用B样条函数方法研究碱金属原子里德堡态在静电场中的性质

由原子的模型势出发,利用B样条函数方法研究了钾和铯原子的里德堡态在静电场中Stark态能级反交叉位置以及微波场中钾原子的多光子共振吸收谱.研究表明我们的结果与实验和其他理论结果符合得很好.     

用B-样条函数研究静电场中锂原子里德伯态的性质

用B-样条函数展开方法,结合原子的单电子势模型研究了静电场中锂原子里德伯态的性质. 所得到的Stark能级图、反交叉位置、反交叉宽度以及振子强度与已有的实验和其他理论结果符合得很好. 表明该方法是一种有效的研究静电场中碱金属原子性质的方法. 最后,在数值上研究了锂原子里德伯态振子强度谱随静电场场强的演化特征. 关键词： B-样条函数 振子强度 反交叉位置 反交叉宽度     

太赫兹场中里德堡铷原子的相干操控

采用含时多态展开方法研究了太赫兹场中里德堡铷原子布居数迁移的动力学过程,计算了一个太赫兹脉冲序列与三能级里德堡铷原子系统相互作用后的布居数分布,以及多脉冲序列对多量子态里德堡铷原子系统的相干操控,给出了同一主量子数n中不同角量子数l态布居数的含时演化过程.结果表明:通过优化太赫兹脉冲序列参数,铷原子布居数可由初态被抽运到较高的目标态,在太赫兹频率范围实现里德堡原子的操纵与控制.     

太赫兹场中里德堡铷原子的相干操控

采用含时多态展开方法研究了太赫兹场中里德堡铷原子布居数迁移的动力学过程,计算了一个太赫兹脉冲序列与三能级里德堡铷原子系统相互作用后的布居数分布,以及多脉冲序列对多量子态里德堡铷原子系统的相干操控,给出了同一主量子数n中不同角量子数l态布居数的含时演化过程.结果表明:通过优化太赫兹脉冲序列参数,铷原子布居数可由初态被抽运到较高的目标态,在太赫兹频率范围实现里德堡原子的操纵与控制.     

用B-样条函数研究静电场中锂原子里德伯态的性质

用B-样条函数展开方法，结合原子的单电子势模型研究了静电场中锂原子里德伯态的性质. 所得到的Stark能级图、反交叉位置、反交叉宽度以及振子强度与已有的实验和其他理论结果符合得很好. 表明该方法是一种有效的研究静电场中碱金属原子性质的方法. 最后，在数值上研究了锂原子里德伯态振子强度谱随静电场场强的演化特征.     

ns6s里德堡分子的势能曲线

里德堡电子与基态原子的低能电子散射形成长程里德堡分子,这种分子具有大的轨道半径,丰富的振动能级和永久电偶极矩等特点。本文考虑铯里德堡ns态与(n-4)l(n为主量子数,l为角量子数且l2)近简并态的非绝热耦合与p-波共振现象,数值计算了长程铯里德堡分子的势能曲线。分析ns6s(n=32-36)态分子最外层势阱,研究了长程里德堡分子的势阱深度、平衡距离与主量子数n的关系,为实验研究长程里德堡分子提供理论依据。     

微波调制的里德堡原子集体量子跳跃

对于一个三能级原子体系,原子的两个基态能级通过微波耦合起来,其中一个基态能级可被激发到里德堡态,从而可观察量子跳跃现象.本文采用量子轨线方法研究了微波调制的里德堡原子集体量子跳跃.研究结果表明,微波耦合基态能级可以提高光子关联,增强光子聚束效应,即使较少的原子中也可以观察到系统在高里德堡占据数态和低里德堡占据数态之间的切换.这一结果为将来进一步研究里德堡自旋晶格中的多体动力学提供了新思路.     

镁原子里德堡能级的计算

依据最弱受约束电子势模型理论,计算了镁原子1s22s22p63snp 3P2,1,0(n=3～50) 和1s22s22p63sns 3S1 (n=4～50)里德堡系列的能级和量子亏损. 计算结果与已有的33个实验数据符合得很好,预言了136个能级的位置.     

在WBEPM理论中受扰里德堡能级研究

在最弱受约束电子势模型理论下,研究了外来微扰能级对里德堡能级系列的影响,给出了确定外来微扰能级位置的方法.依此计算了钡原子6snp(n≥15).P1和6snd(n≥9)3D3两个里德堡能级系列的量子数亏损和能级.计算结果和实验值的绝对误差在1 cm-1以内,达到了较高的精度.     

镁原子里德堡能级的计算

依据最弱受约束电子势模型理论，计算了镁原子1s22s22p63snp 3P2,1,0(n=3-50) 和1s22s22p63sns 3S1 (n=４-50)里德堡系列能级和量子亏损。计算结果与已有的33个实验数据符合得很好，预言了136个能级的位置。     

Positions and Widths of Anticrossings for Potassium Rydberg Stark States

The B-spline expansion technique is applied to study the anticrossings for potassium Rydberg states in a static electric field. The results of our calculation indicate that the antierossings are caused mainly by the core interaction or by the fine structure interaction. Our results for the positions and the widths of the anticrossings are in good agreement with experimental data.     

