A study of the (3He,n) reaction on isotopes of tin

The (³He, n) reaction has been studied on^{112,116,118,120,124}Sn at 25.4 MeV. Angular distributions were measured over the range 0°–25° and the results compared with predictions of zero-range DWBA calculations. In addition to the around-state transitions, L = 0 transitions were also observed to low-lying states in every case. Simple two component wave functions, as well as those obtained from a more sophisticated pairing model, are compared with the data in order to explain the appearance of the anomalously low-lying excited 0⁺ states observed. L = 2 transitions were observed to low-lying 2⁺ states, but the strength of these transitions was much less than expected from the systematics of (t, p) results for N = 50 nuclei.     

NO(X2∏1/2,3/2)v=1←0塞曼跃迁谱及其特性研究

根据塞曼效应理论和激光磁共振光谱技术(LMR)的基本原理,讨论了双原子分子²∏态的塞曼效应特性并导出了解释分子塞曼跃迁的简明代数拟合方程,用这些方程对¹⁴N¹⁶O(X²∏_1/2.3/2)及¹⁵N¹⁶O(X²∏_3/2)(v=1←0)的LMR谱线进行数据拟合,得到塞曼跃迁上、下子能级的g_J因子值和二级塞曼效应因子k₂.将按Hund耦合情形(a)及过渡情形(ab)的理论和拟合方程计算出的磁场位置分别与实验结果相比较,结果表明对NO分子而言,过渡情形(ab)能较真实反映它的耦合情况,且在较高强度磁场下,必须计及二级塞曼修正验证了采用上述代数拟合方程实现新分子LMR谱线标识和指认的可靠性,并提供了系统的处理方法.     

A test for the Cohen-Kurath wave functions in (p,d)-reactions

The experimental data for (p, d)-reactions on the 1p-shell nuclei atE _p –33 MeV are used to test the Cohen and Kurath wave functions and the intermediate coupling. The experimental excitation energies and their order for all law transitions of the 1p-shell nuclei are compared with the theoretical predictions of Cohen and Kurath. The integrated cross-sections (0–90) for these transitions are also compared with their theoretical predictions for one-neutron pick-up. The good agreement between these data indicates a success for the Cohen-Kurath wave functions and for their model of calculations.     

Influence of quantum transitions in the continuum on ionization of atoms in strong fields

The tight-binding method is used to analyze the ionization of a hydrogenlike atom by an intense monochromatic laser field. The orthogonal and normalized basis in which the solution of the time-dependent Schrödinger equation is expanded contains unperturbed wave functions of the discrete spectrum and generalized Coulomb wave functions of the continuum. In the solution of the coupled equations we make use of the fact that the bound-free and free-free transitions are efficient in different regions of complex time. Simplified equations are constructed and investigated. Results of calculations for ionization of a hydrogen atom from its ground state and of the energy distribution of the electrons in strong and superstrong linearly polarized fields are presented. It is shown that in this case the ground state decays completely, and free-free transitions play a defining role in the dynamics of the process. It is established that the total probability of population of the upper Rydberg states abutting the continuum does not exceed 0.05. The range of applicability of the approach is discussed. A comparison with numerical results obtained by other authors is given.     

Raman heterodyne detected magnetic resonance: II. Magnetic transitions of NV centre at level anticrossing region

In the preceding paper [1] we reported both cw and coherent transient measurements carried out in EPR and NMR transitions within the³A ground state of the nitrogen-vacancy centre in diamond using the Raman heterodyne detection technique. In this paper we use these measurements to characterise the nuclear magnetic transitions near a level anticrossing situation. The level anticrossing causes a mixing of the electronic spin and nuclear spin wave functions which results in a greatly enhanced NMR transition moment. The amount of mixing not only affects the dipole moment but, correspondingly, the characteristic relaxation times. In this paper we report the measurement of these parameters in the nitrogen-vacancy centre as a function of applied Zeeman field strength and analyse the results using the spin Hamiltonian formalism. Furthermore, combined with the particular features of the Raman heterodyne technique, such a system represents an ideal testing ground for the nonlinear behaviour of strongly driven transitions. Some results are illustrated, including dynamic Zeeman splitting and gain without inversion.     

