THEORETICAL INVESTIGATION OF THE ISOSPIN VIOLATING HADRONIC TRANSITIONS Ψ'→Ψ(11P1)+π° AND T"→T(11P1)+π°

The isospin violating processes Ψ'→Ψ(1¹P₁)+π° and T"→T(1¹P₁)+π° are investigated in the framework of the multipole expansion in quantum chromodynamics. Using the rate of Ψ'→Ψ+π° as an input to determine the isospin violating vertex, we obtain the following branching ratios for the processes BR(Ψ'→Ψ(1¹P₁)+π°)～10^-6-10^-5, BR(T"→T(1¹P₁)+π°)～10^-5-10^-3 for M₁1_p1=1/9(5M₁3_p2+3M₁3_p1+M₁3_p0). These are too small to be detected in the present experiments.     

ZBLAN玻璃中Pr3+掺杂离子3P0和1D2能级的发光特性和寿命

对ZBLAN氟锆酸盐玻璃中Pr³⁺掺杂离子³P₀和¹D₂能级的寿命和发光特性进行了较详细的光谱学研究。首先测量了两种掺杂浓度(质量分数分别为1×10^-3,5×10^-3)的Pr³⁺:ZBLAN玻璃的吸收光谱,然后运用时间分辨激光光谱技术测量了³P₀和¹D₂能级在激光单光子共振激发下的荧光发射谱和能级寿命。将不同荧光发射谱带的强度和文献报道的Judd Ofelt理论计算辐射跃迁几率数值做了比较分析,证明了文献中理论计算结果的可靠性。由于浓度猝灭效应,在相同的激发条件下,掺杂浓度为1×10^-3样品的荧光发射强度明显大于5×10^-3样品的荧光发射强度。但是从我们的测量结果看,掺杂浓度对³P₀和¹D₂ 的能级寿命值无显著影响。掺杂浓度为1×10^-3时,Pr³⁺离子³P₀和¹D₂能级的寿命值分别为46,322μ_s。     

The Hanle effect for the 3 S1/2 ↔ 3 P1/2 transition of sodium

Experimental results are reported for the Hanle effect on the 3 ²S_1/2 ↔ 3 ²P_1/2 transition of sodium at vapour densities between 10⁹ and 10¹² at/cm³.     

Optical pumping of the 2p3sP0 State of Ne (I = 3/2): g factor and metastability exchange cross section

A C.W. multi-mode dye laser is used to obtain by optical pumping an orientation of the 2p⁵ 3s³P₀ (F = 3/2) state of ²¹Ne. A magnetic resonance experiment leads to the measurement of the g factor g (³P₀) = 3.027 (8) × 10⁻⁴ to be compared with the theoretical prediction (3.025(6) × 10⁻⁴). One obtains also the metastability exchange cross section σ(³P₀) = 18.4 ± 4 Ų for collisions between metastable (³P₀) Ne atoms and ground state Ne atoms. This result is compared with other measurements and theoretical evaluation.     

Effects of relativity and “atomic structure” in the KLL Auger spectrum of Sr generated in the EC-decay of Y

The KLL Auger electron spectrum of ⁸⁸Sr generated in the EC-decay of ⁸⁸Y has been analyzed at the instrumental resolution of 11 eV using a combined electrostatic spectrometer. Energies and relative intensities of the all nine transitions were determined and compared with theoretical predictions. Our value of 12067.3(12) eV measured for the absolute energy of the dominant KL₂L₃(¹D₂) transition was found to be higher by 7.4 eV (i.e., more than 3σ) than that one obtained in a measurement with external excitation. The discrepancy indicates substantial influence of the “atomic structure effect” on absolute transition energies in our experiment. Very good agreement of the measured 0.14(3) and predicted 0.12 values for the KL₁L₂(³P₀/¹P₁) Auger transition intensity ratio clearly proved the predicted strong influence of the relativistic effects on the KL₁L₂(³P₀) transition rate even at Z = 38.     

