Nuclear charge radius of 11Li

We have determined the nuclear charge radius of ¹¹Li by high-precision laser spectroscopy. The experiment was performed at the TRIUMF-ISAC facility where the ⁷Li-¹¹Li isotope shift (IS) was measured in the 2s→3s electronic transition using Doppler-free two-photon spectroscopy with a relative accuracy better than 10⁻⁵. The accuracy for the IS of the other lithium isotopes was also improved. IS’s are mainly caused by differences in nuclear mass, but changes in proton distribution also give small contributions. Comparing experimentally measured IS with advanced atomic calculation of purely mass-based shifts, including QED and relativistic effects, allows derivation of the nuclear charge radii. The radii are found to decrease monotonically from ⁶Li to ⁹Li, and then increase with ¹¹Li about 11% larger than ⁹Li. These results are a benchmark for the open question as to whether nuclear core excitation by halo neutrons is necessary to explain the large nuclear matter radius of ¹¹Li; thus, the results are compared with a number of nuclear structure models.     

Isotope shift of182Hg and an update of nuclear moments and charge radii in the isotope range181Hg-206Hg

The technique of collinear fast-beam laser spectroscopy has been used to measure the isotope shifts of the even-even isotopes of Hg (Z=80) in the mass range 182≤A≤198 at the on-line mass separator ISOLDE at CERN. The atomic transition studied (6s 6p ³ P ₂- 6s7s ³ S ₁,λ=546.1 nm) starts from a metastable state, which is populated in a quasi resonant charge transfer process. The resulting changes in nuclear mean square charge radii show clearly that¹⁸²Hg follows the trend of the heavier, even, weakly oblate isotopes. Correspondingly the huge odd-even shape staggering in the light Hg isotopes continues and the nuclear shape staggering and shape coexistence persists down to the last isotope investigated,¹⁸¹Hg. An update of isotope shift and hyperfine structure data for^181–206Hg is given, with a revised evaluation of the differences in nuclear mean square charge radii and of spectroscopic quadrupole moments.     

Isotope shift in Ni I and changes in mean-square nuclear charge radii of the stable Ni isotopes

The isotope shift in the Ni I spectrum was studied in 17 lines for all stable isotopes by means of a photoelectric recording Fabry-Perot spectrometer with digital data processing. The measured isotope shifts were separated into mass shift and field shift by comparing the optical isotope shift with model-independent δ〈r ²〉 values derived from a combined elastic electron scattering and muonic x-ray data analysis. The ratios of the observed field shifts in different types of transitions could be explained quantitatively by Hartree-Fock calculations. The relative changes in mean-square nuclear charge radii were found to be: [58, 60] 1.293(15); [60, 62]1; [62, 64] 0.641(16); [60, 61] 0.382(9). The absolute value δ〈r ²〉^60,62=0.170(35) fm² was derived using fine structure as well as hyperfine structure data for the determination of the change in the electron charge density at the nucleus in 4s-4p transitions.     

Laser-atomic-beam spectroscopy in Sm: Isotope shifts and changes in mean-square nuclear charge radii

A systematic investigation of the isotope shifts of all natural Samarium isotopes was performed in 15 lines of the Sm I spectrum using the laser-atomic-beam technique. The observed lines correspond to transitions between the ground configuration 4f ⁶6s ² and the upper configurations 4f ⁶6s6p and 4f ⁵5d6s ². In one line a contribution of hyperfine-structure second-order effects to the isotope shift of the odd isotopes could be demonstrated. The measured isotope shifts have been separated in all lines into field shift and mass shift contributions assuming the specific mass shift to be zero in pures ²-sp transitions. From the field shift of the pures ²-sp transitions the changes in mean-square nuclear charge radii, δ<r ²>, have been evaluated for all natural Sm isotopes (in fm²): [144, 148] 0.517(27); [148, 150] 0.303(16); [150, 152] 0.423(22); [152, 154] 0.230(12); [147, 148] 0.152(8); [148, 149] 0.092(5). There is good consistency with recent muonic x-ray measurements of the changes in the Barrett nuclear charge radii,δR _k , of the even Sm isotopes.     

Hyperfine structure and isotope shifts of neutron-rich138–146Cs

The 6s²S_1/2-7_p ²P_3/2 transition in^138–142Cs (λ=455.5 nm) has been investigated by high-resolution collinear laser spectroscopy in a fast atomic beam. The isotopes are obtained by on-line mass separation of fission products. Nuclear moments and changes of mean-square charge radii are derived from hyperfine structure and isotope shift.     

Hyperfine structure and isotope shift of the neutron-rich barium isotopes139–146Ba and148Ba

The hyperfme structure and isotope shift in the 6s ² S _1/2?6p ²P_3/2 line of Ba II (455.4 nm) have been measured by collinear fast-beam laser spectroscopy for the neutron-rich isotopes^139–146Ba and¹⁴⁸Ba. Nuclear moments and mean square charge radii of these isotopes have been recalculated. The isotope shift of the isotope¹⁴⁸Ba (T_1/2=0.64 s) could be studied for the first time, yieldingδ〈r²〉^138,148=1.245(3) fm².     

