用光电离技术探测钐原子的奇宇称束缚激发态的光谱

采用光电离探测方法,对钐原子奇宇称束缚激发态进行了系统研究.通过设计三条不同的激发路径, 采用共振激发方式,先将钐原子分三步从基态激发到不同的束缚激发态,然后采用光电离手段对其进行探测. 通过对第三步激发光的波长进行大范围的扫描,在同一能域内获得了三组不同的光谱. 通过比对三条路径所得到的三组光谱,不仅精确确定了大量奇宇称束缚激发态的能级位置, 而且还获得了相应跃迁的相对强度的信息.最后,通过运用三条不同的激发路径的选择定则, 还确定了上述能级的总角动量. 关键词： 钐原子 束缚激发态 奇宇称 光电离探测     

Donor-like excited states of exciton bound to neutral acceptor in ZnTe

Photoexcitation spectroscopy has been used to study the excited states of the neutral c-acceptor bound exciton complex A^c₁ in ZnTe. We have detected four excited states at ～ 11.2 meV above the bound exciton ground state. Zeeman effects on these excited states have also been studied. The results show that they correspond to excitations of the bound electron to donor-like 2p and 2s orbital states. This represents an unambiguous experimental evidence of the pseudo-donor model previously suggested by Rühle and Bimberg for acceptor bound exciton complexes when m_e ? m_h.     

Geometric quantities of lower doubly excited bound states of helium

Expectation values of single electron and interelectronic geometric quantities such as $\langle r\rangle$, $\langle r_{12}\rangle$, $\langle r_<\rangle$, $\langle r_>\rangle$, $\langle \cos\theta_{12}\rangle$ and $\langle \theta_{12}\rangle$ are calculated for doubly excited $2{\rm p}n{\rm p}\,{}^1P^{\,\rm e}\,(3\leq n\leq5),\, 2{\rm p}n{\rm p}\,{}^3\!P^{\,\rm e}\,(2\leq n\leq5)$ and $2{\rm p}n{\rm d}\,{}^{1,3}D^{\,\rm o}\,(3\leq n\leq5)$ states of helium using Hylleraas-$B$-spline basis set. The energy levels converge to at least 10 significant digits in our calculations. The extrapolated values of geometric quantities except for $\langle \theta_{12}\rangle$ reach 10 significant digits as well; $\langle \theta_{12}\rangle$ reaches at least 7 significant digits using a multipole expansion approach. Our results provide a precise reference for future research.     

Chiral three-nucleon forces and bound excited states in neutron-rich oxygen isotopes

Astatine isotopes can be produced in liquid lead-bismuth eutectic targets through proton-induced double charge exchange reactions on bismuth or in secondary helium-induced interactions. Models implemented into the most common high-energy transport codes generally have difficulties to correctly estimate their production yields as was shown recently by the ISOLDE Collaboration, which measured release rates from a lead-bismuth target irradiated by 1.4 and 1 GeV protons. In this paper, we first study the capability of the new version of the Liège intranuclear cascade model, INCL4.6, coupled to the deexcitation code ABLA07 to predict the different elementary reactions involved in the production of such isotopes through a detailed comparison of the model with the available experimental data from the literature. Although a few remaining deficiencies are identified, very satisfactory results are found, thanks in particular to improvements brought recently on the treatment of low-energy helium-induced reactions. The implementation of the models into MCNPX allows identifying the respective contributions of the different possible reaction channels in the ISOLDE case. Finally, the full simulation of the ISOLDE experiment is performed, taking into account the likely rather long diffusion time from the target, and compared with the measured diffusion rates for the different astatine isotopes, at the two studied energies, 1.4 and 1 GeV. The shape of the isotopic distribution is perfectly reproduced as well as the absolute release rates, assuming in the calculation a diffusion time between 5 and 10hours. This work finally shows that our model, thanks to the attention paid to the emission of high-energy clusters and to low-energy cluster induced reactions, can be safely used within MCNPX to predict isotopes with a charge larger than that of the target by two units in spallation targets, and, probably, more generally to isotopes created in secondary reactions induced by composite particles.     

Uniaxial stress effects and excited states for multiple bound excitons

The theoretical model for multiple bound excitons (MBE) recently introduced by Dean et al¹ is used to discuss uniaxial stress effects in silicon. The fine structures observed in MBE spectra for SiC and Si are qualitatively strikingly similar. However, the interpretation of the strongest features in terms of a specific model for excited states suggested by Kirczenow² and Thewalt³ is not valid for SiC.     

Observation of bound states of interacting vector solitons

We report experimental observation of bound states formed by two well-separated vector spatial solitons as the result of a force balance between vector-soliton components. We also demonstrate a link between such soliton bound states and two-hump, two-mode solitons, along with the induced coherence effect observed for incoherently interacting solitons.     

