Ab initio calculation of the ground and first excited states of the lithium dimer

Based on a high level ab initio calculation which is carried out with the multireference configuration interaction method under the aug-cc-pVXZ (AVXZ) basis sets, X=T, Q, 5, the accurate potential energy curves (PECs) of the ground state ${\rm{X}}{}^{{\rm{1}}}{\rm{\Sigma }}_{g}^{+}$ and the first excited state ${\rm{A}}{}^{{\rm{1}}}{\rm{\Sigma }}_{u}^{+}$ of Li₂ are constructed. By fitting the ab initio potential energy points with the Murrell–Sorbie potential function, the analytic potential energy functions (APEFs) are obtained. The molecular bond length at the equilibrium (R_e), the potential well depth (D_e), and the spectroscopic constants (B_e, ω_e, α_e, and ω_eχ_e) for the ${\rm{X}}{}^{{\rm{1}}}{\rm{\Sigma }}_{g}^{+}$ state and the ${\rm{A}}{}^{{\rm{1}}}{\rm{\Sigma }}_{u}^{+}$ state are deduced from the APEFs. The vibrational energy levels of the two electronic states are obtained by solving the time-independent Schrödinger equation with the Fourier grid Hamiltonian method. All the spectroscopic constants and the vibrational levels agree well with the experimental results. The Franck–Condon factors (FCFs) corresponding to the transitions from the vibrational level (v′=0) of the ground state to the vibrational levels (v″=0–74) of the first excited state have been calculated. The FCF for the vibronic transition of ${\rm{A}}{}^{{\rm{1}}}{\rm{\Sigma }}_{u}^{+}$(v″=0) ←${\rm{X}}{}^{{\rm{1}}}{\rm{\Sigma }}_{g}^{+}$(v′=0) is the strongest. These PECs and corresponding spectroscopic constants provide reliable theoretical references to both the spectroscopic and the molecular dynamic studies of the Li₂ dimer.     

Possible tests of neutrino maximal mixing and comments on matter effects

We show in a simple and general way that matter effects do not contribute to the average value of the transition probabilities of solar ν_e's into other states in the case of maximal mixing of any number of massive neutrinos. We also show that future solar neutrino experiments (Super-Kamiokande and SNO) will allow to test the model with maximal mixing of three massive neutrinos in a way that does not depend on the initial solar neutrino flux.     

Cross section of the charged current reaction C(ve, e)Ng.s.

The charged current nuclear transition ¹²C(v_e, e⁻)¹²N_g.s. has been observed in the KARMEN experiment. The flux average cross section for v_e from μ⁺ decay at rest is determined to be σ = [8.1±0.9(stat.)±0.75 (syst.)]×10⁻⁴²cm². For the first time also the energy dependence of the cross section has been measured for neutrino energies up to 50 MeV.     

Reconciling cold dark matter with COBE/IRAS plus solar and atmospheric neutrino data

We present a model where an unstable MeV Majorana tau neutrino can naturally reconcile the cold dark matter model (CDM) with cosmological observations of large and small scale density fluctuations and, simultaneously, with data on solar and atmospheric neutrinos. The solar neutrino deficit is explained through long wavelength, so-called just-so oscillations involving conversions of ν_e into both ν_μ and a sterile species ν_s , while atmospheric neutrino data are explained through ν_μ to ν_e conversions. Future long baseline neutrino oscillation experiments, as well as some reactor experiments will test this hypothesis. The model is based on the spontaneous violation of a global lepton number symmetry at the weak scale. This symmetry plays a key role in generating the cosmologically required decay of the ν_τ with lifetime τ_ντ ≈ 10²-10⁴ seconds, as well as the masses and oscillations of the three light neutrinos ν_e, ν_μ and ν_s required in order to account for solar and atmospheric neutrino data. It also leads to the invisibly decaying Higgs signature that can be searched at LEP and future particle colliders.     