Characteristics of Level Anticrossing in Parallel Electric and Magnetic Fields

Using the matrix diagonalization method, we have studied two kinds of level anticrosing of Rydberg cesium atom in parallel electric and magnetic fields. Our numerical results reveal that in the vicinity position of level crossing between different parity states in a magnetic field, the energy levels and other behaviors of the states are quite sensitive to the electric field. We tabulate some features which may be as a guide in experimental verification.     

Trapping Rydberg atoms in an optical lattice

Rubidium Rydberg atoms are laser excited and subsequently trapped in a one-dimensional optical lattice (wavelength 1064 nm). Efficient trapping is achieved by a lattice inversion immediately after laser excitation using an electro-optic technique. The trapping efficiency is probed via analysis of the trap-induced shift of the two-photon microwave transition 50S→51S. The inversion technique allows us to reach a trapping efficiency of 90%. The dependence of the efficiency on the timing of the lattice inversion and on the trap laser power is studied. The dwell time of 50D(5/2) Rydberg atoms in the lattice is analyzed using lattice-induced photoionization.     

Energy levels of perturbed 6pnd J = 2 Rydberg states of Pb I by multichannel quantum defect theory

Energy levels of the odd-parity 6pnd J=2 Rydberg states of atomic lead are analyzed by the multichannel quantum defect theory (MQDT) with previous experimental energy levels. The 6pnd (6≤n ≤ 63) J=2 Rydberg energy levels are calculated and optimal MQDT parameters were obtained. Using these parameters, admixture coefficients for each level are calculated to designate the level denotations. The results show that strong channel mixings exist for the levels near the 6p6d (3/2)[5/2]2° and 6p6d (3/2)[3/2]2° pertubers. The five-channel model different from that in literature is used to predict 21 energy positions of 6pnd (1/2)[3/2]2° levels and to determine the denotations of all the 6pnd J=2 Rydberg states under 59788 cm-1 for Pb I.     

Narrow band gap group III-nitride alloys

Recent results on the properties of narrow gap group III-nitrides and their alloys are reviewed. It is shown that InN with the energy gap of 0.7 eV exhibits classical characteristics of a narrow gap semiconductor with strongly nonparabolic conduction band and an energy dependent electron effective mass. With the new discovery, the direct band gaps of the group III-nitride alloys span an extremely wide energy range from near infrared in InN to deep ultraviolet in AlN offering possibilities for new device applications of these materials. We also discuss properties of dilute group III-N–V alloys in which incorporation of a small amount of nitrogen results in a dramatic band gap reduction. All the unusual properties of the alloys are well described by a band anticrossing model that considers an interaction between localized nitrogen states and the extended states of the conduction band.     

铯原子nP_(3/2)(n=70—94)里德伯态的紫外单光子激发及量子亏损测量

基于成熟的光纤激光器、光纤放大器及高效激光频率转换技术,我们在实验中研制了一套瓦级输出的窄线宽连续波单频可调谐318.6 nm紫外激光系统,并在室温铯原子气室中实现了6S_(1/2)—nP_(3/2)(n=70—94)单光子跃迁里德伯激发.借助由铯原子6S_(1/2)(F=4)基态、6P_(3/2)(F′=5)激发态和nP_(3/2)(n=70—94)里德伯态构成的V型三能级系统,通过频率锁定于铯原子6S_(1/2)(F=4)—6P_(3/2)(F′=5)超精细跃迁的852.3 nm探测光束的吸收减弱信号获得了里德伯态的信息,并利用高精度波长计测量了铯原子nP_(3/2)(n=70—94)里德伯态的量子亏损值.经过与理论计算值的变化趋势进行对比,我们认为由于原子气室的里德伯屏蔽效应并不能完全屏蔽外部直流电场,铯原子气室内存在残余的直流电场,影响了对里德伯态的量子亏损值的实验测量.利用残余直流电场的Stark效应理论模型及其与有效主量子数n*的依赖关系,对铯原子里德伯态的量子亏损实验测量值进行了修正.修正后的铯原子nP_(3/2)(n=70—94)态量子亏损测量值为3.5591±0.0007,与理论计算值相吻合.     

Lattice dynamics study of low energy guest-host coupling in clathrate hydrate

Our lattice dynamics simulation of Xe-hydrate with four-site TIP4P oxygen-shell model can accurately reproduce each peak position in the inelastic incoherent neutron scattering spectrum at the acoustic band （below 15 meV） and yield correct relative intensity. Based on the results, the uncertain profile at ～6 meV is assigned to anharmonic guest modes coupled strongly to small cages. Blue shift is proposed in phonon dispersion sheet in the case of anticrossing and found to be an evident signal for guest-host coupling that explains the anomalous thermal conductivity of clathrate hydrate.     

Lattice dynamics study of low energy guest--host coupling in clathrate hydrate

Our lattice dynamics simulation of Xe-hydrate with four-site TIP4P oxygen-shell model can accurately reproduce each peak position in the inelastic incoherent neutron scattering spectrum at the acoustic band (below 15\,meV) and yield correct relative intensity. Based on the results, the uncertain profile at $\sim $6\,meV is assigned to anharmonic guest modes coupled strongly to small cages. Blue shift is proposed in phonon dispersion sheet in the case of anticrossing and found to be an evident signal for guest--host coupling that explains the anomalous thermal conductivity of clathrate hydrate.