新型电子俘获型光存储材料Sr2SnO4:Sb3+的发光性能研究

采用高温固相法在1300℃的温度获得了一种新型电子俘获型光存储材料 Sr₂SnO₄:Sb³⁺. 结果表明: 208 nm (Sb³⁺ 的¹S₀→¹P₁)和265 nm (¹S₀→³P₁)的紫外光是Sr₂SnO₄:Sb³⁺ 的最有效信息写入光源; 其发射是覆盖400---700 nm的宽带(³P_0,1→^XXS₀), 肉眼可看到淡黄色白光, 色坐标为(0.341, 0.395). 热释光谱研究结果表明: Sr₂SnO₄:Sb³⁺ 有分别位于39℃, 124℃, 193℃和310℃的四个热释峰. 其中, 39~℃的热释峰强度很低, 因而Sr₂SnO₄:Sb³⁺ 只具有不到140 s的微弱余辉. 而310℃的高温热释峰在空置1天后, 仍能保持约45.6%的初始强度, 并对980 nm的红外光有很好的红外上转换光激励响应. 因此, Sr₂SnO₄:Sb³⁺ 是一种具有一定的信息存储应用潜力的新型光存储发光材料.     

AlH~+离子5个Λ-S态和10个?态的光谱性质以及激光冷却的理论研究

利用考虑Davidson修正的内收缩多参考组态相互作用(icMRCI+Q)方法结合相关一致基组aug-ccpV6Z计算了AlH~+离子前两个离解极限对应的5个Λ-S态和10个?态的势能曲线.为了提高势能曲线的可靠性和精确性,计算中考虑了自旋轨道耦合效应、芯电子价电子相关和标量相对论修正以及将势能外推至完全基组极限.基于得到的势能曲线,获得了束缚和准束缚的4个Λ-S态和8个?态的光谱常数和振动能级,与已有的实验结果符合.计算了2(1/2)→X~2Σ_(1/2)~+和A~2Π_(3/2)→X~2Σ_(1/2)~+跃迁的跃迁偶极距.利用计算的精确的势能曲线和跃迁偶极矩,获得了2(1/2)~(第一势阱)(υ′=0, 1)→X~2Σ_(1/2)~+(υ′′)和A~2Π_(3/2)(υ′=0, 1)→X~2Σ_(1/2)~+(υ′′)跃迁的高度对角化分布的Franck-Condon因子(f_(00)和f_(11))和大的振动分支比;预测了2(1/2)~(第一势阱)(υ′=0, 1)和A~2Π_(3/2)(υ′=0, 1)态短的自发辐射寿命和窄的辐射宽度,这适合于AlH~+离子的快速激光致冷.所需的3束激光冷却波长都在紫外区域.这些结果表明了激光冷却AlH~+离子的可行性.此外,评估了自旋轨道耦合效应对光谱常数、振动能级和激光冷却AlH~+离子的影响.     

小型化锶光钟物理系统的研制

光钟物理系统的小型化是制约可搬运光钟及空间冷原子光钟发展的重要因素.主要介绍了小型化锶原子光钟物理系统的研制实验.采用真空腔内置反亥姆霍兹线圈,构建一个小电流、低功耗及小体积的磁光阱.实验中测得真空线圈通电电流仅为2 A时,磁光阱中心区域轴向磁场梯度可达到43 Gs/cm,完全满足锶原子多普勒冷却与俘获对磁场梯度的要求.目前已经成功将锶原子光钟物理系统体积缩小至60 cm×20 cm×15 cm,约为实验室原锶光钟物理系统体积的1/10,并且实现了锶原子的一级冷却,测得俘获区冷原子团的直径为1.5 mm,温度约为10.6 mK.锶同位素~(88)Sr和~(87)Sr的冷原子数目分别为1.6×10~6和1.5×10~5.重抽运激光707和679 nm的加入,消除了冷原子在~3P_2和~3P_0两能态上的堆积,最终可将冷原子数目提高5倍以上.     

