采用相对论多组态Dirac-Hartree-Fock方法对Mg原子同位素位移的理论研究

利用相对论多组态Dirac-Hartree-Fock方法研究了Mg原子基态到低激发态~1S_0-~1P_1和~1S_0-~3P_1两条跃迁谱线的同位素位移参数,包括正常质量位移系数,特殊质量位移系数和场位移因子,并计算了~(24)Mg,~(25)Mg和~(26)Mg三个稳定同位素的同位素位移.在计算中采用了一种受限制的双电子激发模式,并将同位素位移计算结果与已有的实验测量和理论计算结果进行了对比.结果表明,用本文的研究方法计算的Mg原子同位素位移与其他理论结果和实验测量值十分符合.本文的计算结果可以为~(20-40)Mg同位素位移测量实验提供必要的参考,所用的计算方法也可以应用到其他类Mg体系(核外电子数等于12的离子)等多电子离子的光谱结构计算和同位素位移的研究中.     

142—146,148,150Nd+同位素位移的共线快离子束激光光谱学实验研究

原子光谱中,同位素位移是少数几个能够将原子物理学和原子核物理学这两个不同的物理学分支联系起来的课题之一.本文利用共线快离子束激光光谱学方法,测量了正一价钕离子所有7个稳定同位素(A=142—146,148,150)之间的能量位移.与已有的结果比较,测量精度提高了一个数量级 关键词： 同位素位移 快离子束激光光谱学     

测量铀同位素位移光谱的方法和装置

测量铀同位素的高分辨位移光谱,目前多采用原子束光谱法[1].该方法的分辨率和准确度高,但是设备复杂昂贵,操作复杂,特别是很难避免铀的高温腐蚀和放射性污染.近年来,美国 Los Alamos实验室的R.A.Keller等人[2]提出用光电流光谱法测量铀同位素位移光谱,并采用天然铀空心阴极灯测量了238U-235U的位移光谱.但是该方法由于同位素丰度相差悬殊,丰度高的同位素谱线强,丰度低的谱线弱,严重影响测量的灵敏度与准确度.特别是使用的单光路测量系统还不能测量零位移光谱. 本发明的目的,在于改进光电流光谱法单光路系统测量铀同位素仕移光谱受同位素…     

用激光光电流光谱法测量同位素位移

建立了用激光光电流光谱测量同位素位移的方法并测量了波长在５７８．２ｎｍ处铜的同位素位移，波工在５７６．２ｎｍ处铕的同位素位移以及波长在５７４．８ｎｍ处铀的同位素位移。     

~(142—146,148,150)Nd~ 同位素位移的共线快离子束激光光谱学实验研究

原子光谱中 ,同位素位移是少数几个能够将原子物理学和原子核物理学这两个不同的物理学分支联系起来的课题之一 .本文利用共线快离子束 激光光谱学方法 ,测量了正一价钕离子所有 7个稳定同位素 (A =142— 146 ,148,15 0 )之间的能量位移 .与已有的结果比较 ,测量精度提高了一个数量级     

原子光谱中同位素位移和超精细结构分裂

利用共线快离子束-激光光谱学方法测量了钕离子所有7个稳定同位素(A=142～146,148,150)之间的同位素位移和两个奇同位素(A=143,145)的超精细结构分裂．     

相对论多组态相互作用方法计算Mg~+离子同位素位移

采用相对论多组态相互作用方法研究了Mg~+离子3s~2S_(1/2)—3s~2P_(1/2)和3s~2S_(1/2)—3s~2P_(3/2)两条跃迁谱线的特殊质量位移系数和场位移因子,并计算了中子数8≤N≤20的Mg~+离子的同位素位移.计算结果与其他理论的计算值符合得比较好,与最新的实验测量结果比较,相对误差在0.13%到0.28%范围,是目前最接近Mg~+离子同位素位移实验测量的理论计算结果.该计算结果可为Mg~+离子同位素位移实验和理论研究提供参考,能够用于Mg~+离子的短寿命同位素的光谱测量实验以及利用Mg~+离子开展幻中子数N=8和N=20附近的奇异原子核特性研究等.所用的计算方法和电子激发模式也可以推广到其他核外电子数为11的多电子体系,用于开展相应的原子光谱结构计算和同位素位移的理论研究.     

