic filed relaxation at the center of a pulse-magnetized single-domain Y–Ba–Cu–O superconductor at 78 K has been studied. In case of a weak magnetization, the magnetic flux density increases logarithmically and normalized relaxation rate defined as S = −d(lnB)/d(lnt) is negative (S = −0.037). When an external magnetic field magnitude increases, the relaxation rate first decreases in absolute value, then changes sign (becomes positive, S > 0) and after reaching some maximum finally reduces to a very small value. Non-monotonous dependence of S vs. Ha is explained by a non-homogeneous local temperature distribution during a pulse magnetization. 相似文献
19.
The pure rotational spectrum of the molecular ion TiF+ in its 3Φr ground state has been measured in the range 327-542 GHz using millimeter-wave direct absorption techniques combined with velocity modulation spectroscopy. TiF+ was made in an AC discharge from a mixture of TiCl4, F2 in He, and argon. Ten transitions of this ion were recorded. In every transition, fluorine hyperfine interactions, as well as the fine structure splittings, were resolved. The fine structure pattern was found to be regular with almost equal spacing in frequency between the three spin components, in contrast to TiCl+, which is perturbed in the ground state. The data were fit with a case (a) Hamiltonian and rotational, fine structure, and hyperfine constants were determined. The bond length established for TiF+, r0 = 1.7775 Å, was found to be shorter than that of TiF, r0 = 1.8342 Å—also established from mm-wave data. The hyperfine parameters determined are consistent with a δ1π1 electron configuration with the electrons primarily located on the titanium nucleus. The nuclear spin-orbit constant a indicates that the unpaired electrons are closer to the fluorine nucleus in TiF+ relative to TiF, as expected with the decrease in bond length for the ion. The shorter bond distance is thought to arise from increased charge on the titanium nucleus as a result of a Ti2+F− configuration. A similar decrease in bond length was found for TiCl+ relative to TiCl. 相似文献
20.
Keitaro Tezuka Yue Jin Shan Kenji Ohoyama 《Journal of Physics and Chemistry of Solids》2007,68(11):2133-2137
Chromium(II) sulfide, Y2CrS4, prepared by a solid-state reaction of Y2S3 and CrS, showed an antiferromagnetic transition at 65 K. The neutron diffraction patterns at 10 and 90 K were both well refined with the space group Pca21. At 90 K, cell parameters were a=12.5518(13) Å, b=7.5245(8) Å, and c=12.4918(13) Å. At 10 K, magnetic peaks were observed, which could be indexed on the same unit cell. Magnetic moments of chromium ions were parallel to the b-axis and antiferromagnetically ordered in each set of the 4a sites. 相似文献