Fourth-generation signatures in D0-;D̄0 mixing and rare D decays

We study the effects of a fourth generation on D⁰-D̄⁰ mixing and the rare decays D⁰→μ⁺μ⁻, D→ℓ⁺ℓ ⁻X (where X is nonstrange), D→πℓ⁺ℓ⁻ and D→ϱγ (orωγ). D⁰-D̄⁰ mixing can be as large as the experimental limit of 0.5%. The fourth generation can enhance the branching ratios for the rare decays by several orders of magnitude: it can be as large as 10⁻⁹ for the decays D⁰→μ⁺μ⁻, D→ℓ⁺ℓ⁻X and D→πℓ⁺ℓ⁻. The long-distance contribution to the radiative decays is estimated to be ∼ 10⁻⁸ and is shown to be dominant in the three-generation model. The fourth generation can bring this branching ratio up to ∼ 10⁻⁶.     

Structure of low-lying <Superscript>12</Superscript>C resonances

The hyperspherical adiabatic expansion is combined with complex scaling and used to calculate low-lying nuclear resonances of ¹²C in the 3α model. We use Ali-Bodmer potentials and compare results for other potentials α-α with similar ⁸Be properties. A three-body potential is used to adjust the ¹²C resonance positions to desired values extending the applicability of the method to many-body systems decaying into three α-particles. For natural choices of three-body potentials we find 14 resonances below the proton separation threshold, i.e. two 0⁺, three 2⁺, two 4⁺, one of each of 1^±, 2^-, 3^±, 4^-, and 6⁺. The partial-wave decomposition of each resonance is calculated as a function of the hyperradius. Strong variation is found from small to large distance. The connection to previous experimental and theoretical results is discussed and agreements as well as disagreements are emphasized.     

HD+2，H+3和D+3与固体相互作用和三体尾流效应

从分子离子H⁺₃及其氘化同位素分子离子D⁺₃和HD⁺₂与超薄固体膜相互作用发生库仑爆炸为基础,分析讨论了H⁺₃,D⁺₃和HD⁺₂三种分子离子的形成机理,根据产物能谱分布,利用库仑爆炸技术确定了同位素分子离子HD⁺₂的结构形式,给出具体核间距数值.并确定在实验中不存在线状结构的HD⁺₂.提出一种三原子分子离子和固体相互作用中尾流效应的处理方式,通过和实验结果做比较发现这是一种非常理想的处理三体尾流效应的模式,并用之进一步确认了HD⁺₂的结构形状.文章对H⁺₃,D⁺₃和HD⁺₂三种分子离子的实验结果做了对比和讨论. 关键词： +₂')" href="#">微团簇HD⁺₂ +₃和D⁺₃')" href="#">H⁺₃和D⁺₃ 库仑爆炸 三体尾流势 团簇结构     

Time-dependent self-consistent perturbation theory and applications to molecules

The two most intense bands of the 370 nm electronic band system of tropolone have been rotationally analysed. They are separated by 18·93 cm^-1 and it has been shown that the high wavenumber band is the 0^--0^- (H₁ ¹) transition in what is almost certainly the internal hydrogen-bonding vibration v _H : the low wavenumber band is the 0⁺-0⁺ (0₀ ⁰) transition. A rotational contour analysis of both bands shows that there is an intensity alternation in K _a″ such that the ratio K _a″ even : odd is 10 : 6 in the 0⁺-0⁺ band and 6 : 10 in the 0^--0^- band. The intensity alternation, the nearly equal intensities of the 0⁺-0⁺ and 0^--0^- bands, the separation of these two bands and the anharmonic behaviour of v _H show that the separation of the 0⁺ and 0^- levels is small in the ground electronic state (probably less than 50 cm^-1) and is 18·93 cm^-1 larger in the excited electronic state.

The 0⁺-0⁺ and 0^--0^- bands are both type B showing that the electronic transition is à ¹ B ₂-X ¹ A ₁ and therefore π*-π rather than π*-n. The π*-n transition is probably shifted to high wavenumber by the internal hydrogen-bonding.     

Multiconfiguration Hartree-Fock calculations in Cr5+, Mn6+ and Fe7+

The multiconfiguration Hartree-Fock (MCHF) method is used to calculate the excitation energies and oscillator strengths, of both the length (f _L) and velocity (f _V) forms, for 1s²2s²2p⁶3s²3p⁶3d² D→1s²2s²2p⁶3s²3p⁵3d^{2 2} P ⁰,² D ⁰,² F ⁰ transitions in Cr⁵⁺, Mn⁶⁺ and Fe⁷⁺ ions of the potassium isoelectronic sequence. Comparison is made with our earlier relevant results obtained by employing the configuration interaction (CI) method which is closely related to the MCHF method. Our present investigation demonstrates that the MCHF method is more accurate than the CI method in all ions of present consideration.     