使用自聚焦透镜测量小位移的新方法

提出一种使用自聚焦透镜构成的光强度调制的光学位移测量原理，利用发光二极管作光源，光从第一根自聚焦透镜发出，然后受到反射镜的反射而进入第二根自聚焦透镜，当反射镜有小位移时，进入第二根自聚焦透镜的光强度被调制，用光电管检测光强度的变化，可以确定位移的大小。根据该原理，位移分辨率的理论值可达１０＾－９ｍ，实验测量的位移分辨率为１０＾－８ｍ，该原理亦可用于测量小振动和压力等量。     

光栅衍射多普勒效应位移测量的理论分析和实验结果

本文研究了一种利用光栅衍射的多普勒效应进行位移测量的新方法.文中进行了光路结构和测量原理的理论分析,得出测量公式,证明了用光栅拾取多路差拍信号的相位关系.实验结果表明,它具有高的信号质量,可有效地用于位移的精密测量.     

氮原子同位素计算

本文利用多组态Dirac-Hartree-Fock和相对论组态相互作用的方法计算了氮原子的同位素¹⁴N和¹⁵N的四对能级跃迁：3s⁴P→3p⁴P°，3s⁴P→3p⁴D°，3s²D→5p²D°，和3s²P→3p²P°相应的特殊质量位移系数和场因子. 由计算所得的正常质量位移，特殊质量位移系数和场因子获得了氮原子同位素的正常质量位移、特殊质量位移和场位移. 同时将计算结果和报道的实验和理论计算结果进行了比较.     

Isotope shift measurements on the neutron-deficient thallium isotopes

Isotope shifts of the neutron-deficient thallium isotopes were measured on-line at the UNISOR mass separator. Spectroscopy was carried out using collinear fast beam laser spectroscopy in neutral thallium. The changes of the mean square charge radii were derived from the measurements. The changes in charge radii of the I=7 isotopes, including the newly measured¹⁸⁸Tl, are compared to the results in mercury and lead.     

Isotope shifts and hyperfine structure in calcium 4snp and 4snf F Rydberg states

Isotope shifts and hyperfine structure have been measured in 4snp ¹ P₁ and Rydberg states for all stable calcium isotopes and the radioisotope ⁴¹Ca using high-resolution laser spectroscopy. Triple-resonance excitation via Rydberg state was followed by photoionization with a CO₂ laser and mass selective ion detection. Isotope shifts for the even-mass isotopes have been analyzed to derive specific mass shift and field shift factors. The apparent isotope shifts for ⁴¹Ca and ⁴³Ca exhibit anomalous values that are n-dependent. This is interpreted in terms of hyperfine-induced fine-structure mixing, which becomes very pronounced when singlet-triplet fine-structure splitting is comparable to the hyperfine interaction energy. Measurements of fine-structure splittings for the predominant isotope ⁴⁰Ca have been used as input parameters for theoretical calculation of the perturbed hyperfine structure. Results obtained by diagonalizing the second-order hyperfine interaction matrices agree very well with experimentally observed spectra. These measurements allow the evaluation of highly selective and sensitive methods for the detection of the rare ⁴¹Ca isotope. Received 17 December 1999 and Received in final form 29 March 2000     

Hyperfine structure in the 6p5d configuration and isotope shifts in transitions between the 6s5d and the 6p5d configurations in Ba I

High-resolution laser fluorescence spectroscopy, using a single-mode dye laser acting on a collimated atomic beam, has been performed to determine the hyperfine-structure (hfs) constants in six states of the 6p 5d configuration of¹³⁵Ba and¹³⁷Ba. Isotope shifts (IS) for eleven transitions between the 6s 5d and the 6p 5d configurations have also been measured. From an analysis of the energy levels, intermediate angular wavefunctions have been deduced. The wavefunctions are used to evaluate experimental hyperfine parameters from the experimental hfs constants. The parameters are, for the magnetic-dipole interaction compared with theoretical values, and for the electricquadrupole interaction used to estimate the nuclear quadrupole moments for the odd isotopes. The IS in the measured transitions are analysed using a King-plot, with the first resonance line in Ba II as the reference. Specific mass and field shifts are evaluated for the measured transitions. The field shifts have been used to determine the change in mean-square radius between the natural abundant Ba-isotopes.     