Low lying excited states of the bound exciton in a spherical model

We report the calculation of the S-like excited states of the bound exciton produced by exciting the outer particle. We find that in spherical model for all but very small (?0.03) and very large (?10) mass ratios these states are unbound. We have tentatively identified some of the excited states as being those observed for the donor bound exciton in Gap.     

Lifetimes of bound states in 15O

The lifetime values of 8.2 ± 1.0, > 3000, < 2.5, 16.0 ± 2.5 and 750 ± 200 fs for the first, second, third, fifth and sixth bound states in ¹⁵O, at 5183, 5241, 6176, 6859 and 7276 keV, respectively, were determined with the DSA method through the ¹⁴N(p, γ)¹⁵O reaction. The experimental correction factors of the nuclear and electronic stopping powers were used in the DSA analysis. In the calculations the Monte Carlo method was employed. The transition strengths are discussed in terms of shell-model calculations.     

Experimental study of highly excited even-parity bound states of the Sm atom

In this work, a three-step autoionization detection method and direct photoionization detection method are employed to measure the highly excited even-parity states of the Sm atom in the energy region between 36360~cm^-1 and 40800~cm^-1. Comparisons between the results from the two detection techniques enable us to discriminate the Rydberg states from the valence states in the same energy region with the information of level energies, possible J values and their relative intensities. Furthermore, in the experiment two different excitation schemes are designed to obtain the spectra of highly excited even-parity states of the Sm atom. With a detailed analysis of the experimental data, this work not only confirms the results about many spectral data from the literature with different excitation schemes, but also reports new spectral data on 29 Rydberg states and 23 valence states.     

Correlated wave functions to approach the bound excited states of Li- and Be-

Explicitly correlated wave functions including a Jastrow factor to take into account the dynamical correlation effects, and a multi determinant model wave function to account for the non–dynamical correlations are used to study some metastable excited states of the negative ions Li^- and Be^-. A detailed analysis of one– and two–body properties has been carried out for these states. In particular the single–particle density as well as both the two–body inter electronic and center of mass densities have been obtained. All the calculations have been performed by using the variational Monte Carlo method.     

The first excited states of 9Be and 9B

It is found here that the 1/2⁺ first excited state of ⁹Be is a virtual state with the energy of −23.5 KeV. The line shape for the excitation of the state is approximated with a simple analytic form based on the effective range expansion. The partner in ⁹B of this state is found to be a resonance with a maximum in the peak at about 1.1 MeV, FWHM of 1.5 MeV, and complex energy of 0.6 −i0.75 MeV. The line shape for its excitation is calculated in terms of the p−⁸Be phase shift. The phase shifts are obtained from N−⁸Be effective potentials deduced from the data on the photodisintegration of ⁹Be. A possibility for direct extraction of the energy of the resonant state from experimental data is also discussed, and an expression for a residue at a virtual state pole in terms of a quadrature taken over the virtual state eigenfunction is given. Received: 23 March 1998 / Revised version: 3 September 1998     

Observation of orbitally excited B(s) mesons

We report the observation of two narrow resonances consistent with states of orbitally excited (L=1) B_(s) mesons using 1 fb;(-1) of pp[over ] collisions at sqrt[s]=1.96 TeV collected with the Collider Detector at Fermilab II detector at the Fermilab Tevatron. We use two-body decays into K- and B+ mesons reconstructed as B(+)-->J/psiK(+), J/psi-->mu(+)mu(-) or B(+)-->D[over ](0)pi(+), D[over ](0)-->K(+)pi(-). We deduce the masses of the two states to be m(B_(s1))=5829.4+/-0.7 MeV/c(2) and m(B_(s2);(*))=5839.6+/-0.7 MeV/c;(2).     

Observation of soliton bound states in a graphene mode locked erbium-doped fiber laser

We report on the experimental observation of bound states of solitons in a graphene mode locked erbium-doped fiber laser. By using graphene as a saturable absorber, we have obtained stable, single and bound soliton pulses, the latter with a full width at half maximum (FWHM) of 1.49 ps and a fixed pulse separation of 2.46 ps. Our results once again show that bound soliton pulses is an intrinsic feature of fiber lasers independent of the exact mode locking mechanism.     

Topological bound states

In the tight binding approximation, it has been shown that a peculiar type of electronic states localized near the topology change point exists in branching molecules and quantum conductors. Bound states of this type exist both below and above the allowed band, i.e., for both electrons and holes; this property fundamentally differentiates these states from the bound states formed in the minimum of the potential energy. The damping decrement of the wavefunction is independent of the band parameters and is an invariant determined by the characteristic of topology. The tunnel interaction between the topological bound states significantly determines the change in the electronic spectrum of the molecular systems in configuration transitions.     

Threshold bound states

Relationships between the coupling constant and the binding energy of threshold bound states are obtained in a simple manner from an iterative algorithm for solving the eigenvalue problem. The absence of threshold bound states in higher dimensions can be easily understood.