高电离态Ti原子EUV光谱的实验研究

在中国原子能研究院HI-13串列加速器上用束-箔技术完成了80 MeV Ti离子和C箔相互作用产生的高电离态离子谱观测,与用激光等离子体技术的实验结果做了比较，大多数谱线与激光等离子体技术的实验结果有较好的符合，有3条谱线是未观测到的.这几条谱线为ⅩⅧ 13.406，ⅩⅧ 14.987，17.439nm, 属于2s2p^{2 4}P_3/2—2p^{3 2}D_3/2, 2s2p^{2 1}S₀—2sp^{3 1}P₁, 4p ¹P₀—5d ¹P₁跃迁. 关键词： 串列加速器 高电荷态原子 激发光谱     

Rh XⅢ—Cd XVI离子4s24p3—4s4p4能级与跃迁的理论计算

用HFR（Hartree-Fock with relativistic corrections）方法对Rb V—Cd XVI离子4s²4p³和4s4p⁴组态能级结构做了全面系统的理论计算研究. 通过分析能级结构参数的HFR理论计算值与基于实验能级拟合得到的计算值之比值随着原子序数Z_c变化的规律,运用广义拟合外推方法预言了这些离子能级结构参数. 由此进一步计算了Rh XⅢ,Pd XIV,Ag XV和Cd XVI离子4s²4p³（⁴S_3/2,²P_1/2,3/2,²D_3/2,5/2）和4s4p⁴（⁴P_1/2,3/2,5/2,²P_1/2,3/2,²D_3/2,5/2,²S_1/2）组态能级以及电偶极跃迁波长与振子强度. 研究表明,对于4s²4p³组态,单组态近似可以得到较满意的结果;而对于4s4p⁴组态,只有在考虑了4s²4p²4d的组态相互作用效应时,计算结果的准确性才能明显得到提高. 同时,本文还运用全相对论grasp2K-DEV程序包计算了Rh XⅢ—Cd XVI离子组态能级. 对于Rh XⅢ离子4s²4p³（²P_1/2）,Pd XIV离子4s²4p³（⁴S_3/2,²P_1/2,3/2,²D_3/2,5/2）和4s4p⁴（²P_1/2,3/2,²D_3/2,5/2,²S_1/2）,能级均无实验值;对于Ag XV和Cd XVI离子,截至目前还没实验能级数据,没有实验能级值的所有数据均仅来自本文的计算数值. 本文计算结果与已有实验值吻合得很好.     

中性硅3s23P2 3P2,1D2→3s3p3 3D3o跃迁能量,超精细结构常数与同位素移动的MCDHF计算

本文使用多组态Dirac-Hartree-Fock方法计算了²⁹Si的3s²3p^{2 3}P₂,¹D₂→3s3p³D₃⁰跃迁能量和³P₂,³D₃⁰超精细结构A常数以及Si同位素²⁹Si,³⁰Si和³¹Si相对于²⁸Si在3s²3p^{2 3}P₂→3s3p^{3 3}D₃⁰跃迁的同位素移动.通过尝试双电子激发（SD）和三电子激发（SDT）,分别考虑VV相关,CV相关和CC相关产生各种不同的扩展组态波函数得到的计算结果和实验值的比较,推测了对于中性硅原子这两个组态,内壳层2p2s,1s电子活动到外壳层的概率较小,而3s3p壳层中的电子都比较活跃,但主要是在n=3,4的壳层内活动,活动到更高n壳层的概率则比较小.     

Ga原子4s~24p及4s~25s态的超精细结构常数

基于相对论多组态Dirac-Fock（MCDF）方法的GRASP2K程序,通过系统的考虑电子关联效应和相对论效应,详细计算了⁷¹Ga原子的基态4s²4p²P_1/2、亚稳态4s²4p²P_3/2及激发态4s⁵s²S_1/2的超精细结构常数.结果表明原子实的极化效应对超精细结构常数起到了重要作用.     

