The F-spin symmetric limits of the neutron-proton interacting boson model

The F-spin symmetric limits U(5), SU(3), and O(6) of the neutron-proton interacting boson model are studied. The conditions for and consequences of F-spin symmetry are investigated. In each of the three limits closed expressions for the following properties are given: the excitation energies; the M1, E2, and M3 excitation strengths from the ground state to all 1⁺, 2⁺, and 3⁺ states; the M1 and E2 decay of the nonsymmetric 1⁺ and 2⁺ states; and the dipole and quadrupole moments of maximal F-spin states and of the nonsymmetric 1⁺ and 2⁺ states. The predictions for these properties are compared with the experimental data.     

Spectroscopic properties of SbH

Relativistic configuration interaction calculations which include spin-orbit interaction are carried out for nine low-lying ω-ω states and four λ-s states. Spectroscopic properties of six bound ω-ω states are reported. These calculations not only enable assignment of the experimentally observed X₁, X₂, A₁, A₂, and B states but also predict the properties of other electronic states (0⁺(II), 0⁺(IV), 2, 2(II), 1(II), 0⁻) which are yet to be observed. The dissociation energy of SbH is predicted to be 2.7 ± 0.2 eV.     

Stability properties and the KMS condition

First we derive stability properties of KMS states and subsequently we derive the KMS condition from stability properties. New results include a convergent perturbation expansion for perturbed KMS states in terms of appropriate truncated functions and stability properties of ground states. Finally we extend the results of Haag, Kastler, Trych-Pohlmeyer by proving that stable states ofL ¹-asymptotically abelian systems which satisfy a weak three point cluster property are automatically KMS states. This last theorem gives an almost complete characterization of KMS states, ofL ¹-asymptotic abelian systems, by stability and cluster properties (a slight discrepancy can occur for infinite temperature states).Supported during this research by the Norwegian Research Council for Science and Humanities     

Explorative computational study of the singlet fission process

Different ab initio methods, namely multi-reference and nonorthogonal configuration interaction techniques, are explored for their applicability in studying the singlet fission problem. It has been shown for 2-methyl-1,5-hexadiene that the ¹TT state can be identified using multi-reference techniques. The geometrical and vibrational properties of the ¹TT state are such that they can be approximated with those of the ⁵TT state. A proof of principle is given for the calculation of the singlet fission pathway driven by nuclear motion: efficient singlet fission can take place if the ¹TT and S₁ states are close in energy with a large non-adiabatic coupling matrix element at the S₁ geometry, and the energy of the S₀ state is well below that of the ¹TT state at the ¹TT geometry.

The nonorthogonal configuration interaction method was used to treat a tetracene trimer. It has been shown that the first excited states can be interpreted as delocalised states; interaction with charge-transfer base states plays an important role. The ¹TT states are localised on one pair of molecules. The electronic coupling between the diabatic S[n] and ¹TT[m] states is in the meV range, confirming previous estimates. The charge-transfer base states enhance the coupling between the S[1]/S[2] and ¹TT[2] excited states.     

Structure of even-even beryllium isotopes studied by AMD+GCM method

The ground state properties and the properties of low-lying states of the even-even⁶Be-¹²Be beryllium isotopes are investigated using the extended version of the Antisymmetrized Molecular Dynamics Multi-Slater Determinant model. The theoretical method is found to be very useful to study ground state properties of various nuclei covering light unstable nuclei. Many experimental data can be successfully reproduced by the adopted approach. Binding energies, the energies of the 2 ₁ ⁺ states, electromagnetic transition strengths and quadrupole moments of proton and neutron distribution are calculated. This work is supported in part by Grant-in-Aid for Scientific Research (13740145) from the Ministry of Education, Science and Culture.     

Low-lying electronic states of LiF molecule with inner electrons correlation

The potential energy curves and dipole moments of the low-lying electronic states of LiF molecule are performed by using highly accurate multi-reference configuration interaction with Awcv5z basis sets. 1s, the inner shell of Li is considered as the closed orbit, which is used to characterise the spectroscopic properties of a manifold of singlet and triplet states. 16 electronic states correlate with two lowest dissociation channels Li(²S)+F(²P) and Li(²P)+F(²P) are investigated. Spectroscopic parameters of the ground state X¹Σ⁺ have been evaluated and critically compared with the available experimental values and the other theoretical data. However, spectroscopic parameters of 1³Π, 1¹Δ, 1¹Σ^?, 1¹Π, 1³Σ⁺, 2³Σ⁺, 1³Δ, 1³Σ^?, 2³Π, 2¹Π, 3³Π, 3¹Π and 3³Σ⁺ states are studied for the first time. These 13 excited states have shallow potential wells, and the dispersion coefficients of these excited states are predicted. In additional, oscillator strengths of excited states at equilibrium distances are also predicted.     