A new measurement of the Li(d,p)Li cross section and consequences for Be(p,γ)B

A novel scheme for measuring the cross section of the ⁷Be(p,γ)⁸B reaction, the major source of high energy neutrinos from the sun, is presented. The scheme involves a strictly uniform particle beam and overcomes some of the recognized experimental uncertainties of previous measurements. A new measurement of σ[⁷Li(d,p)⁸Li] has been carried out using this setup, and the present value of σ[⁷Li(d,p)⁸Li] = 155(8) mb at the top of the E_d(lab.) = 776 keV resonance is compared with previous measurements. A new issue regarding both the (d,p) and (p,γ) reactions has been examined: reaction-product nuclei which are backscattered out of the target. Measurements and simulations carried out in the course of this investigation are presented and discussed in the context of possible effects on the measured cross sections of these reactions.     

NFX(X=-1,0,+1)分子离子基态的结构与势能函数

用密度泛函理论的B3LYP方法,分别以6-311++g(df,3pd),6-311g(3d,3p)和6-311++g(3df,3pd)为基函数对NF分子、NF⁺和NF^-离子基态进行几何优化和频率计算,并进行单点能扫描计算.用最小二乘法拟合得到NF^X(X=-1,0,+1)分子离子基态的Murrell-Sorbie势能函数.利用得到的解析势能函数计算出的NF分子和NF⁺离子基态光谱常数(B_e,α_e,ω_e,ω_eχ_e)与实验值符合很好.首次得到NF^-离子基态的光谱常数(B_e,α_e,ω_e,ω_eχ_e)和力常数(f₂,f₃,f₄),为NF-离子基态的后期研究提供理论参考.     

Atmospheric neutrinos: LMA oscillations, Ue3 induced interference and CP-violation

We consider oscillations of the low energy (sub-GeV sample) atmospheric neutrinos in the three neutrino context. We present the semi-analytic study of the neutrino evolution and calculate characteristics of the e-like events (total number, energy spectra and zenith angle distributions) in the presence of oscillations. At low energies there are three different contributions to the number of events: the LMA contribution (from ν_e-oscillations driven by the solar oscillation parameters), the U_e3-contribution proportional to s₁₃², and the U_e3-induced interference of the two amplitudes driven by the solar oscillation parameters. The interference term is sensitive to the CP-violation phase. We describe in details properties of these contributions. We find that the LMA, the interference and U_e3 contributions can reach 5–6%, 2–3% and 1–2% correspondingly. An existence of the significant (>3–5%) excess of the e-like events in the sub-GeV sample and the absence of the excess in the multi-GeV range testifies for deviation of the 2–3 mixing from maximum. We consider a possibility to measure the deviation as well as the CP-violation phase in future atmospheric neutrino studies.     

COULD 7Be BE DESTROYED BY NEUTRON ABSORPTION IN THE SUN? -A NOTE ON THE SOLAR NEUTRINO PUZZLE

A comparison is made between the rate of the ⁷Be(p,y) ⁸B reaction and the rate of the neutron absorption reaction ⁷Be(n,p) ⁷Li which might have been important in. destroying ⁷Be in the solar interior.     

Measurements of interaction cross sections and radii of He isotopes

Secondary beams of ³He, ⁴He, ⁶He, and ⁸He were produced through the projectile fragmentation of an 800 MeV/nucleon ¹¹B primary beam. Interaction cross sections (σ_I) of all He isotopes of 790 MeV/nucleon on Be, C, and Al targets were measured by a transmission-type experiment. The interaction nuclear radii of He isotopes R_I(He) = (σ_I/π)^1/2 − R _I(T) where R_I(T) is the radius of the target nucleus, have been deduced to be R_I(³He) = 1.59 ± 0.06 fm, R_I(⁴He) = 1.40 ± 0.05 fm, R_I(⁶He) = 2.21 ± 0.06 fm, and R_I(⁸He) = 2.52 ± 0.06 fm.     

Minimal SUSY SO(10), b–τ unification and large neutrino mixings

We show that the assumption of type II seesaw mechanism for small neutrino masses coupled with b–τ mass unification in a minimal SUSY SO(10) model leads not only to a natural understanding of large atmospheric mixing angle (θ₂₃) among neutrinos, as recently noted, but also to large solar angle (θ₁₂) and a small θ₁₃≡U_e3 as required to fit observations. No additional symmetries are required to obtain large neutrino mixings. The proposed long baseline neutrino experiments will provide a crucial test of this model since it predicts U_e30.16.     

