Changes In Charge Radii Research Articles

Simple Nuclear Structure in (111-129)Cd from Atomic Isomer Shifts.

Isomer shifts have been determined in ^{111-129}Cd by high-resolution laser spectroscopy at CERN-ISOLDE. The corresponding mean square charge-radii changes, from the 1/2^{+} and the 3/2^{+} ground states to the 11/2^{-} isomers, have been found to follow a distinct parabolic dependence as a function of the atomic mass number. Since the isomers have been previously associated with simplicity due to the linear mass dependence of their quadrupole moments, the regularity of the isomer shifts suggests a higher order of symmetry affecting the ground states in addition. A comprehensive description assuming nuclear deformation is found to accurately reproduce the radii differences in conjunction with the known quadrupole moments. This intuitive interpretation is supported by covariant density functional theory.

Charge radii in modern macroscopic-microscopic mass models: The role of dynamic quadrupole deformation

We calculate the charge radii of nuclei in the frame of the finite-range droplet model including axial and reflection asymmetry. In addition, in order to empirically include dynamic contributions into the radius calculations, we use the quadrupole deformation \( \beta_{{2}}^{}\) deduced from the experimental B(E2;01+\( \rightarrow\) 21+) value as an input parameter. It is found that the calculated charge radii are in poor agreement with measured charge radii in the mass regions A 210 . A slight systematic deviation is observed for the difference between model predictions and experiment for 110 < A < 210 . However calculated changes of charge radii along isotope chains are in better agreement with the experimental data when \( \beta_{{2}}^{}\) ’s from B(E2;01+\( \rightarrow\) 21+) values are used instead of the model \( \beta_{{2}}^{}\) ’s.

Deformation change in light iridium nuclei from laser spectroscopy

Laser spectroscopy measurements have been performed on neutron-deficient and stable Ir isotopes using the COMPLIS experimental setup installed at ISOLDE-CERN. The radioactive Ir atoms were obtained from successive decays of a mass-separated Hg beam deposited onto a carbon substrate after deceleration to 1kV and subsequently laser desorbed. A three-color, two-step resonant scheme was used to selectively ionize the desorbed Ir atoms. The hyperfine structure (HFS) and isotope shift (IS) of the first transition of the ionization path 5d76s24F9/2 → 5d76s6p6F11/2 at 351.5nm were measured for 182-189Ir, 186Irm and the stable 191, 193Ir. The nuclear magnetic moments μI and the spectroscopic quadrupole moments Qs were obtained from the HFS spectra and the change of the mean square charge radii from the IS measurements. The sign of μI was experimentally determined for the first time for the masses 182≤A≤189 and the isomeric state 186Irm. The spectroscopic quadrupole moments of 182Ir and 183Ir were measured also for the first time. A large mean square charge radius change between 187Ir and 186Irg and between 186Irm and 186Irg was observed corresponding to a sudden increase in deformation: from β2 ≃ + 0.16 for the heavier group A = 193, 191, 189, 187 and 186m to β2≥ + 0.2 for the lighter group A = 186g, 185, 184, 183 and 182. These results were analyzed in the framework of a microscopic treatment of an axial rotor plus one or two quasiparticle(s). This sudden deformation change is associated with a change in the proton state that describes the odd-nuclei ground state or that participates in the coupling with the neutron in the odd-odd nuclei. This state is identified with the π3/2+[402] orbital for the heavier group and with the π1/2-[541] orbital stemming from the 1h9/2 spherical subshell for the lighter group. That last state seems to affect strongly the observed values of the nuclear moments.

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.

Nuclear Charge Radii ofLi9,11: The Influence of Halo Neutrons

The nuclear charge radius of 11Li has been determined for the first time by high-precision laser spectroscopy. On-line measurements at TRIUMF-ISAC yielded a 7Li-11Li isotope shift (IS) of 25 101.23(13) MHz for the Doppler-free [FORMULA: SEE TEXT]transition. IS accuracy for all other bound Li isotopes was also improved. Differences from calculated mass-based IS yield values for change in charge radius along the isotope chain. The charge radius decreases monotonically from 6Li to 9Li, and then increases from 2.217(35) to 2.467(37) fm for 11Li. This is compared to various models, and it is found that a combination of halo neutron correlation and intrinsic core excitation best reproduces the experimental results.