State selective laser photodissociation of Tl2 at 337.1 nm by optogalvanic spectroscopy

This paper reports the first time achievement of laser photolysis of thallium dimers by single photon absorption of N₂-laser light at 337.1 nm resulting in a large population inversion of thallium 7 ²S excited state with respect to 6 ²P state. The photodissociation nitrogen laser pulse is spatially and temporally overlapped with the tunable dye laser pulse that is used for confirming the production of selectively excited thallium atoms. The dye laser excites the thallium atoms from 7 ²S state to high lying Rydberg states that collisionally ionize giving an ion-current signal which is subsequently processed by a box-car average/integrator and recorded on the chart recorder. The photodissociation of Tl₂ to Tl(7 ²S ) state demonstrates the existence of the molecular dissociative state 1g that is correlated with Tl 7 ²S +6 ²P states. A complete absence of 6 ²P state population among the photolysis products indicates a 100% prompt population inversion between 7 ²S and 6 ²P atomic states.     

Investigation of the HFS in the 4d 5p zP3,4 states of Mo and Mo by levelcrossing spectroscopy

The hyperfine structures of the z⁷P₃ and z⁷P₄ states of ⁹⁵Mo and ⁹⁷Mo have been investigated by levelcrossing spectroscopy. A fit of the experimental signal curves yields the magnetic and electric hfs coupling constants: ⁹⁵Mo z⁷P₃ |A| = 86.19(10) MHz, |B|=5.2(30) MHz, A/B0⁹⁵Mo z⁷P₄ |A|=64.05(30) MHz, |B|=4.3(30) MHz, A/B<0; ⁹⁷Mo z⁷P₃|A|= 88.0(1) MHz, |B|=60.0(20) MHz, A/B<0; ⁹⁷Mo z⁷P₄ |A|=65.4(3) MHz, |B|=50.0(50) MHz, A/B0. For the ratio of the electric quadrupole moments we fine ⁹⁷Q/⁹⁵ Q= -11.5(70).     

低速~(84)Kr~(15+,17+)离子轰击GaAs单晶

用345 keV的Kr15+和340 keV的Kr17+离子以45fi角入射n型GaAs单晶(100)面,测量了表面形貌的变化和发射的375—500 nm Ga I和Kr II的特征光谱线.Krq+(q=15,17)离子轰击后表面形貌的变化主要取决于入射离子的电荷态q.离子沉积到靶表面的能量引起Ga原子激发,其辐射光谱为Ga I 403.2 nm和Ga I 417.0 nm.入射离子中性化过程中俘获GaAs导带电子形成高激发态原子,通过级联退激填充3p,4d等空穴,P壳层电子跃迁发射谱线为Kr II 410.0 nm,Kr II 430.4 nm,Kr II 434.0 nm和Kr II 486.0 nm,Kr II486.0 nm为较强谱线.实验结果表明,入射离子与GaAs单晶相互作用发射的可见光产额与入射离子的电荷态密切相关,较高电荷态Kr17+离子入射产生的光辐射产额大约为Kr15+离子的两倍.     

锶原子互组跃迁谱的实验研究

观测了热原子束中锶原子(5s²)¹S₀—(5s5p)³P₁ 互组跃迁的荧光谱和饱和荧光谱, 实验测定了不同的参量下 ⁸⁸Sr(5s²)¹S₀—(5s5p)³P₁ 互组跃迁荧光谱. 研究结果表明: 不同的实验参数(温度、激光光强、激光扫描频率)对谱线有较大的影响, (5s5p)³P₁态的长寿命特点导致谱线强度随激光扫描频率呈倒数关系变化; 由于Doppler增宽, 渡越增宽等因素的影响, 谱线线宽远大于其自然线宽且随激光扫描频率呈正比关系变化.     