Nuclear moments and charge radii of107–111in determined by laser spectroscopy

Collinear fast beam laser spectroscopy has been used to measure the hyperfine structure and isotope shift in the atomic 5s ² 5p ² P _3/2-5s ² 6s ² S _1/2 transition (λ=451 nm) of^107–111In. Secondary beams of neutron deficient indium isotopes were prepared at the GSI on-line mass separator following fusion evaporation reactions. Magnetic dipole moments and electric quadrupole moments have been determined. The isotope shifts are discussed in terms of the change of the mean square nuclear charge radii and compared with the droplet model predictions and the deformation values calculated from the quadrupole moments.     

The electronic field shift factor of the 4s2S1/2−4p2PJ transitions in CaII

The isotope shifts (IS) of the resonance lines 4s²S_1/2–4p²P_Jin CaII (seven isotopes) have been measured by fast ion beam collinear laser spectroscopy (FIBCLS) with non-optical detection of the resonant laser-ion interaction. The electronic field shift factorF was derived from the experimental IS via a King plot procedure using the mean square nuclear charge radii from muon spectroscopy andelectron scattering. TheJ-independent resultF=–283(6) Mhz/fm² was obtained. TheF-value resulting from extensive many body perturbation theory (MBPT) calculations, recently performed by Märtensson-Pendrill et al., is in excellent agreement with the experimental value, confirming the reliability of the MBPT procedure.     

Nuclear moments and change in the charge-radii of neutron deficient lead isotopes

The nuclear moments of¹⁹⁵Pb and the change in the charge radii of^{192,194,195,196}Pb have been determined from the isotope shift and hyperfine structure of the 723 nm line of neutral lead by collinear laser spectroscopy.     

On the Yrast levels of106–108Sn

The isotope shift in the Ca-intercombination line withλ=6,573 Å was measured for all isotopes between⁴⁰Ca and⁴⁸Ca with the only exception of 47Ca. The combination of the results with muonic x-ray data yields highly accurate values for the changes of the mean square nuclear charge radii. In addition, the nuclear quadrupole moments of the three isotopes⁴¹Ca,⁴³Ca and⁴⁵Ca have been determined from the hyperfine structure splitting of the 4s 4p ³ P ₁ state.     

不稳定锂同位素移位的高精度测量实验方案(英文)

对丰中子晕核11Li的核电荷均方根半径的实验确定 ,特别是其与9Li的半径的差值 ,将对各种核模型进行灵敏的检验 .选择锂的合适跃迁 ,利用激光光谱技术高精度测量该跃迁的同位素移位 ,并扣除精确理论计算的质量移位贡献值 ,可以用来确定有关同位素的核电荷均方根半径 .就目前能够提供的实验设备和手段 ,对于不稳定锂的同位素8,9Li和短寿命丰中子晕核11Li而言 ,这是能够得到与核模型相独立的电荷半径值的唯一可行的方法 .这类实验正在德国重离子研究中心 (GSI)和欧洲核子中心的ISOLDE/CERN上计划实施 .描述了锂原子的激光激发共振电离途径和进行锂的同位素移位测量的实验装置,并讨论了采用这种方法测量到的6,7Li的初步结果及其精度 ,以及使用该方法研究不稳定核的灵敏性. A high-resolution isotope shift measurement of lithium isotopes in a suitable transition, combined with an accurate theoretical evaluation of the mass-shift contribution in the corresponding transition, can be used to determine the root-mean-square nuclear charge radii of these isotopes. For the unstable 8,9Li and the short-lived halo nucleus 11Li, this is the only approach available for obtaining nuclear-model-independent values of the charge radii within the reach of present-day facilities...     

Studies of light halo nuclei by the isotope shift method

Recent advances in atomic theory make possible the determination of nuclear charge radii for light isotopes from their isotope shift relative to other known isotopes. This method provides a unique measurement tool for the halo nuclei such as ⁶He and ¹¹Li. The theoretical techniques are reviewed and applied to recent measurements performed at Argonne, GSI, and TRIUMF.     

Nuclear charge radii and electromagnetic moments of scandium isotopes and isomers in the f7/2 shell

Collinear laser spectroscopy experiments on the ScII transition 3d4s ³D₂→3d4p ³F₃ at λ ≈ 363.1 nm were performed on the ^42–46Sc isotopic chain using an ion guide isotope separator with a cooler–buncher. Isotope and isomer shifts and hyperfine structures of five ground states and two isomers were measured. Preliminary results on the nuclear moments and charge radii changes deduced from these measurements are reported.     

Study of the neutron deficient 182–190Pb isotopes by simultaneous atomic- and nuclear-spectroscopy

Mean-square charge radii and magnetic moments have been measured for the neutron deficient lead isotopes, ^182–190Pb. The measurement was performed at the ISOLDE online mass separator, using the in-source resonance ionization spectroscopy technique. The wavelength of the first excitation step for the resonance ionization laser ion source (RILIS) was scanned over the resonance(s) whilst the α- and γ-ray spectra from the decay of the Pb isotopes were recorded as a function of the wavelength. The isotope shift and, in the case of odd-A isotopes, the hyperfine splitting were deduced. The rms-charge radii of the very neutron deficient Pb isotopes follow the smooth trend of the heavier isotopes. This finding indicates a spherical shape for the lead ground states at the neutron mid-shell (N = 104), where the excitation energy of the oblate 0⁺ state in the even isotopes reaches its minimum.     