A hybrid mode of one- and two-surface multipactor on grooved dielectric surface

A hybrid mode of one- and two-surface multipactor on the grooved dielectric surface is studied in detail using both an analytical approach and two-dimensional particle-in-cell(2D PIC) simulations. When the groove width L eE_0/(4πm_ef~2),there are one-surface multipactor and one-order two-surface multipactor on the grooved dielectric surface, and only one slope of the groove has the multipactor anytime. When L eE0/(4πme f~2), both slopes may have the multipactors. The electron surface density of the multipactor discharge has a sharp increase at the length L = eE_0/(4πm_ef~2).     

Effects of collision energy and rotational quantum number on stereodynamics of the reactions:H(~2S)+NH(v=0,j=0,2,5,10)→N(~4S)+H_2

The stereodynamical properties of H(~2S) + NH(v = 0,j = 0,2,5,10)→N(~4S) + H_2 reactions are studied in this paper by using the quasi-classical trajectory(QCT) method with different collision energies on the double many-body expansion(DMBE) potential energy surface(PES)(Poveda L A and Varandas A J C 2005 Phys.Chem.Chem.Phys.7 2867).In a range of collision energy from 2 to 20 kcal/mol,the vibrational rotational quantum numbers of the NH molecules are specifically investigated on v = 0 and j = 0,2,5,10 respectively.The distributions of P(θ_r),P(φ_r),P(θ_r,φ_r),(2π/σ)(dσ_(00)/dω_t)differential cross-section(DCSs) and integral cross-sections(ICSs) are calculated.The ICSs,computed for collision energies from 2 kcal/mol to 20 kcal/mol,for the ground state are in good agreement with the cited data.The results show that the reagent rotational quantum number and initial collision energy both have a significant effect on the distributions of the k-j',the k-k'-j',and the k-k' correlations.In addition,the DCS is found to be susceptible to collision energy,but it is not significantly affected by the rotational excitation of reagent.     

Measurement of pionic and muonic X-rays IN B

The energies of muonic 2p-1s X-rays in ¹⁰B and ¹¹B have been measured to be 52217(8) eV and 52279(5) eV, from which the rms nuclear charge radii were calculated to be 2.44(6) fm and 2.38(4) fm. The energies and widths of pionic 2p-1s X-rays have been measured in ¹⁰B to be 65901(13) eV and 1780(30) eV, and in ¹¹B to be 65120(26) and 1720(80) eV. The sensitivity of the strong interaction shift to the neutron matter distributions has been investigated using an optical-model approach. The results of these calculations are not in good agreement with the experimental results when reasonable values of the nuclear matter distributions are used.     

基于ab initio的BD~+离子激光冷却理论研究

基于相关一致基组aug-cc-pV5Z,采用内收缩多参考组态相互作用方法计算了BD~+离子两个最低解离极限B~+(~1Sg)+D(~2Sg)和B+(~3Pu)+D(~2Sg)对应的5个Λ—S态(X~2Σ~+,A~2Π,B~2Σ+,a~4Π和b~4Σ~+)的势能曲线和跃迁偶极矩.根据计算结果,求解核运动的径向薛定谔方程得到相应电子态的振-转光谱常数、Franck-Condon(F-C)因子和振动能级辐射寿命.其中A~2Π—X~2Σ~+的F-C因子(f_(00)=0.923)、辐射寿命(τ=235 ns)满足激光直接冷却的条件.因此,我们基于分子转动跃迁提出了一个可实现Doppler激光冷却的光循环方案:A~2Π_(1/2)(υ′=0)—X~2Σ+(υ′′=0,1),其中υ′=0中包含2个转动能级,υ′′=0和υ′′=1中分别包含6个和4个转动能级.根据方案,模拟了激光冷却过程中的分子布居数动力学变化过程,并计算了初速度为100 m/s的BD~+,历经5.4 ms散射1150个光子可减速到4.6 m/s、温度为13 mK.     