AuZn和AuAl分子基态与低激发态的势能函数与热力学性质

用密度泛函理论B3LYP方法计算研究AuZn和AuAl分子基态与低激发态的结构与势能函数,导出分子的光谱数据.结果表明,AuZn和AuAl分子基态分别为X²Σ和X¹Σ,基态与低激发态的势能函数均可用Murrell-Sorbie函数来表达.AuZn分子低激发态a⁴Σ的绝热激发能为43529kJ/mol,AuAl分子低激发态a³Σ的绝热激发能为19991kJ/mol.计算固体AuZn和AuAl的内能和熵时,近似以气体分子的电子能和振动能代替固体分子的内能,用电子熵和振动熵代替固体分子的熵.在此近似下,计算得到AuZn和AuAl基态与低激发态固态分子生成反应热力学性质与温度的关系. 关键词： AuZn和AuAl B3LYP 热力学性质 势能函数     

Theoretical study of molecular properties of low-lying electronic excited states of H2O and H2S

Geometries, excitation energies, dipole moments and dipole polarisability tensor components of the ground and four lowest excited states ³ B ₁, ¹ B ₁, ³ A ₂, ¹ A ₂ of the H₂O and H₂S molecules were calculated at the CASSCF, CASPT2, CCSD and CCSD(T) level of approximation. Vertical excitation and equilibrium transition energies of these states, having the Rydberg character, are reported too. Properties of both molecules in the ground and in low lying excited states are compared and discussed from the point of view of their molecular electronic structure. Upon excitation we observe dramatic changes of dipole moments and polarisabilities with respect to the ground state. We stress the change of the polarity of H₂O in all excited states accompanied by the enhancement of the dipole polarisability by an order of magnitude. Large, even if less pronounced, are changes of electric properties of H₂S in its excited states. Dipole moments and dipole polarisabilities of ³ B ₁, ¹ B ₁ states of H₂S and H₂O behave quite analogously in comparison to their respective ground state. The general pattern of properties for both molecules in their ³ A ₂ and ¹ A ₂ excited states is more different due to a pronounced participation of the sulphur d-orbitals in these states of the H₂S molecule.     

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.     

利用自电离探测技术研究Sm原子Rydberg态光谱

采用孤立实激发与自电离探测技术相结合的方法对Sm原子偶宇称高激发态进行了系统研究.按照不同的自电离通道将所测数据进行了分类和比较,并进行了详细讨论.不仅报道了许多收敛于不同电离限的Rydberg态的能级位置和跃迁的相对强度等信息,而且还把处于同一能域内的Rydberg态和价态进行了辨识.另外,不但提供了一种有效识别不同类型的高激发态的鉴别技术,而且还对处于41800 cm^-1到43800 cm^-1能域内的Rydberg态和价态的光谱特性进行了详细分析和讨论. 关键词： 自电离探测 Rydberg态 Sm原子     

States of the 12N Nucleus with Increased Radii

The differential cross sections for the ¹²C(³He, t)¹²N reaction leading to formation of the 1⁺ (ground state), 2⁺ (0.96 MeV), 2⁻ (1.19 MeV), and 1⁻ (1.80 MeV) states of ¹²N are measured at E(³He) = 40 MeV. The analysis of the data is carried out within the modified diffraction model and distorted wave Born approximation. Increased rms radii have been obtained for the ground, 2⁻ (1.19 MeV), and 1⁻ (1.80 MeV) states. We revealed that ¹²B, ¹²N, and ¹²C in the isobaric analogue states with T = 1, and spin-parities 2⁻ and 1⁻ have increased radii and exhibit properties of neutron and proton halo states.