Isotope shift measurements and charge radii of152–158Yb

Isotope shifts have been measured for the neutron deficient even Yb isotopes up to the neutron shell closure at N=82. The isotope shifts were measured using the 556-nm atomic resonance transition from the¹ S ₀ ground state to the³ P ₁ level. The heavier isotopes of Yb have been investigated by Buchinger et al./1/. The change in (r ²) observed for Yb isotopes with N=82–90 has considerably different behavior than for the lighter rare earths.     

Isotope and hyperfine splittings for two UV transitions in tungsten I by saturation and polarisation spectroscopy

Isotope shifts and hyperfine splittings in tungsten I have been measured by Doppler-free saturated absorption and polarisation spectroscopy on two UV transitions at 294.44 nm and 294.70 nm. The splittings between the even isotopes (¹⁸²W, ¹⁸⁴W, ¹⁸⁶W) and the splitting between the two strong hyperfine components of ¹⁸³W were measured in a natural isotopic mixture of tungsten introduced into a hollow cathode discharge. In addition, using single isotope ¹⁸³W, the level hyperfine splittings were measured by resolving crossover peaks between the strong and weak hyperfine components. These measured level splittings are compared with those predicted from centre of gravity considerations.     

Laser spectroscopy and mass measurements on alkali isotopes

Isotope shifts, spins, hyperfine structures and masses have been measured for the series of the alkali isotopes including the nuclei far from stability. The method of laser spectroscopy and its combinations with rf excitation are described. Some results are discussed, namely the first observation of the red doublet D₁-D₂ of francium, and the study of shell effects and changes of shape with mass and δ〈r ²〉 measurements for Rb and Na isotopes.     

Laser spectroscopy of the bismuth isotopes

Isotope shifts and hyperfine structures of the bismuth isotope chain have been studied on the 306.7 nm line in off-line measurements using gas cell laser spectroscopy and atomic beam spectroscopy. The changes in nuclear mean square charge radii and the nuclear magnetic and spectroscopic quadrupole moments have been deduced. The neutron-rich isotopes are the first isotones of Pb to be measured immediately above the N=126 shell closure. A remarkable correspondence between the nuclear charge radii of the Bi and Pb isotope chains is demonstrated by a King Plot analysis. The relationship between nuclear shapes and the charge radii can be understood in the framework of the spherical shell model using few-nucleon configurations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Subshell effect in mean square charge radii of stable even cadmium isotopes

Isotope shifts of the 467.8 nm line have been measured by Doppler-free saturation spectroscopy for the even Cd isotopes 106 through 116. The differential changes in mean square charge radii derived from the field shifts show a pronounced break in their trend atN=64, giving evidence for the closure of theg _7/2 neutron subshell. The average charge radii determined from our data and the rms radius of¹¹⁴Cd measured with muonic X-rays verify the general trend predicted by the droplet model but are off by about 35 mfm on an absolute scale. A consistent interpretation of δ〈r ²〉 further supports the necessity for considering changes in the skin thickness of the nuclear charge distribution.     

Laser isotope separation of titanium by two-step photoionization

Titanium isotopes were selectively excited and photoionized using a two-step photoionization method, and the isotope separation was demonstrated, in which a separation factor of around 15 for⁵⁰Ti was obtained. Spectroscopic parameters such as isotope shifts, photo-ionization cross section and excited state lifetimes were also measured. Isotope shifts up to 0.92 GHz were obtained for the transitions between 0 and 19938 cm^–1 or between 170 and 20006 cm^–1 among five isotopes. The cross section is 7.4×10^–17 cm² for the photo-ionization. The excited state lifetimes are 330±20 ns for 19938 cm^–1, 260±15 ns for 20006 cm^–1 and 250±15 ns for 20126 cm^–1.     

Electronic and nuclear properties from the analysis of the isotope shifts in the spectral lines of lead

Isotope shifts in the 623.7 nm line of Pb I have been measured. Then, in a spectral range of nm the optical isotope shifts in 24 lines of neutral and singly ionized lead have been analyzed using a combined model-independent method. From the combination of the optical isotope shifts data with elastic electron scattering, muonic X-ray and electronic K_α X-ray data, we were able to determine the two contributions to the total isotope shift, namely the mass and the field shifts, and to obtain the values of several nuclear factors for a long chain of lead isotopes.