Mechanism of superfluid-insulator transition in two-dimensional Bose Hubbard model

To understand the mechanism of Mott transitions in case of no magnetic influence, superfluid-insulator (Mott) transitions are studied for the S = 0 Bose Hubbard model on the square lattice, using a variational Monte Carlo approach. In trial many-body wave functions, we introduce various types of attractive correlation factors between a doubly-occupied site (doublon, D) and an empty site (holon, H), which play a central role for the transition. We propose an improved picture of D–H binding; a Mott transition occurs when the D–H pair length becomes equivalent to the minimum D–D distance, which lengths are appropriately estimated. We confirm this picture is valid for all the wave functions with attractive D–H factors we consider, and point out it can be universal for nonmagnetic Mott transitions.     

Photoionisation using Kohn-Sham wave functions

The determination of photoionisation cross-sections using the Kohn-Sham wave functions from accurate density functional theory (DFT) calculations is considered. The continuum electrons wave function is specified by its momentum measurable in the detector rather than fixed angular momentum and energy. The method is applied to the test case of a water molecule, where the DFT calculations show excellent agreement to experiment in the ionisation energies if a vertical transition is considered. The continuum electron is described by an analytical wave function and the matrix elements are calculated in both in length and velocity form of the dipole operator. The cross-sections agree well with the experiment in particular for the velocity form.     

Two-particle overlaps in a Sturmian basis

Wave functions and energies 0⁺ states of systems of two particles outside an inert core are calculated by diagonalizing a Yukawa interaction in a Sturm-Liouville basis. The wave functions are used in calculations for two-particle transfer cross sections with light and heavy projectiles. Enhancements of the order of 100% to 200% are met when the basis is enlarged to convergence.     

Instantaneous Formulation for Transitions Between Two Instantaneous Bound States and Its Gauge Invariance

We have precisely derived a ＂rigorous instantaneous formulation＂ for transitions between two bound states when the bound states are well-described by instantaneous Bethe-Salpeter （BS） equation （i.e. the kernel of the equation is instantaneous ＂occasionally＂）. The obtained rigorous instantaneous formulation, in fact, is expressed as an operator sandwiched by two ＂reduced BS wave functions＂ properly, while the reduced BS wave functions appearing in the formulation are the rigorous solutions of the instantaneous BS equation, and they may relate to Schroedinger wave functions straightforwardly. We also show that the rigorous instantaneous formulation is gauge-invariant with respect to the Uem（1） transformation precisely, if the concerned transitions are radiative. Some applications of the formulation are outlined.     

Irreducible spin precession theory applied to some topics in atomic and nuclear radio-frequency spectroscopy

Several problems from radio-frequency spectroscopy of atoms and nuclei are treated with irreducible spin precession theory. In the first part, effective field techniques are used to derive analytically single and multiple quantum double resonance lineshapes for atoms with a hyperfine structure in a high magnetic field. In the second part (as an extension to previous work), nuclear resonance signals are calculated for oriented nuclei subject to an electric hexadecapole interaction. Lineshapes of acoustically driven hexadecapole transitions are derived in closed form and compared to experiment. Further, multiple quantum NMR transitions within a hexadecapole shifted nuclear Zeeman structure are calculated, and some distinct features of hexadecapole effects on NMR lineshapes are pointed out. This last case is of current interest due to recent progress in NMR-line narrowing techniques. — In the Appendix, we give lineshape equations for single and double quantum NMR transitions on oriented (I=1)-nuclei subject to an electric quadrupole interaction; these equations are also being used in the atomic rf-spectroscopy calculations. The equations are exact to all orders of the interaction with the external fields.     