Lasers for nuclear physics

An overview is given on the application of lasers in nuclear physics. The review focuses on atomic physics techniques for extracting nuclear properties such as the nuclear spin, the magnetic dipole moment, the spectroscopic quadrupole moment, and changes in charge radii. References are given for the work carried out in this field since 1988. At that time, E.W. Otten prepared an extensive review with a complete compilation of data on properties of nuclear ground and isomeric states, obtained by optical spectroscopy on unstable nuclei.

Charge radius change in the heavy tin isotopes until A = 132 from laser spectroscopy

Laser spectroscopy measurements have been carried out on the very neutron-rich tin isotopes with the COMPLIS experimental setup. Using the 5s 25p 23P 0 → 5s 25p6s 3P 1 optical transition, hyperfine spectra of 126-132Sn and 125m, 127m, 129m-131mSn where recorded for the first time. The variation of the mean-square charge radius ( δ〈r 2〉) between these nuclei and nuclear moments of the isomers and the odd isotopes were thus measured. An odd-even staggering which inverts at A = 130 is clearly observed. This indicates a small appearance of a plateau on the δ〈r 2〉 which has to be confirmed by measuring the isotope shift beyond A = 132.

Nuclear moments of neutron deficient iridium isotopes from laser spectroscopy

Laser spectroscopy measurements have been performed on neutron deficient iridium isotopes. The hyperfine structure and isotope shift of the optical Ir I transition 5d76s24F9/2 → 5d76s6p 6F11/2 at 351.5 nm have been studied for the 182–189Ir, \(^{186} {\text{Ir}}^\user1{m} \) and 191,193Ir isotopes. The nuclear magnetic and quadrupole moments were obtained from the HFS measurements and the changes of the mean square charge radii from the IS measurements. A large mean square charge radius change between 187Ir and 186Ir and between \(^{186} {\text{Ir}}^\user1{m} \) and \(^{186} {\text{Ir}}^\user1{g} \) has been observed.

Deformation change between184mAu and184gAu

Isotope shift and hyperfine structure measurements have been performed on the short lived184Au nucleus using the COMPLIS apparatus installed at ISOLDE. The charge radius change and the magnetic and quadrupole moments of both isomeric and ground states have been deduced. The184Au ground state appears to be slightly more deformed than the isomeric state.

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.

Lasers at accelerators—past, present and future

The application of lasers at accelerators is reviewed with emphasis on laser spectroscopy of short-lived isotopes and the determination of nuclear spins, moments, and changes of charge radii in long isotopic chains leading far-off stability. Experimental techniques as well as future directions are discussed.

Nuclear charge radii changes of uranium and hafnium isotopes determined by laser spectroscopy

The present work reports measurements of isotope shifts and hyperfine structure in the optical spectra of two high-Z elements: Hf and U. The experiments are based on the observation of the resonance fluorescence in a well collimated atomic beam, excited by a tunable dye laser. The chains of the stable Hf isotopes and of233–236, 238U have been investigated and changes in ms nuclear charge radii have been deduced. The results have been discussed from the point of view of nuclear structure in the investigated regions.

Optical isotope shift and hyperfine structure measurements of 152,154-158,160Gd.

Laser spectroscopic measurement of the optical isotope shifts of all the naturally occurring Gd isotopes have been made using a collimated atomic beam system. The isotope shift and hyperfine splitting of all the stable isotopes have been measured for five optical transitions of Gd I at 570.135, 574.466, 574.636, 575.188, and 579.138 nm. The data were combined with the available muonic and electronic x-ray isotope shift data to extract the specific mass shift and the field shift constant. The change in charge radii, \ensuremath{\lambda}\ensuremath{\approxeq}\ensuremath{\delta}〈${\mathit{r}}^{2}$〉, have been extracted and compared with droplet model predictions. The accuracy of the isotope shift measurements is 0.1% and the extracted charge radius changes have an uncertainty of about 3%.

