Bohr-Mottelson转动谱公式参数之间的新关系式

在利用Harris两参数公式研究Bohr-Mottelson转动谱公式参数之间的关系的基础上,改用Harris三参数公式,并由此提出了Bohr-Mottelson转动谱公式参数之间的新关系式,进而用I(I+1)四参数展开式计算了A～60,80,130,140,150,190区超形变偶偶核的基带和锕系和稀土区正常形变核基带,讨论了参数之间的关系,发现新关系式与实验较好地符合.     

Wobbling geometry in a simple triaxial rotor

The spectroscopic properties and angular momentum geometry of the wobbling motion of a simple triaxial rotor are investigated within the triaxial rotor model. The obtained exact solutions of energy spectra and reduced quadrupole transition probabilities are compared to the approximate analytic solutions from the harmonic approximation formula and Holstein-Primakoff formula. It is found that the low lying wobbling bands can be well described by the analytic formulae. The evolution of the angular momentum geometry as well as the K-distribution with respect to the rotation and the wobbling phonon excitation are studied in detail. It is demonstrated that with the increase of the wobbling phonon number, the triaxial rotor changes its wobbling motions along the axis with the largest moment of inertia to the axis with the smallest moment of inertia. In this process, a specific evolutionary track that can be used to depict the motion of a triaxial rotating nucleus is proposed.     

Modeling of 31P-NMR spectra of magnetically oriented phospholipid liposomes: A new analytical solution

³¹P-NMR spectroscopy is widely used for studies of phospholipid liposomes, a commonly used model of a biological membrane. For the correct analysis of ³¹P-NMR spectra of the liposomes it is necessary to take into account that they are deformed by the magnetic field of the spectrometer. The liposomes become ellipsoidal and this affects the lineshape of the spectrum. In the present communication we suggest a new analytical formula for modeling of ³¹P-NMR spectra of the prolate phospholipid liposomes. The formula assumes a Lorentzian broadening function and exactly ellipsoidal shape of the liposomes. Based on the formula a program called P-FIT is designed for the practical analysis of the experimental multicomponent spectra of the prolate liposomes. The versatility of the program developed in a Mathematica environment is demonstrated by simulations of a number of ³¹P-NMR spectra with different complexity.     

q变形三参数公式对偶偶核基带的描述

利用q变形三参数公式,计算了锕系和稀土偶偶核基带转动谱,详细分析了拟合参数值呈现出的规律性.结果表明,q变形转动惯量转子模型能够较精确地描述偶偶核基带转动谱.     

62Sm152核的gR因子

考虑原子核理论中超导效应对g_R因子的影响,在给出偶核g_R因子在推转模型(cranking model)基础上的计算公式之后,利用Nilsson波函数计算了₆₂Sm¹⁵²核的g_R因子。计算结果与实验值符合很好,反映了原子核超导理论的正确性。     

Effect of γ-vibration on high-j rotational bands of odd-A nuclei

A γ-vibrational degree of freedom is incorporated into the particle-symmetric rotor model. The effects of γ-vibration on a high-j rotational band are studied. A characteristic signature splitting of the energy spectra is found to favor the presence of the interaction with the γ-vibration. E2 and M1 intraband transition probabilities of a high-j rotational band are better reproduced in a strongly deformed nucleus when the interaction with the γ-vibration is taken into account. It is found that the interaction with the γ-vibration induces a similar signature-dependent oscillation in E2 transition probabilities to that of the triaxial rotor-particle model.     

Energy Staggering in the High K Rotational Band

Introducing the staggering index S(I) to describe the energy spectra of the λrigid and λ-soft nuclei, it becomes very clear that there are two kinds of energy staggering for which the S(I) -I plots have opposite zigzag behavior. They can be described using the axially asymmebtric rotor model with vibration-rotation coupling and the interaction boson model O(6) limit with three-body potential or the angular momentum projection deformed Hartree-Fock method (PDHF ), respectively. The theoretical predictions for the characteristics of the staggering in high K rotational band are given. Analyzing the experimental data of high K band spectra of the nuclei in the mass range. 160, it is demoastrated that the energy staggering does exist in the high K band. At the same time, some evidences for the shape transition indicated by zigzag phase change of S(I)-I plots are undoubtedly found.     