Dielectronic recombination rate for the Be-sequence

The dielectronic recombination (DR) rate coefficient α^DR is explicitly calculated for the Mo, Fe, Ar, and Ox target ions of the Be-sequence with four electrons, in the isolated resonance approximation. This work extends the previous study of the Mo³⁸⁺ ions at 1.4, 2.8, and 5.6 keV electron temperatures. Both Δn≠0 and Δn = 0 transitions are considered in detail. The Δn≠0 contribution still dominates, but the Δn = 0 effect becomes quite large for heavy ions. An explicit LS coupling scheme is employed throughout for the dominant transitions calculated here, and contributions from many other intermediate states and cascade transitions are included by comparing the dominant contribution with the more complete Mo³⁸⁺ case and proportionately scaling their effect. Nonrelativistic Hartree-Fock wave functions are used in the evaluation of the Auger and radiative amplitudes, and the continuum wave functions are calculated using the Hartree-Fock direct potential and explicit nonlocal exchange potential. The scaling property of α^DR and its breakdown are examined, and an improved form of the phenomenological formula is proposed.     

Field-induced phase transitions of repulsive spin-1 bosons in optical lattices

We study the phase diagram of repulsively interacting spin-1 bosons in optical lattices at unit filling, showing that an externally induced quadratic Zeeman effect may lead to a rich physics characterized by various phases and phase transitions. We find that the main properties of the system may be described by an effective field model, which provides the precise location of the phase boundaries for any dimension, in excellent agreement with our numerical calculations for one-dimensional (1D) systems. Thus, our work provides a quantitative guide for the experimental analysis of various types of field-induced quantum phase transitions in spin-1 lattice bosons. These transitions, which are precluded in spin-1/2 systems, may be realized by using an externally modified quadratic Zeeman coupling, similar to recent experiments with spinor condensates in the continuum.     

Properties of isovector 1+ states in A=28 nuclei and nuclear muon capture

A method is proposed for taking into account, in a calculation of partial rates of muon capture by nuclei, experimental information about strength functions for Gamow-Teller and isovector M1 transitions. The method, which amounts to choosing an orthogonal transformation that acts in the subspace of wave functions for excited states, requires neither modifying transition operators nor introducing effective charges. The matrix of the above transformation is constructed as a product of the matrices of reflection in a plane. All calculations are performed on the basis of the multiparticle shell model. Numerical results are obtained for isovector states in A=28 nuclei. Strength functions for Gamow-Teller and isovector M1 transitions in ²⁸Si are considered, and the lifetimes of 1⁺ states in ²⁸Al and the branching fractions for gamma decays of this state are calculated. Owing to taking into account experimental information about the properties of isovector states, the branching fractions for the γ decays of the 1⁺ state at 2.201 MeV in ²⁸Al are successfully described for the first time. The above transformation of the wave functions changes substantially the distribution of partial rates of allowed muon capture by a ²⁸Si nucleus among the 1⁺ states of the final nucleus ²⁸Al in relation to the results of the calculations with the eigenfunctions of the Hamiltonian of the multiparticle shell model. The muon-capture rates calculated with the transformed functions agree well with experimental data.     

Study of some two-nucleon pick-up reactions in the 1p shell with 39.8 MeV protons

Differential cross sections at a proton energy of 39.8 MeV (lab) have been measured for the following reactions (energies in MeV): ¹²C(p,τ)¹⁰B(g.s., 0.72, 1.74, 2.15, 3.59), ¹⁴C(p, t)¹²C(g.s., 4.43), ¹⁴N(p, τ)¹²C(g.s., 4.43), and ¹⁶O(p,τ)¹⁴N(g.s., 2.31, 3.95). A zero-range DWBA analysis of the data has been performed using the 1p shell wave functions of Cohen and Kurath. The fits we find are overall somewhat worse in shape than those found in the (p, t) survey of the 1p shell performed by Kahana and Kurath, the principal reason being that of the (p, τ) transitions which proceed with both L = 0 and L = 2 components we find several which occur with a much weaker L = 0 strength than the calculations predict. When ratios of experimental integrated cross sections to DWBA integrated cross sections are compared for all transitions, an rms deviation about the mean of 39% of the mean is found, whereas if only ratios for transitions from a given target nucleus are compared, then the rms deviations are considerably smaller.     