Changes of charge radii and hyperfine interactions of the Dy isotopes

A continuous wave dye laser and a thermal atomic beam were used to measure the optical isotope shifts and hyperfine splittings for the 5547 \AA{}, 5639 \AA{}, 5652 \AA{}, 5974 \AA{}, and the 5989 \AA{} transition of the seven stable isotopes of dysprosium. The hyperfine splitting of the odd-$A$ isotopes has been analyzed using the formalism of Sanders and Beck and the hyperfine anomaly has been extracted. Comparison with calculations using Nilsson wave functions is presented. The isotope shift measurements have been analyzed with published electronic and muonic x-ray isotope shifts to yield $\ensuremath{\delta}〈{r}^{2}〉$ values and some estimates of the specific mass shift constant.NUCLEAR STRUCTURE $^{156\ensuremath{-}164}\mathrm{Dy}$. Measured optical isotope shifts and hyperfine splittings. Deduced $\ensuremath{\delta}〈{r}^{2}〉$, $A(4{f}^{12}6s6p)$, $B(4{f}^{12}6s6p)$, and the hyperfine anomaly. Laser spectroscopy on atomic beams.

Hyperfine structure and isotope shift of the D 2 line of 118–145Cs and some of their isomers

High-resolution laser spectroscopy has been performed on 118–145Cs and 119m, 121m, 122m, 130m, 134m, 135m, 136m, 138m,Cs.The Cs nuclei have been produced either by spallation of La or by fission of U by the 600 MeV proton beam, from the SC at CERN. The hyperfine structures, spins, and isotope shifts have been measured. The charge radii changes deduced from the isotope shifts exhibit shell effects at N = 82, isomeric staggering for N = 64,66,67 and a strong odd-even staggering for all isotopes with N < 82.

Hyperfine structure and isotope shift of theD2line ofRb76−98and some of their isomers

Hyperfine structure, spin, and isotope shift measurements have been performed on $^{76\ensuremath{-}98}\mathrm{Rb}$ and $^{78,81,82,84,86,90}\mathrm{Rb}^{m}$. The Rb nuclei have been produced either by spallation of Nb or by fission of U by a 600 MeV proton beam. They have been separated in mass before being transformed into a thermal atomic beam which interacts at a right angle with the light from a c.w. tunable dye laser. The charge radii changes deduced from the isotope shifts exhibit shell effects at $N=50$ and deformations at $N=60$, which are discussed.NUCLEAR STRUCTURE $^{76\ensuremath{-}98}\mathrm{Rb}$, $^{78,81,82,84,86,90}\mathrm{Rb}^{m}$. Measured hyperfine constants $A(5s^{2}\mathrm{S}_{\frac{1}{2}})$, $A(5p^{2}\mathrm{P}_{\frac{3}{2}})$, $B(5p^{2}\mathrm{P}_{\frac{3}{2}})$; spins, isotope shifts. Deduced $\ensuremath{\mu}$, $\mathrm{Qs}$, $\ensuremath{\delta} 〈{r}^{2}〉$. High resolution laser spectroscopy on thermal atomic beams.

Laser techniques in nuclear physics

The hyperfine structure and isotope shift of atomic spectra have been in the past the main source of information on spins,moments and changes in charge radii of nuclear ground states. With the powerful tool of tunable dye lasers a variety of new spectroscopic methods have been developped in recent years leading to a general breakthrough in resolution and sensitivity of optical spectroscopy. Some of them have been especially designed to fit the demands of an on-line spectroscopy of radioactive nuclides which are produced in minute samples only. This paper will describe the principles, applications and results of these experiments.