恒星氦燃烧关键反应12C(α,γ)16O天体物理S因子及其反应率

恒星氦燃烧阶段3α反应和12C（α,γ）16O反应相互竞争,两者的反应率共同决定了氦燃烧结束后12C与16O的丰度比,该比值是大质量恒星后继演化以及伴随的元素核合成过程的初始条件。目前,氦燃烧12C（α,γ）16O反应起始T₉=0.2处,天体物理模型要求的反应率的精确度要低于10%,然而尚未有实验或理论给出满足要求的结果。最为直接和可靠地获取12C（α,γ）16O反应率的方法,就是尽可能往低能区测量其天体物理S因子,然后通过理论外推到感兴趣的能区。为此基于经典的R-矩阵理论,建立了适用于低能核反应的多道、多能级的约化R-矩阵理论来拟合几乎所有可用的16O系统的实验数据。配合使用协方差统计和误差传播理论,拟合外推得到了客观的、内部自恰的和唯一性好的12C（α,γ）16O反应天体物理S因子。总的外推S因子STOT（0.3 MeV）=162.7±7.3 keV·b,理论上首次给出达到恒星演化与元素核合成模型的最低要求的S因子。基于计算给出的全能区的S因子,数值积分给出了温度位于0.04 6 T₉ 6 10的12C（α,γ）16O天体物理反应率。在T₉=0.2处,推荐的反应率为（7.83 ±0.35）×10-15 cm3mol-1s-1。During stellar helium burning, the rates of 3α and the 12C(α,γ)16O reaction, in competition with one another, determine the relative abundances of 12C and 16O in a massive star. The abundance ratio is the beginning condition of the following nucleosynthesis and star evolution of massive stars, which are extremely sensitive to the rate of 12C(α,γ)16O reaction at T₉=0.2. The most direct and trustworthy way to obtain the reaction rate of the 12C(α,γ)16O reaction is to measure the S factor for that reaction to as low energy as possible, and to extrapolate to energies of astrophysical interest. Based on a new multilevel and multichannel reduced R-matrix theory for applications in nuclear astrophysics, we have obtained an accurate and self-consistent astrophysical S factor of 12C(α,γ)16O, by a global fitting for almost all available experimental data of 16O system, with the coordination of covariance statistics and error-propagation theory. The extrapolated S factor of 12C(α,γ)16O was obtained with a recommended value STOT (0.3 MeV)=162.7±7.3 keV·b. And the reaction rates of 12C(α,γ)16O for stellar temperatures between 0.04 6 T₉ 6 10 are provided. At T₉=0.2, the reaction rate is (7.83 ±0.35)×10-15 cm3mol-1s-1, where stellar helium burning occurs.     

THE CONVERSION OF GLUONS INTO QUARKS AND THE MULTIQUARK STATES

The rate for the conversion of the gluon into a color octet quark pair which subsequently forms a multiquark state with another quark pair or a gluon is discussed. The static potential in a [(QQ)₈(qq)_8,1] state where Q=c,b and q=u, d is studied in the MIT bag model. It is shown that the repulsive Coulomb force between Q and Q is dominant at small QQ separations, which would significantly suppress the QQ wave function at the origin. For the charm quark (Q=c) the ratio of |Ψ(O)|² for the ordinary (QQ)₁ to that for the(QQ)₈ in the [(QQ)₈(qq)_8,1] state is estinated to be 2-5. Therefore the assumption |Ψ₈(O)|²=|Ψ₁(O)|² would lead to an overestimation for the rate of g*→QQ and it is necessary to take the suppression effect of the repulsive Coulomb force into consideration.     

THE 82S1/2→62D EXCITATION TRANSFER OF RUBIDIUM ATOMS INDUCED BY COLLISIONS WITH GROUND-STATE RUBIDIUM AND HYDROGEN MOLECULES

The processes of excitation transfer from the 8²S_1/2 state to the 6²D state of rubidium in Rb(8²S_1/2)-Rb(5²S_1/2) and Rb(8²S_1/2)-H₂ collisions have been studied experimentally. During irradiating the Rb vapor, mixed with H₂, by two light beams for selective stepwise excitation, the Rb 8²S_1/2→5²P_3/2 direct fluorescence and the Rb 6²D_3/2→5²P_1/2 sensitized fluorescence have been measured as a function of H₂ gas pressure. The measurements yielded the cross-sections σ(8²S_1/2→6²D) and σ^*(8²S_1/2→6²D) of Rb 8²S_1/2→6²D excitation tranfer induced by collisions with 5²S_1/2 atom and H₂ molecules respectively. The results are discussed in detail.     