Noise of a model helicopter rotor due to ingestion of isotropic turbulence

A theoretical and experimental investigation of the noise of a model helicopter rotor due to the ingestion of grid-generated, isotropic turbulence is described. Simulated forward flight and vertical ascent tests were performed with a 0·76 m diameter, articulated model rotor in the United Technologies Research Center Acoustic Research Tunnel. Far field noise spectra and directivity were measured in addition to inflow turbulence intensities, length scales and spectra. Measured inflow turbulence statistics and rotor operating parameters were employed in a theoretical procedure to predict turbulence ingestion noise spectra and directivity. This theoretical formulation represented an absolute level prediction method in that empirical or adjustable constants were not employed. From this study it is concluded that incident turbulence represents a potentially important source of rotor narrowband random (quasi-tonal) and broadband noise. With due regard to the absolute level nature of the prediction method, agreement between theory and experiment is reasonable: quasi-tonal noise at low frequency tends to be overpredicted whereas mid-frequency tonal noise and high frequency broadband noise are well predicted. This theory, therefore, provides a means to predict the contribution of turbulence ingestion noise to overall rotor noise spectra and directivity in cases where reasonable estimates of incident turbulence statistics can be made. Ingestion of main rotor wake turbulence by tail rotors in flight and ingestion of atmospheric turbulence by main and tail rotors in hover would be expected to be the most important sources of turbulence ingestion noise in full scale applications.     

Comparison between formulas of rotational band for axially symmetric deformed nuclei

The experimental rotational spectra of the deformed nuclei available in even-even and odd-A nuclei in the rare-earth and actinide regions are systematically analyzed with several rotational spectra formulas,including Bohr-Mottelson's I(I+l)-expansion,Harris'w2-expansion,ab and abc formulas.It is shown that the simple 2-parameter ab formula is much better than the widely used 2-parameter Bohr-Mottelson's AB formula and Harris'αβ formula.The available data of the rotational spectra of both ground-state band in even-even nuclei and one-quaasiparticle band in odd-A nuclei can be conveniently and rather accurately reproduced by ab formula and abc formula.The moment of inertia and the variation with rotational frequency of angular momentum can be satisfactorily reproduced by ab and abc formulas.     

Alternating Parity Band in Octupole-Soft ~(140)Xe with Axial Vibrational-Rotational Model and Triaxial Rigid Rotor Model

Energies of the yrast positive-and negative-parity excited states in140 Xe are reproduced by two different models considering quadrupole-octupole deformations, namely the axial vibrational-rotational model and the triaxial rigid rotor model, and compared with the stable octupole-deformed222 Th. The origin of the energy difference between the opposite parity sequences is considered from two different mechanisms, the vibration in axial deformed energy minima and the rotation considering the effective triaxial deformation. The success of reproducing the data in both the models implies that these two mechanisms are equivalent on some level for the octupole-soft nuclei. By investigating the probability distributions for projection of total angular momentum in the triaxial rigid rotor model, it is found that such an energy difference is associated with the difference of orientation of the rotational axis.     

Algebraic treatment of multi-step excitation processes in collective nuclei: (II). Electromagnetic excitation of collective nuclear states

Multi-step collective quadrupole excitations in nuclei are described using an algebraic method which does not require a coupled-channel calculation. Adiabatic effects are discussed. Applications to the axially-symmetric deformed rotor, anharmonic quadrupole vibrator, and γ-soft rotor, as well as to transitional nuclei, are presented using the consistent-Q formulation of the interacting boson model.     