243—263nm S原子Rydberg态的(2+1)共振增强多光子电离

在243—263nm波长范围,测量了S⁺分质量激发谱,得到SO₂分子光解产生的S原子近50条(2+1)共振增强多光子电离谱线．除了来自S原子基态3p⁴³P_2,1,0直至n=10的Rydberg态³P,³D,³F的许多双光子跃迁谱线外,观察到若干新的¹P⁰,⁵S^关键词：     

CALCULATION OF THE FINE STRUCTURE OF OXYGEN-LIKE IONS USING THE POLARIZATION POTENTIAL FUNCTION

We have calculated the forbidden transition energies and magnetic dipole transition probabilities of 2s²2p⁴(³P₁－³P₂) and 2s²2p⁴ (³P₀－³P₁) of oxygen-like isoelectronic sequences (Z=10－32) by a method of polarization potential correction. The transition energies show good agreement with experiment and are much better than the calculations in the literature. These results also illustrate that it is feasible to use the dipole expansion of the polarization potential to deal with some dynamic and non-dynamic effects in the central field approach. The relation of polarizability and cut-off radius with atomic number is discussed. We also give the fitted formula between the polarizability α₁ and atomic number Z as α₁=0.73429-9.56644×10^-4Z+7.43016×10^-5Z^{2-2.53298×10-6Z3+2.08306×10-8Z4.}     

一价铝离子能级结构的多通道量子亏损理论分析

利用多通道量子亏损理论(MQDT)对一价铝离子(AIII)的各受干扰序列:3sns ¹S₀,3snp ³P_0,1,2^O,¹P₁^O,3snd ¹D₂和3snf³F_2,3,4^O的能级结构进行理论分析。结果表明:前两个序列所受到的干扰较弱,后三个序列则受到了来自干扰态3p4s ¹P₁^O,3p^{2 1}D₂和3p3d³F_2,3,4^O的强烈干扰,而3snf ¹F₃^O序列则受到来自电离限上方干扰态的影响。利用获得的MQDT参数推算出3p3d ¹F₃^O干扰态位于电离限上方5613cm^-1处,这一结果与其他作者的预言相符合。 关键词：     

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。     

单电荷态钡离子超精细结构光谱

采用共线快离子束激光光谱学方法研究了钡离子亚稳态5d²D_3/2和激发态6p²P_3/2的超精细结构,并定出了相应的超精细结构常数. 关键词：     

Gd3+,Yb3+和Tm3+共掺杂氟化物纳米晶中Yb3+-Tm3+-Gd3+间的能量传递

用水热法合成了Y_0.8-x-yF₃∶Gd_x³⁺,Yb_0.2³⁺,Tm_y³⁺纳米晶的上转换发光材料。在典型的Y_0.595F₃∶Gd_0.200³⁺,Yb_0.200³⁺, Tm_0.005³⁺纳米微晶中,在980 nm激光激发下,观察到了Tm³⁺的紫外、紫色上转换发射明显增强和来自于Gd³⁺的⁶D_9/2、⁶I_J、⁶P_5/2及⁶P_7/2能级到基态⁸S_7/2能级的紫外发射。通过比较Y_0.8-x-yF₃∶Gd_x³⁺ ,Yb_0.2³⁺,Tm_y³⁺纳米晶样品的上转换发光性质以及Tm³⁺和Gd³⁺中一些激发态的能级寿命,借助于能级图描述了Yb³⁺-Tm³⁺-Ga³⁺之间的有效的能量传递过程。     

Lifetime of metastable magnesium atoms in superfluid helium

The metastable 3s3p³P_{0, 1, 2} states of the magnesium atom immersed into superfluid helium have been investigated. Absorption-fluorescence measurements were carried out to monitor the population of the³P₀,³P₁ and³P₂ level as a function of time. The population of these levels was found to decrease exponentially with a constant of =15±2 ms. This is about three times as long as the vacuum lifetime of the³P₁ level. In the resonant excitation band of the 3s3p³P states to the 3s4s³S state a blueshift of 70 nm compared to the emission and a large broadening were detected. The³P₂ and³P₀ states are not at all metastable any more. Additionally the weak intercombination transition of the³P₁ state to the¹S₀ ground state was investigated by monitoring this emission line as a function of time and of wavelength. The experiments resulted in the same exponential decay time as the excitation measurement. This outcome indicates a rather effective fine structure mixing of the considered Mg states in superfluid helium. Moreover, this raises the question whether common atomic quantum numbers are conserved and the selection rules are still valid.     