真空紫外区Ar的高次离化光谱的研究

本文报道了波长在2000—194?真空紫外区域内Ar的高次离化光谱工作。观察到相当数量的新谱线,并归属了其中64条,还找到六个新能级,即:ArIV 3s²3p²(³P)3d²F_5/2,7/2, ArIV 3s²3p²(¹D)3d²S_1/2, ArV3s²3p3d关键词：     

Laser frequency locking based on the normal and abnormal saturated absorption spectroscopy of ~(87)Rb

We present a practical method to avoid the mis-locking phenomenon in the saturated-absorption-spectrum laserfrequency-locking system and set up a simple theoretical model to explain the abnormal saturated absorption spectrum. The method uses the normal and abnormal saturated absorption spectra of the same transition 5~2S_(1/2), F = 2–5~2P_(3/2), F'= 3 saturated absorption of the ~(87)Rb D_2resonance line. After subtracting these two signals with the help of electronics, we can obtain a spectrum with a single peak to lock the laser. In our experiment, we use the normal and inverse signals of the transitions 5~2S_(1/2), F = 2–5~2P_(3/2), F'= 3 saturated absorption of the ~(87)Rb D_2 resonance line to lock a 780-nm distributed feedback(DFB) diode laser. This method improves the long-term locking performance and is suitable for other kinds of diode lasers.     

The K-, L- and M-Auger and L-Coster-Kronig spectra of platinum

The K-, L- and M-Auger and L-Coster-Kronig spectra of platinum in the electron capture decay of ¹⁹⁵Au was measured by means of the Vanderbilt iron-free, double-focussing spectrometer. The energies and relative intensities of 55 peaks were measured in the L-Auger spectrum in the energy range of 5 to 12 keV. The intensities are compared to those calculated theoretically for silver by Asaad. The total L-Coster-Kronig plus M-Auger intensity (0 to 3.25 keV) was measured relative to the L-Auger intensity. The measured relative intensities of the KLL Auger lines are compared to the theoretical and experimental results of others. The measured KLL energies agree with those calculated semi-theoretically by Hörnfeldt and by Listengarten. A value of KLX/KLL = 0.548±0.044 was measured. A measurement of the KL₃L₃(³P₀)/KL₃L₃(³P₀+³P₂) ratio, the first reported in this Z-region, gave a value of 0.095±0.024.     

氦原子2~3S—2~3P精密光谱研究

氦原子是最基本的多电子原子,其精密谱是十分理想的检验多电子量子电动力学计算的平台,同时也是利用原子能级结构测定精细结构常数α的理想体系,还能获得原子核结构信息.本文结合我们团队的工作,综述基于氦原子的少体原子精密光谱研究.其中,主要包括氦原子2~3P_J精细结构分裂,以及2~3S—2~3P跃迁频率测定等研究,并对相关工作的前景进行了展望.     

Crystal growth,spectral properties and Judd–Ofelt analysis of Pr: CaF_2-YF_3

The 0.6 at.% Pr~(3+)-doped CaF_2-YF_3 crystal was successfully grown by the temperature gradient technique(TGT).X-ray diffraction analysis showed that the grown crystal still had cubic structure. The absorption spectrum, emission spectrum, Judd–Ofelt analysis and fluorescence decay curve at room temperature were discussed. The fluorescence lifetime of Pr: CaF_2-YF_3 crystal was 45.46 μs, and the σem ·τ of ~3P_0→~3H_6 and ~3P_0→~3F_2 transitions were calculated to be 80.92 × 10~(-20) cm~2·μs and 388.7 × 10~(-20) cm~2·μs, respectively. The FWHMs are 20.1 nm and 6.8 nm, which are higher than those of Pr: LiYF_4, Pr:LiLuF_4, Pr: LiGdF_4 and Pr: BaY_2F_8 crystals. The results show that the Pr: CaF_2-YF_3 crystal is expected to achieve 605 nm orange light and 642 nm red light laser operation.