The decay processes Λ8Li → π− + 8Be1 (∼ 17 MeV)

The branching ratio is calculated for _Λ⁸Li decay to the (2⁺) ⁸Be¹ states near 17 MeV, using intermediate coupling wave functions for _Λ⁸Li and for the relevant ⁸Be¹ states. It is pointed out that this ratio is sensitive primarily to a mixing angle ? in the _Λ⁸Li wave function. Within one standard deviation, the data allow two ranges (+0.05 to +0.25 rad and +1.10 to +1.25 rad) for the value of ?. The further requirement that there also be acceptable agreement between the angular distribution expected for the subsequent ${}^8\text{Be}{}^1\text{(? 17}\text{MeV → 2}{}^4\text{He}$ decay and the data, shifts these allowed ranges for ?, to (+0.13 to 0.40) rad and (+0.9 to +1.2) rad. It is predicted that the dominant transition should be to ⁸Be¹ (16.6 MeV), as is observed to be the case, rather than to ⁸Be¹ (16.9 MeV). The interpretation of these values for ? is discussed in some detail and their implications for intermediate coupling shell-model calculations of Λ-hypernuclear wave functions are considered.     

作用表示波动方程中与面有关项

这篇短文的内容是:(i)对於量子场论中的i(δψ[σ])/(δσ(x))=V(x,σ)ψ[σ] 如何由寻常的“曲面上的薛定谔方程”导出,作一个较严格的讨论,以及 (ii)讨论上式中的V(x,σ)在什么条件下不包含有σ。我们证明了所需的条件是 (?L^I)/(?φ_μ) (?L^I)/(?φ_ν)=(?²L)/(?φ_μ?φ_ν)F(φ,φ_ρ),式中L,L^I代表总拉格朗日及作用拉格朗日,φ代表场量,φ_μ代表φ/x^μ,F(φ,φ_ρ)代表φ及φ_μ的一个任意函数。     

Optical observation of the kinetics of thermalization between the P0 and P1 excited states of Pr in symmetrical Pr-Gd pairs in CsCdBr3

The time dependence of thermalization between the ³P₀ and ³P₁ electronic states of Pr³⁺ in symmetrical Pr³⁺-Gd³⁺ pairs in CsCdBr₃, following pulsed laser excitation into either state, is reflected in the time dependence of the luminescence from both states. The ³P₀ and ³P₁ states achieve thermal equilibrium in the microsecond time domain over the temperature range of study (215-340 K). Because the ³P₀-³P₁ energy gap is larger than the phonon cutoff in CsCdBr₃, thermalization occurs via multiphonon processes. A rate-equation model for the thermalization process is presented, and the temperature dependence of the rate constants for ³P₁←³P₀ multiphonon absorption and ³P₁→³P₀ multiphonon emission is reported from 215-340 K. In contrast to CsCdBr₃, the analogous thermalization kinetics in Pr³⁺-Gd³⁺ pairs in isostructural CsMgCl₃ is not discernable in the ³P₀ and ³P₁ luminescence, because thermalization is instantaneous within the time resolution of our experiments (∼20 ns). The difference in the thermalization kinetics in the two lattices is attributed to the difference in the number of phonons required to bridge the ³P₀-³P₁ energy gap.     

Determination of the coupling constants 3Hdn, 3Hπ and 3He3Heπ from data on the differential cross sections OF n3H and n3He elastic scattering

A determination of the coupling constants ³Hdn, ³H³H_π and ³He³He_π from existing differential cross section data for n³H and n³He elastic scattering has been carried out. The method is based on the extrapolation of dσ/dΩ to the deuteron and pion poles, exploiting conformal mapping techniques. Calculations result in a value of the ³Hdn coupling constant which is ≈ 20% smaller than dispersion relation predictions. A comparison of the value obtained with predictions based on nuclear models allows one to discriminate between different potentials. The residue at the pion pole turns out to be too weak and the conclusion is drawn that it is impossible to determine the coupling constants ³H³H_π and ³He³Heπ on the basis of existing data.     