Formation of ultracold RbCs molecules by photoassociation

The formation of ultracold metastable RbCs molecules is observed in a double species magneto-optical trap through photoassociation below the ⁸⁵Rb(5S_1/2) + ¹³³Cs(6P_3/2) dissociation limit followed by spontaneous emission. The molecules are detected by resonance enhanced two-photon ionization. Using accurate quantum chemistry calculations of the potential energy curves and transition dipole moment, we interpret the observed photoassociation process as occurring at short internuclear distance, in contrast with most previous cold atom photoassociation studies. The vibrational levels excited by photoassociation belong to the 5th 0⁺ or the 4th 0^? electronic states correlated to the Rb(5P_{1/2, 3/2}) + Cs(6S_1/2) dissociation limit. The computed vibrational distribution of the produced molecules shows that they are stabilized in deeply bound vibrational states of the lowest triplet state. We also predict that a noticeable fraction of molecules is produced in the lowest level of the electronic ground state.     

Impact broadening and shift rates for the 6p2 3PJ′ → 7s 3P J o transitions of lead induced by collisions with argon and helium

The collisional broadening and shift rate coefficients of the 283.39 nm (6p ^{2 3}P₀ → 7s ³P₁ ^o ), 364.06 nm (6p ^{2 3}P₁ → 7s ³P₁ ^o ), 368.45 nm (6p ^{2 3}P₁ → 7s ³P₀ ^o ) and 405.90 nm (6p ^{2 3}P₂ → 7s ³P₁ ^o ) Pb lines by He and Ar have been measured by fitting the experimental absorption line shapes to theoretical Voigt profiles. The absorption measurements were performed in a resistively heated, Pb loaded oven with an integrated dc noble gas discharge to produce also Pb atoms in the 6p ^{2 3}P¹ and 6p ^{2 3}P² metastable states. The diffusion of the metastable atoms out of the discharge zone into the neutral noble-gas atmosphere enabled the line-shape and shift measurement of the lines involving the metastable states without the influence of the discharge plasma.     

Orientation of Cs 6p 2P3/2 atomic photofragments in a magnetic field: interference in the photodissociation of diatomic molecules

In a magnetic field, Cs₂ molecules were excited from the ground X¹Σ⁺_g(v_X=0,J_X=55) level to the D ¹Σ⁺_u(v=46,J=54) level by dissociation laser light linearly polarized parallel to the field, for which the magnetic sublevels were degenerated and thus all the transitions between them were simultaneously stimulated. Probe laser light excited the dissociated Cs 6p²P_3/2 atomic fragments to 6p²D_3/2 level and the resultant 6p²P_1/2 - 6d²D_3/2 emission was detected as the function of the wavelength of the probe light. The populations of the 6p²P_3/2,mj magnetic sublevels were determined from the relative strengths of the 6p²P_3/2,mj - 6d²D_3/2,m'j transitions induced by the probe light. Non-zero orientation O₀ was found in the ensemble of dissociated Cs 6p²P_3/2 atomic fragments. The orientation O₀ increased as the magnetic field strength increased. It was demonstrated both experimentally and theoretically that the orientation O₀ was induced through the interference in the excitation and dissociation paths in the presence of an external magnetic field, even when all degenerated transitions between the magnetic sublevels of the molecules are simultaneously excited by the light linearly polarized parallel to the field.     

Isotope separation by laser deflection of an atomic beam

Separation of isotopes of barium has been accomplished by laser deflection of a single isotopic component of an atomic beam. With a tunable narrow linewidth dye laser, small differences in absorption frequency of different barium isotopes on the 6s^{2 1}S₀₋ 6s6p¹P₁ 5536 Å resonance were exploited to deflect atoms of a single isotopic component of an atomic beam through an angle large enough to physically separate them from the atomic beam. It is shown that the principal limitation on separation efficiency, the fraction of the desired isotopic component which can be separated, is determined by the branching ratio from the excited state into metastable states. In barium, repeated absorptions and emissions on the 5536 Å transition eventually result in decay from the 6s6p¹P₁ state to the metastable 6s5d¹D₂ state. This was observed to occur for all but 3% of the¹³⁸Ba atoms. As a result, the efficiency of separation was about 0.7 for the 8 mrad atomic beam divergence employed. (Throughput was nearly 1 mg/day. No attempt was made to maximize this value.) The isotopic purity of the separated atoms was measured to be in excess of 0.9, limited only by instrumental uncertainty. The effects of near resonant atomic scattering and excitation exchange on isotopic purity are considered. Work performed under the auspices of the U.S. Energy Research & Development Administration.     