Stray-field imaging of quadrupolar nuclei of half integer spin in solids

A report is presented on the observation of Hahn echoes from the following quadrupolar nuclei of half integer spin (I) in polycrystalline solids in the large static magnetic field gradient (37.5 T/m) which exists in the fringe field of a superconducting solenoid: ⁷Li, ²³Na, ¹¹B, ⁶⁵Cu (I = 3/2); ²⁷Al (I = 5/2); ⁵¹V, ⁵⁹Co (I = 7/2); and ¹¹⁵In (I = 9/2). ²³Na echo-trains from NaCl (with non-selective excitation) and from Na₂SO₄ (with selective excitation) are compared quantitatively for two different RF pulse sequences: 90_x-(τ-90_y-τ-echo-)_n and 90_x-(τ-90_x-τ-echo-)_n. The signals obtained from RF pulses corresponding to non-selective 90 ° pulses were shown to be quantitative, whereas in the selective case smaller signals were obtained since only the central transition contributed. The loss of signal from this cause can be distinguished from small signals resulting from low density of nuclei by use of the second sequence. A ⁷Li image obtained from LiF in a cylindrical glass-vial is shown.     

Are there sterile neutrinos in the flux of solar neutrinos on the earth?

It is shown that the future SNO and Super-Kamiokande experiments, in which high energy⁸B neutrinos will be detected through the observation of CC, NC and –e elastic scattering processes, could allow to reveal in a model independent way the presence of sterile neutrinos in the flux of solar neutrinos on the earth. Lower bounds for different averaged values of the probability of transition of solar v^e'S into sterile states and for the total flux of⁸B neutrinos are derived in terms of measurable quantities. The possibilities to reveal the presence of v and/or v in the solar neutrino flux on the earth are also considered and the case of transitions of solar v^e'S only into sterile states is discussed. Some numerical results for a simple model with v–v^s mixing are given.     

Cyclotron resonance and effective mass renormalizations in Sr2RuO4

Using a microwave cavity perturbation technique, we have succeeded in observing cyclotron resonances in the layered Perovskite superconductor Sr₂RuO₄. Three cyclotron masses are deduced, corresponding to m_cγ=9.7m_e, m_cβ=5.8m_e and m_c=4.3 m_e. A comparison between these values and the effective masses deduced from other techniques provides us with a unique means of gauging the role of Coulomb correlations in the title compound.     

OSCILLATIONS DRIVEN BY 3He IN THE NUCLEAR REACTIONSYSTEM DISTURBED BY CONVECTIVE MOTION

The nuclear reactions in the solar interior are always influenced by the effects from convection, diffusion,pressure,gravitation,etc.,among which the convection is primarily responsible for driving the instability.On the basis of the charact eristic with which the particle number density of chemical compositions changes, we investigate the dynamical behaviors driven by ³He in the proton prot on nuclear reaction chain disturbed by convective motion with the aid of nonequi librium dynamics.The new supercritical oscillations of ³He are found in producing and destroying ³He in the nuclear reaction zone of the sun.The energy generation is therefore oscillating,and then this might change the predicted ⁸B and ⁷Be neutrino fluxes.     

Neutrino oscillations induced by two-loop radiative mechanism

Two-loop radiative mechanism, when combined with an U(1)_L′ symmetry generated by L_e − L_μ − L_τ (=L′), is shown to provide an estimate of Δm²/Δm²_atm εm_e/m_τ, where ε measures the U(1)_L′-breaking. Since Δm²_atm 3.5×10⁻³ eV², we find that Δm² ε10⁻⁶ eV², which will fall into the allowed region of the LOW solution to the solar neutrino problem for ε 0.1.     

Neutron Halos in the Excited States of Spherical Nuclei Near the β-Stable Line

The newly discovered neutron halos in the excited states of nuclei ¹²B, ¹³C, and ²⁰⁹Pb are studied by the relativistic mean-field theory. The calculated binding energies are very close to the experimental ones. The experimentally extracted root-mean-square radii of the last neutron with different occupations in nuclei are well reproduced by calculations. New candidates for the neutron halos in excited states are predicted and are useful for further search of neutron halos in the excited states of stable nuclei.