4HeH+核间距的实验测定

用MeV量级⁴HeH⁺在超薄无衬碳膜中的库仑爆炸,获得高频离子源产生⁴HeH⁺核间距的实测值为0.094±0.003nm.发现⁴HeH⁺与H⁺₂,H⁺₃不一样,其核间距大小和离子源种类及离子源参数有密切关系,并从⁴HeH⁺的形成机理与形成条件,解 关键词：     

High-resolution laser excitation spectra of linear triatomic molecules: Analysis of the B2Σ+-X2Σ+ system of SrOH and SrOD

Single-mode cw dye laser excitation spectra of the (0, 0⁰, 0)-(0, 0⁰, 0), (1, 0⁰, 0)-(1, 0⁰, 0), (0, 1¹, 0)-(0, 1¹, 0) bands of the 611- to 607-nm system of SrOH and SrOD were observed and assigned. The spectrum is consistent with a ²Σ-²Σ system where the molecule is linear in both electronic states. The rotational analysis is obtained by measuring P-R separations in the excitation spectrum. A technique which greatly aided in the spectral assignment that utilizes a monochromator as a bandpass filter in obtaining excitation spectra is described. A new spin-rotation constant, γ⁽⁺⁾ - γ^(?), was found necessary to fit the l-type doubling of the (0, 1¹, 0) mode in B²Σ⁺ of SrOH. This new constant is assumed to arise from two ${}^2\text{Σ}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ vibronic states, split by Renner-Teller interaction, of the (0, 1¹, 0) mode of A²Π. From a perturbation treatment of this electronic interaction, ?ω₂ of the (0, 1¹, 0) mode of A²Π was found to be 14 cm^?1. The linear structure of SrOH and SrOD in both electronic states is consistent with the model, in the one-electron approximation, in that the transition involves the promotion of the unpaired 5s to the 5p orbital localized on the strontium.     

Traces of Landau-Zener transitions in the fusion cross section of heavy nuclei?

Nucleus-nucleus collisions with center-of-mass energies E_c.m. close to the Coulomb barrier are investigated within the framework of time-dependent two-center shell-model states. The influence of Landau-Zener transitions on the nucleus-nucleus potential is studied in detail as a function of E_c.m. Dynamical barrier shifts and barrier fluctuations are evaluated for central collisions of ⁹⁰Zr + ⁹⁰Zr, ⁹²Zr + ⁹²Zr, ⁹⁶Zr + ⁹⁶Zr and their effect on the fusion probability is discussed explicitly. While for ⁹⁰Zr + ⁹⁰Zr no modification of the barrier penetration is found a relative enhancement (reduction) of the fusion probability up to a factor of 4 is obtained for ⁹²Zr + ⁹²Zr and⁹⁶Zr + ⁹⁶Zr.     

Cross sections for production of 43Sc, 44Sc, and 46Sc isotopes in the 45Sc + 3He reaction

Reactions ⁴⁵Sc(³He, αn)⁴³Sc, ⁴⁵Sc(³He, α)⁴⁴Sc, and ⁴⁵Sc(³He, 2p)⁴⁶Sc, resulting from the irradiation of scandium targets with a beam of ³He ions with energy from 5 to 24 MeV, are investigated in experiments on the U120M cyclotron of the Nuclear Physics Institute (Rez, Czech Republic). The activation technique is used to find the yield of the produced Sc isotopes. The induced γ activity in the targets is measured using a high-resolution HPGe detector. Despite the low binding energy of ³He and positive reaction Q values, which leads to formation of the ⁴⁴Sc and ⁴⁶Sc isotopes, the behavior of the excitation functions for the formation of these isotopes differs from the behavior of the excitation function for deuterons. Scandium-44 formation cross sections reach their maximum at the reaction Coulomb barrier. This is because not only ⁴⁴Sc but also a stable ⁴He nucleus is formed in the reaction.     

A Rhodamine Derivative Based Chemosensor with High Selectivity and Quick Respond to Cr<Superscript>3+</Superscript> in Aqueous Solution

In this paper, a new kind of colorimetric chemsensor aiming at detecting Cr³⁺ has been synthesized, and it is based on the “Off-On” effect of a rhodamine derivative. Comparing with other metal irons (Na⁺, K⁺, Ni²⁺, Hg²⁺, Fe³⁺, Mn²⁺, Co²⁺, Cd²⁺, Cu²⁺, Pb²⁺, Zn²⁺, Mg²⁺, Ba²⁺, Ag⁺, Fe²⁺, Ce³⁺), the chemsensor has a quick and accurate response to Cr³⁺ in H₂O-EtOH solution (4/1, v/v). There is an obvious change in color, from colorless to bright pink when Cr³⁺ is detected. According to the fitting curve based on Benesi-Hildebrand equation and working curve of absorption strength in UV-vis spectrum, the binding pattern of Cr³⁺ and the rhodamine derivative follows a 1:1 stoichiometry. The chemsensor shows great potential in monitoring Cr³⁺ in the aqueous medium with high efficiency, which is supposed to complete the recognition in the minimum as 5.2?×?10^?7 mol/L within 5 min.     