Reconstruction of all-electron wave functions from pseudo-single-electron orbitals and calculations of the probabilities of X-ray transitions

The probabilities of x ray dipole transitions in free atoms C, O, Al, Si, and Ge and their ions are calculated. The wave functions of the initial and final states were calculated in terms of the density functional method using norm-conserving and ultrasoft pseudopotentials. Various methods of reconstruction of all-electron wave functions from pseudo-single-electron orbitals are considered. Using the reconstructed all-electron wave functions, the transition probabilities are calculated in the velocity and length gauges. The calculations are compared with the results of atomic all-electron calculations. At least for ultrasoft pseudopotentials, the error of the reconstruction procedure used in the study is about 1–3%.     

Magnetooptical studies of Cd1−xMnxTe quantum wells with parabolic confining potential

We report on magnetooptical studies of II–VI semiconductor quantum wells with a parabolic shape of the potential grown on the basis of Cd_1−xMn_xTe. Photoluminescence excitation measurements revealed a series of peaks equidistant in energy associated with interband optical transitions between “harmonic oscillator states”. We observed the Zeeman splitting for heavy-hole excitons up to the subband index n=5. From the comparison of the experimental data with numerical calculations for the Zeeman splitting it was possible to determine the correct shape of the potential.     

Scattering of Cu(1 0 0) image state electrons from single Cu adatoms and vacancies: A comparative study

A theoretical study of the electron dynamics in image potential states on Cu(1 0 0) surfaces with different types of defects (Cu adatoms and Cu vacancies) is presented for low defect density at the surface. A wave packet propagation approach is employed for the electron scattering calculations, where the defect induced potentials are obtained from an ab initio density functional study. Scattering of the image state electron by a defect induces inter-band and intra-band transitions leading, respectively, to the population decay and to the dephasing of the image states. Comparison of the respective effects of adatoms and vacancies shows that Cu adatoms are much more efficient in inducing population decay and dephasing of the image potential states. Present results for the case of Cu adatoms are compared with available time-resolved two-photon photoemission data.     

Effect of magnetic field on electron spectrum and probabilities of intraband quantum transitions in spherical quantum-dot-quantum-well

The effect of magnetic field on electron energy spectrum, wave functions and probabilities of intraband quantum transitions in multilayered spherical quantum-dot-quantum-well (QDQW) CdSe/ZnS/CdSe/ZnS is studied. Computations are performed in the framework of the effective mass approximation and rectangular potential barriers model. The wave functions are expanded over the complete basis of functions obtained as exact solutions of the Schrodinger equation for the electron in QDQW without the magnetic field.It is shown that magnetic field takes off the spectrum degeneration with respect to the magnetic quantum number and changes the localization of electron in the nanostructure. The field stronger effects on the spherically-symmetric states, especially in the case of electron location in the outer potential well. The magnetic field changes more the radial distribution of probability of electron location in QDQW than the angular one. The oscillator strengths of intraband quantum transitions are calculated as functions of the magnetic field induction and their selection rules are established.     

Schlieren imaging of nano-scale atom-surface inelastic transition using a Fresnel biprism atom interferometer

Surface-induced exo-energetic inelastic transitions among atomic Zeeman states in a magnetic field (“van der Waals – Zeeman” transitions) are useable as tuneable beam splitters. A transversally coherent atom beam impinging a pair of opposite surfaces (e.g. 2 edges of a slit or of an ensemble of periodic slits) gives rise to two coherently diffracted wave packets. Within the wave packet overlap, non-localised interference fringes of the Young-slit type are predicted. From the diffraction pattern observed in the Fraunhofer regime (Schlieren image), detailed information about the transition amplitude on a scale of a few nanometers should be derived.