     

Generalized Heisenberg theory of turbulence

The properties of the low-lying excited states of⁵³Mn have been investigated in the framework of the intermediate-coupling unified nuclear model. In the present calculations, it was assumed that three holes in the 1f _7/2 proton shell, which undergo excitations, are coupled to the quadrupole vibrations of the doubly even core. Energy levels and electromagnetic properties have been calculated. In most cases, the results are found to be in good agreement with the experimentally observed values for the low-lying excited states in⁵³Mn. The results are also compared with those obtained from other models.     

The structure of 32S II. Shell model interpretation

The properties of positive-parity states in ³²S are compared to predictions of shell model calculations within the complete s-d basis space using the universal s-d shell Hamiltonian. The experimental T = O spectrum is reproduced to excitation energies between 10 and 11.7 MeV, depending on the level spins. The T = 1 spectrum is known and reproduced for the first five 5 MeV in excitation in general and for the first 8 MeV in the case of I^π = 1⁺ states. Altogether the excitation energies of 80 positive-parity states are reproduced with a rms deviation of 200 keV. A calculation of radiative widths and branching ratios for γ-decay which uses effective charges and free-nucleon g-factors yields good general agreement with experiment. The need for effective g-factors is felt only in the rare cases of transitions which are governed by the isovector d_3/2 → d_5/2 M1 matrix element. The spectrum of negative parity, T = 1 states is understood in terms of the weak-coupling model while that of the T = 0 states is comprised of octupole-quadrupole phonon multiplets. Positive-parity states from outside the s-d configuration are first observed between 9.5 and 10.5 MeV excitation energy.     

Magnetic dipole transitions and proton-neutron degrees of freedom in nuclear deformation

The M1 transitions between low-lying collective states are discussed from the viewpoint of the Proton-Neutron Interacting Boson Model, with particular emphasis on the mixed-symmetry states. Mixed-symmetry 2⁺ states are studied for⁵⁶Fe and⁵⁴Cr in terms of realistic and large-scale shell-model calculations, including M1 properties. The Doorway-state character of the mixed-symmetry 2⁺ state is proposed with examples in these nuclei. The possible candidate of the mixed-symmetry 2⁺ state in¹³⁴Ba is analyzed based on recent experiment by Molnaret al. on M1 transitions. The M1 transitions from the quasi-γ to quasi-g bands in γ-unstable or O(6) nuclei are discussed next, by taking Ba isotopes as an example. It is suggested that such M1 transitions are enhanced compared to axially symmetric nuclei as an indication of softness towards proton-neutron incoherent motion in γ-unstable nuclei,i.e., mixture of mixed-symmetry states. A new mirror-type symmetry is introduced for γ-unstable nuclei, and the M1 selection rule due to this symmetry is presented, making 4 ₂ ⁺ →4 ₁ ⁺ transition allowed but 3 ₁ ⁺ →2 ₁ ⁺ forbidden, for instance.     

Origin of three-body resonances

We expose the relation between the properties of the three-body continuum states and their two-body subsystems. These properties refer to their bound and virtual states and resonances, all defined as poles of the S-matrix. For one infinitely heavy core and two non-interacting light particles, the complex energies of the three-body poles are the sum of the two two-body complex pole-energies. These generic relations are modified by center-of-mass effects which alone can produce a Borromean system. We show how the three-body states evolve in ⁶He, ⁶Li, and ⁶Be when the nucleon-nucleon interaction is continuously switched on. The schematic model is able to reproduce the main properties in their spectra. Realistic calculations for these nuclei are shown in detail for comparison. The implications of a core with non-zero spin are investigated and illustrated for ¹⁷Ne ( ¹⁵O + p + p). Dimensionless units allow predictions for systems of different scales.     

Multireference configuration interaction study of ground and low-lying excited states of the AlC radical

This work explored the spectroscopic parameters and vibrational properties of the 21 Λ–S and 42 Ω states of the AlC radical. The PECs were calculated with the CASSCF method, which was followed by the icMRCI+Q approach. The A⁴Π, a²Π, 5²Π, 2²Δ, and 1²Φ states as well as the first well of B⁴Σ^? state were inverted with the spin–orbit coupling (SOC) effect included; the 1⁴Δ, 1⁴Σ⁺, and 2²Σ^? states as well as the second wells of the B⁴Σ^?, 2²Σ⁺, 3²Σ⁺, 4²Π and 5²Π states were weakly bound, which well depths were less than 650 cm^?1; the B⁴Σ^?, 2²Σ⁺, 3²Σ⁺, 4²Π, 5²Π, and 2²Δ states had double wells and the second wells of these states except for B⁴Σ^? had only several vibrational states; the avoided crossings existed between the 2²Σ⁺ and 3²Σ⁺ states, the 3²Σ⁺ and 4²Σ⁺ states, the B⁴Σ^? and 3⁴Σ^? states, the 2²Δ and 3²Δ states, the 4²Π and 5²Π states, the 5²Π and 6²Π states, as well as the 2⁴Π and 3⁴Π states. The extrapolation scheme, core–valence correlation and scalar relativistic corrections were included. The spectroscopic parameters and vibrational properties were determined. The TDM curves between two different Λ–S states were calculated and Franck–Condon factors of some transitions were evaluated. The SOC effect on the spectroscopic and vibrational properties was evaluated.     