Nuclear electromagnetic moments and charge radii of deformed thulium isotopes with the mass numbers A = 157−172

Hyperfine structures and isotope shifts of thulium isotopes in the mass range 157–172 have been measured in the atomic transitions 4f¹³6s²−4f¹²5d6s² (589.565 nm) and 6s²−6s6p (597.13 nm), using resonance ionization Spectroscopy at the IRIS facility. Nuclear magnetic dipole and electric quadrupole moments, and the changes in mean square charge radii have been obtained. They are analysed within the framework of the microscopic-macroscopic approach and the Hartree-Fock method, revealing single-particle and collective properties. Some conclusions on effective nucleon-nucleon interactions are drawn.     

光化学反应中氩气对激发态锂原子猝灭速率研究

本文对光化学法分离中氩气对2P激发态锂原子的碰撞猝灭速率进行研究.在弱激光作用下,通过对不同氩气压强下的锂原子蒸气吸收光谱和激发态锂原子的荧光发射光谱进行测量,得到氩气对2P激发态锂原子的猝灭速率常数为(12.29±0.92)×10-18m3·s-1.实验结果表明:在光化学锂同位素分离研究中,氩气对锂原子2P激发态的猝灭速率远小于2P激发态锂原子的自发辐射速率,碰撞猝灭效应对分离选择性的影响非常小,可以忽略不计.     

Isotope shift in molybdenum

The isotope shift in molybdenum has been studied in 16 lines of the arc and 6 lines of the spark spectrum for all stable isotopes by means of a photoelectric recording Fabry-Perot spectrometer with digital data processing. Mass shift and field shift were separated by two independent methods and were compared with the results of Hartree-Fock calculations. In the field shift large crossed-second-order effects ind ⁵ s ⁷ S and⁵ S were observed, which could be explained quantitatively by theory. The changes in mean square nuclear charge radii were evaluated from three 5s-5p transitions between different multiplets. The relativeδ〈r ² 〉 values are: [92, 94] 1; [94, 96] 0.854(3); [96, 98] 0.665(4); [98, 100] 1.003(5); [95, 97] 0.703(5);. [94, 95] 0.270(4); [96, 97] 0.119(5). The absolute values can be obtained withδ〈r ² 〉 ^{92, 94}=0.226(19)fm².     

Charge and mass radii of the tin isotopes

Data on the isotope shift of the nuclear charge densities of the tin isotopes and of their mean square charge radii are considered from the viewpoint of the Hartree-Fock and Droplet Models. Attention is paid to the electromagnetic corrections of order 1/m². Through a leptodermous analysis of charge and matter densities we find: (i) differences of m.s. charge radii are mainly sensitive to the external region, (ii) the electromagnetic corrections are important in that region, (iii) despite different leptodermous properties, forces Ska and GO-P lead to the same neutron skin thickness. The average rate of variation of the proton m.s. radius is interpreted as favouring either a low valueQ≈30 MeV for the droplet model asymmetry parameter, or a zero value for the saturation asymmetry parameterL.     

Isotope shifts in transitions between low-lying levels of Sr I by laser-atomic-beam spectroscopy

High-resolution laser-atomic-beam spectroscopy has been used to determine isotope shifts in five transitions between low-lying states of Sr I. With these results and existing data a parametric analysis of level isotope shifts has been performed. The transition isotope shifts have been separated into field shift and mass shift contributions with a King-plot procedure using model-independent nuclear charge equivalent radiiR _k from muonic x-ray measurements. Values for the mean-square nuclear charge radiiδ〈r ₂ 〉 have been calculated from the field shifts in the optical transitions 5s ^{2 1} S ₀-5s5p ³ P ₁ and 5s5p ³ P ₀-5s6s ³ S ₁ and compared with correspondingδ〈r ² 〉 values evaluated from muonic x-ray data.     

Nuclear spins,moments and charge radii of108−111Sn

The hyperfine structure splittings (hfs) and isotope shifts (IS) in the atomic transitions 5s ² 5p ^{2 1} S ₀ → 5s ² 5p6s ^1,3 P ₁ have been measured for the radioactive isotopes^108?111Sn and all stable ones. The tin isotopes were prepared as fast atomic beams for collinear laser spectroscopy at the GSI online mass separator following a fusion reaction. Nuclear spins, magnetic dipole, electric quadrupole moments and changes in mean square charge radii have been determined. In¹⁰⁹Sn the spinI=5/2 was measured for the nuclear ground state (T _1/2=18 min) in contradiction to the literature value. The mean square charge radii show a parabolic behaviour with a maximum at N=66. This is interpreted by collective effects, which are considerably stronger than accounted for by theB(E2)-values.