Charged hadron multiplicities and inclusive π− distributions in inelastic ep scattering

Electroproduction of hadrons is studied in the kinematic region W < 2.8 GeV and 0.3 < Q² < 1.4 GeV² using the DESY streamer chamber. Prong cross sections, charged-particle multiplicities and inclusive π^? distributions are presented. The average charged multiplicity is found to be independent of Q² in the Q² range studied here; however it is lower than in photoproduction. The fraction of forward π^? is found to be significantly less in electroproduction than in photoproduction. The 〈p_⊥²〉 for inclusive π^? is, for all x values, similar to that found in photoproduction.     

Hard photon corrections for Bhabha scattering

Numerical results for the α³ differential cross section for e⁺e^? → e⁺e^? are presented for the case of e⁺e^? colliding beams. Special care is given to the hard photon corrections. Acoplanarity distributions for e⁺e^? → e⁺e^?γ are also presented. Attention is drawn to experimental conditions which require the calculation of still higher order corrections.     

Symmetry and boundness of four-particle coulomb systems

The problem of boundness of a ⁺ b ⁺ c ⁻ d ⁻ four-particle Coulomb systems (quadrions) is studied versus the masses of the particles involved. Inequalities that make it possible to deduce that, if some reference quadrions form a bound state, the same is true for a large number of quadrions formed by particles having various masses were derived. A compendium of calculations for energies of reference systems that possess various symmetries [positronium molecules (e ⁺ e ⁺ e ⁻ e ⁻) and quadrions of the a ⁺ b ⁺ b ⁻ b ⁻, a ⁺ b ⁺ a ⁻ b ⁻, and a ⁺ a ⁺ b ⁻ c ⁻ types] is given, and groups of bound asymmetric quadrions corresponding to them are determined. An inequality for kinetic energies of particles that makes it possible to find out, by using asymmetric reference systems, whether specific quadrions are bound is obtained. It is shown that the boundness of many quadrions is ensured by the boundness of respective three-particle systems. The entire body of the present results permits proving that, of the total number of 406 quadrions containing electrons, muons, pions, kaons, protons, deuterons, and tritons and their antiparticles, 227 quadrions are bound.     

Magnetic field effects on electron transfer reactions involving sextet-spin (S = 5/2) intermediates generated on photoexcitation of a Cr(III)-porphyrin complex

The excited trip-sextet (⁶T₁) state of chloro-(3-methylimidazol)-(meso-tetraphenylporphyrinato) chromium(III) (Cr^IIIP) is quenched by 1,1′-dibenzyl-4,4′-bipyridinium (BV²⁺) in acetonitrile through electron transfer to give ⁵(Cr^IIIP^·+) and ²BV^·+. The intermediate is a geminate ion pair in the sextet (Sx) state ⁶[⁵(Cr^IIIP^·+) ²BV^·+], which decays through either the escape from a solvent cage to give the free ions or the spin conversion to the quartet (Qa) state followed by back electron transfer. The free ion yield (Φ_FI) increased with increasing magnetic field from 0 to 4 T and then slightly decreased from 4 T to 10 T. These magnetic field effects are explained as follows. Under low fields where the Zeeman splitting of the spin sublevels is lower than or comparable with the electron spin dipole—dipole interaction within ⁵(Cr^IIIP^·+), this interaction effectively induces the Sx → Qa conversion of [⁵(Cr^IIIP^·+)²BV⁺] to result in low Φ_FI values. Under high fields where the Zeeman splitting is larger than the dipole—dipole interaction, the Sx → Qa conversion is decreased with increasing field to cause higher Φ_FI values. The slight decrease in Φ_FI above 4 T may be due to the Δg mechanism.     

Eu2+,Mn2+在BaZnP2O7中的发光及Eu2+→Mn2+能量传递

采用高温固相法合成了BaZnP₂O₇:Eu²⁺,Mn²⁺荧光粉,并对其发光性质及Eu²⁺对Mn²⁺的能量传递机理进行了研究.Eu²⁺和Mn²⁺在380 nm和670nm的发射峰分别由Eu²⁺的5d—4f跃迁和Mn²⁺的⁴T₁(^{4关键词： 磷酸盐 2+}')" href="#">Eu²⁺ 2+')" href="#">Mn²⁺ 能量传递