The effect of expansion of the shell model space on the structure of the mass-15 nuclei

The structure of the natural and unnatural parity states of the¹⁵N-¹⁵O mirror pair, as well as theT=3/2 analogue states of¹⁵C, is discussed in terms of shell model calculations with a modified surface delta two-body interaction. The inert core is recomposed from⁴He to¹²C and the configuration space is systematically expanded to allow for an increasing number of particle excitations from the 1p into the 2s-1d shell. The relative importance of the 2s 1/2, 1d 5/2 and 1d 3/2 orbitals are evaluated. Some electromagnetic properties of levels are also calculated.     

Low-lying electronic states of BeH+ with the effect of inner electrons

The potential energy curves of the low-lying electronic states of BeH⁺ molecular ion are performed by using highly accurate multi-reference configuration interaction with AV5Z basis sets for H atom and ACV5Z basis set for Be atom, 1s inner shell of Be is considered as the core orbit and the active orbit, respectively, which are used to characterise the spectroscopic properties of a manifold of singlet and triplet states. Fourteen electronic states correlated with eight dissociation channels are investigated, we have found that the a³Σ⁺ and c³Σ⁺ both are bound states, the 3³Σ⁺ possesses double wells, and the C¹Σ⁺, 3³Σ⁺, 2³Π, 2¹Π, 1¹Δ, 1³Δ, 2³Δ and 2¹Δ states are studied for the first time. Transition dipole moment, Franck–Condon factors q_υ′υ^″ and Einstein coefficients A_υ′υ^″ for A¹Σ⁺–X¹Σ⁺, 2¹Π–B¹Π, c³Σ⁺–a³Σ⁺ and b³Π–a³Σ⁺ systems have been calculated. Radiative lifetime of A¹Σ⁺–X¹Σ⁺ band system has also been determined.     

Halo or skin in the excited states of some light mirror nuclei

The properties of three pairs of mirror nuclei ¹³N- ¹³C, ¹⁵N- ¹⁵O and ²¹Na- ²¹Ne (these mirror nuclei are all made of a good inert core plus an unpaired valence nucleon) are investigated by using the nonlinear relativistic mean-field (RMF) theory. It is found that the calculated binding energies with two different parameter sets are very close to the experimental ones for both the ground states and the excited states except for the large deformed nuclei. The calculations show that the 2s_1/2 excited states of ¹⁵N and of ²¹Na are both weakly bound with a proton halo and a proton skin (or a pigmy proton skin), respectively. In addition, the 1d_5/2 excited state of ¹³C and the 2s_1/2 excited state of ¹⁵O are also weakly bound with a neutron skin, respectively. The ratio of the valence nucleon radius to matter radius is deduced and it can be regarded as an additional criterion for the existence of exotic structure. The unbound 2s_1/2 and 1d_5/2 excited states of ¹³N are also discussed.     

Nematic-phase N.M.R. investigation of rotational isomerism: conformations of 2-furanaldehyde

An unrestricted Hartree-Fock molecular orbital procedure has been used to compute some properties of the lowest-lying spectroscopic states of NH₂, BH₂ and CH₂ ⁺. Computed bond angles for the ²B₁ and ²A₁ states of NH₂ and BH₂ are in good agreement with experimental data; bond lengths are about 6 per cent too great. Among other states for which predictions are made, the ²B₂ state of NH₂ has novel equilibrium geometry, with a predicted angle of 26·57°.

Dissociation products are considered. It is predicted that for the isoelectronic systems CH₂ ⁺ and BH₂ there is a contrast:

Other properties, such as isotropic coupling constants, force constants and dipole moments, are also reported.