Enhanced blue-green-red up-conversion and 1.3-μm emission of Pr/Yb-codoped oxyhalide tellurite glasses with PbCl2 doping

We report on the blue-green-red up-conversion spectroscopic properties of Pr³⁺/Yb³⁺-codoped oxyhalide tellurite glasses upon excitation of a conventional 980 nm laser diode (LD). Significant enhancement of the blue-green-red up-conversion emission intensity has been observed with increasing PbCl₂ doping. The up-conversion intensity has a quadratic dependence on incident pump laser power, indicating a two-photon process. The population of the Pr³⁺ upper ³P₀ emitting level was accomplished through a combination of a ground state absorption, energy transfer and excitated state absorption. 1.3-μm emission in the second telecom window originated from Pr³⁺:¹G₄→³H₅ transition has also been investigated upon excitation at 980 nm LD. The measured peak wavelength and full width at half-maximum of the fluorescent are 1335 nm and ∼100 nm, respectively. An enhanced 1.3μm emission with increasing PbCl₂ doping has also been observed. Codoping of Yb³⁺ significantly enhance both the blue-green-red up-conversion emission and 1.3-μm emission intensity by way of a nonradiative Yb³⁺:²F₅→Pr³⁺:¹G₄ energy transfer.     

Theoretical study of the 5p56s – 5p6 spectra of neutral xenon

Recent high precision measurements on the lifetime of the metastable 6s[3/2]₂ state of atomic xenon display a difference with previous predictions by a factor of 2–3. In the present work, a systematic relaxation and correlation approach, which has been developed on the basis of a widely used multi-configuration Dirac-Fock method, is applied to study the electric dipole allowed E1 and forbidden M1, E2 and M2 transitions between the 5p⁵ 6s and 5p⁶ configurations. We systematically include the correlation effects which arise from all the single and double excitations from the occupied shells into the (n=6–10) active sets and the relaxation effects caused by change of the electron density between the radiative initial- and final-states. This study not only reduces greatly the existing discrepancy in the lifetime of the 6s[3/2]₂ state, but also presents rather consistent results for both the lifetime of the metastable 6s'[1/2]₀ state and the oscillator strength of the 5p⁵ 6s - 5p⁶ E1 resonant transitions.     

Lifetime of metastable fluorine atoms

For laser collimation of neutral F atoms, a resonance transition cycle between the metastable and the upper excited states (3s⁴ P _5/2?3p⁴ D ⁰ _7/2) can be used as a two-level closed system. We have determined the lifetime of the metastable state (3s⁴ P _5/2) in F atoms by measuring the decay curve of the fluorescence intensity as a function of distance from the plasma source. Combining the measured velocity of F radicals from the Doppler shift of the fluorescence peak, we have obtained the lifetime of the F metastable state as 3.7±0.5 μs. With this short metastable lifetime of F radicals, the simple Doppler cooling method using spontaneous light force is not practical for laser collimation of F radicals. Use of stimulated light force may be necessary to collimate F radical beams in a short distance. Received: 4 July 2000 / Published online: 13 September 2000     

Multiconfiguration Dirac-Hartree-Fock calculations of transition rates and lifetimes of the eight lowest excited levels of radium

The multiconfiguration Dirac-Hartree-Fock (MCDHF) model has been employed to calculate the transition rates between the nine lowest levels of radium. The dominant rates were then used to evaluate the radiative lifetimes. The decay of the metastable 7s7p³P₀ state through 2-photon E1M1 and hyperfine induced channels is also studied.     

Lifetimes of some highly excited levels in the Pb-I spectrum measured by the hanle method

Natural lifetimes of some highly excited levels in the Pb-I spectrum have been measured by the zero field level crossing (Hanle) method. The levels were reached by optical excitation from the metastable 6p ^{2 3} P ₂ and 6p ^{2 3} P ₁ states, were a considerable population had been created by means of adc discharge in a Pb atomic beam. An atomic beam source producing atoms in metastable states is described. For the lifetimes τ of the investigated levels we find:τ(6p(1/2)6d ³ D ₁)=3.74(28) ns,τ(6p(1/2)6d ³ F ₂)=25.8(1.3) ns,τ(6p(1/2)6d ³ D ₂)=4.17_(?31) ^(?49) ns,τ(6p(1/2)6d ³ F ₃)=6.08(26) ns,τ(6p(3/2)7s)³ P ₂=5.85(27) ns. These results are compared with lifetimes derived from oscillator strengths given in the literature.