Laser probes of intramolecular energy transfer between internal rotation and vibrations in large polyatomics

Laser excited S₁→S₀ fluorescence spectra are obtained from p-fluorotoluene in a supersonic jet in order to probe internal rotational-vibrational coupling. Resolved fluorescence spectra after selective excitation of S₁ levels with high quanta states of the CH₃ internal rotation contain evidence of extensive interactions with isoenergetic vibrational levels. Analogous spectra from states without excitation of the internal rotor show little or no interactions. The results are consistent with a recently developed theory of the intramolecular collisional transfer of rotor energy to the vibrational field.     

Identity for the Exponential-Type Molecule Potentials and the Supersymmetry Shape Invariance

The identity and the supersymmetry shape invariance for a class of exponential-type molecule potentials are studied by introducing a deformed five-parameter exponential-type potential (DFPEP) and via the multi-parameter deformations. It has been shown that the DFPEP is a shape-invariant potential with a translation of parameters. By making use of the shape invariance approach, the exact energy levels are determined for the bound states with zero angular momentum. A class of molecule potentials and their exact energy spectra for the zero angular momentum states are reduced from the DFPEP and a general energy spectrum formula, respectively. The interrelations for some molecule potentials are also discussed.     

Treatment of continua in the shell-model theory of nuclear reactions

It is shown that by a suitable choice of the bound- and continuum-state functions used to perform shell-model calculations, the continuum-continuum interaction may be minimized. Approximate expressions for the scattering matrix elements are derived that are easily evaluated by simple extensions of the conventional shell-model calculations for bound states. Numerical calculations are performed for neutron scattering from ¹²C within the framework of the deformed rotor model and compared with exact coupled-channel calculations.     

磁转动物理——剪刀带与手征双重带

总结和系统介绍了磁转动物理领域的新进展 .阐述了剪刀带的形成机制 ,并论证了在半经典近似和平均场近似下 ,倾斜轴推转模型与粒子转子模型等价 .讨论了原子核在有三轴形变时出现的一种全新的磁转动现象——手征双重带 .并从对称性的角度讨论了剪刀带及手征双重带的能谱特征 .给出了实验上可能存在磁转动带的核区.A new interesting field —— magnetic rotation physics is reviewed. It is proved that the tilted axis cranking (TAC) model is equivalence to the particle rotor model (PRM) under the semi classical and mean field approximations. The shears mechanism and the new discovered phenomena in triaxial deformed nuclei—— chiral doublets are discussed. The possible mass region for these magnetic rotation phenomena is presented.     

Coupling the methyl group in acetamide to phonons: a consistent view of tunnelling and lattice dynamics

Inelastic neutron spectra of acetamide-h5 and acetamide-h2 have been measured at different temperatures below 40K and with high energy resolution in the energy range up to 15 meV. A lattice dynamical model on the basis of atom-atom potentials and electric charges obtained from first principles calculations describes the spectra well if soft internal molecular modes are included. The model is used to reproduce the temperature dependence of the tunnelling transition of the methyl group. For this purpose the density of states is split into that of an isolated rotor in a static field and that of the phonon bath. The effects of the rotor-phonon coupling are evaluated in second order perturbation theory. The broadening of tunnelling lines comes out correctly when the atom atom potentials taken from literature are scaled down by 20%. To get the shift right the strength of the coupling to the lattice needed to be different for the A type symmetry state from that for the E type state. The coupling with the low frequency phonons appears to be very weak.     

Calculation of Neutron Resonance Spacing with Microscopic Theory

Nuclear level spacings calculated with a microscopic theory are compared with spacings determined fromneutron resonance experiment. The gross features of the experimental data due to nuclear shells are reproduced with themicroscopic theory. The experimental data for nuclei with statistically deformed nuclei have also been tested with leveldensity formula including low energy rotational levels. The experimental data for the actinide nuclei and the lanthanidenuclei are found to be consistent with the theory which includes collective rotational levels.     

变形对称双阱势

利用变形双曲函数,将对称双阱势推广为变形对称双阱势模型.证明了该势模型是五参量指数型势模型的特例.运用超对称WKB近似和五参量指数型势模型的能谱公式,获得了变形对称双阱势模型的能谱公式.