Collinear Fast-beam Laser Spectroscopy Research Articles

Hyperfine structure and isotope shift investigations in202–222Rn for the study of nuclear structure beyond Z=82

The hyperfine structure (hfs) and isotope shift (IS) in the isotopic chain of the radioactive element radon have been studied for the first time. The measurements were carried out by collinear fast-beam laser spectroscopy at the mass separator facility ISOLDE at CERN. The IS between 16 isotopes in the mass range 202≦A≦222 and the hfs of 7 odd-A isotopes were determined in the transitions 7s [3/2]2-7p [5/2]3 (745 nm) of Rn I. The nuclear spins and moments, as well as the observed inversion of the odd-even staggering for218–222Rn, can be associated with the effects of octupole instability around N=134.

Spins, moments and mean square charge radii of 104–127In determined by laser spectroscopy

Hyperfine structures and isotope shifts of indium isotopes in the mass range 104–127 have been measured in the atomic transitions 5 p 2 P 1 2 -6 s 2 S 1 2 (410 nm) and 5 p 2 P 3 2 -6 s 2 S 1 2 (451 nm) by collinear fast-beam laser spectroscopy. Nuclear magnetic dipole and electric quadrupole moments have been determined for 37 ground and isomeric states. The magnetic moments in the sequence of the 1 2 − isomers are found to cross the Schmidt limit. Magnetic dipole and electric quadrupole moments of the odd-odd isotopes are compared to values obtained by additivity rules. The 8 − isomers exhibit a strong change in the coupling of the h 11 2 neutrons to the collective motion. The mean square charge radii show a parabolic behavior with a maximum in the middle of the neutron shell at N = 66. This is interpreted by collective effects, which are considerably stronger than seen in the quadrupole moments or in the B(E2) values of neighbouring doubly-even nuclides.

Hyperfine structure of 4f126s and 4f125d Configurations in 167Er II Measured by Collinear Fast-Beam Laser and Radio-Frequency Laser Double-Resonance Spectroscopy

The collinear fast-beam-laser and rf-laser double-resonance technique has been used to make precise measurements of the magnetic dipole and electric quandrupole hyperfine constants of several states belonging to the 4f126s and 4f125d manifolds in 167Er II. The experimental data are analyzed within the Sandars-Beck effective-operator formalism by means of the parametric fitting approach, and a discussion of the results based on state-dependent ab initio multiconfiguration Dirac-Fock (MCDF) calculations of the magnetic dipole and electric quadrupole hyperfine constants is given. A 25% deviation between the experimental and ab initio MCDF values for the contact parameter ⟨r-3⟩6s10 is found, and possible causes of this discrepancy are discussed. In particular, the influence of the magnetic part of the Breit Hamiltonian on the reduced radial parameters of the Sandars-Beck theory has been investigated.

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 for181–206Hg is given, with a revised evaluation of the differences in nuclear mean square charge radii and of spectroscopic quadrupole moments.

Collinear laser spectroscopy on108g, 108m In using an ion source with bunched beam release

The hyperfine structure and isotope shift of108gIn and108mIn have been investigated by means of collinear fast-beam laser spectroscopy in the resonance line atλ=451 nm. The indium isotopes were prepared at the GSI on-line mass separator following a fusion evaporation reaction. For the first time, a FEBIAD ion source with bunched release of indium was used. Magnetic dipole moments, electric quadrupole moments and isotope shifts were determined. The present results lead us to assign the spinI=2 to the108In (T 1/2=40 min) state. Spins and moments are discussed in the framework of thejj-coupling model.

Nuclear moments and charge radii of105, 106In

With high resolution collinear fast beam laser spectroscopy in the 451 nm-line of Indium nuclear moments and the change in the mean square radii of the nuclear charge distribution of105,106 In have been determined.

Nuclear Magnetic Moment ofTl207

The magnetic moment 1.876(5)${\mathrm{\ensuremath{\mu}}}_{\mathit{N}}$ of 4.77-min $^{207}\mathrm{Tl}$, the only heavy nucleus with a doubly magic core plus a single ${s}_{\frac{1}{2}}$ particle or hole, was measured from the hfs by collinear fast-beam laser spectroscopy at ISOLDE (isotope separator at the CERN synchrotron). The result is of theoretical importance as a test case for core polarization since the nuclear structure is relatively simple and the orbital part of the magnetic moment, including strong pion-exchange contribution, is expected to be zero.

Nuclear magnetic moment of 207Tl.

The magnetic moment 1.876(5)${\mathrm{\ensuremath{\mu}}}_{\mathit{N}}$ of 4.77-min $^{207}\mathrm{Tl}$, the only heavy nucleus with a doubly magic core plus a single ${s}_{\frac{1}{2}}$ particle or hole, was measured from the hfs by collinear fast-beam laser spectroscopy at ISOLDE (isotope separator at the CERN synchrotron). The result is of theoretical importance as a test case for core polarization since the nuclear structure is relatively simple and the orbital part of the magnetic moment, including strong pion-exchange contribution, is expected to be zero.

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) of107–111In. 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.

Nuclear spins, moments, and changes of the mean square charge radii of140?153Eu

The hyperfine structures and isotope shifts of 14 isotopes of Eu (Z=63) in the mass range 140≦A≦153, partly with isomeric states, have been measured in the atomic transitions at 4,594 A and 4,627 A, using the technique of collinear fast-beam laser spectroscopy at the ISOLDE facility at CERN. The nuclear spins, the magnetic dipole and electric quadrupole moments, and the changes in the mean square charge radii have been evaluated. These nuclear parameters clearly reflect the effects of theN=82 neutron-shell closure in the single-proton hole states with respect to the semi-magic gadolinium (Z=64), and theN=88−90 shape transition.

Hyperfine interactions in the alkaline-earth Sr ions by collinear fast beam laser spectroscopy

The magnetic dipole hyperfine structure constants of the87SrII 5s2S1/2 ground state and the 5p2P1/2 excited state, and the isotope shifts of the ionic 5s2S1/2 → 5p2P1/2 resonance transition for all stable Sr isotopes, measured by collinear fast beam laser spectroscopy, are reported.

Determination of nuclear spins and moments in a series of radium isotopes

The first investigation of hyperfine structure in radium isotopes has enabled the determination of nuclear spins, magnetic dipole and electric quadrupole moments of the isotopes with mass numbers A = 211, 213, 221, 223, 225, 227 and 229. Isotope shifts in the mass range A = 208−232 have also been measured. These studies were carried out using the technique of on-line collinear fast beam laser spectroscopy.

Nuclear moments and charge radii of rare-earth isotopes studied by collinear fast-beam laser spectroscopy

The collinear fast-beam laser technique is being used to measure systematically hyperfine structures and isotope shifts of unstable nuclides in the rare-earth region. This brief report gives a general survey of the results obtained for the even-Z elements64Gd,66Dy,68Er and70Yb, with emphasis on the nuclear spins and moments. They allow a rather complete mapping of the single-particle structure and the development of nuclear deformation in the N > 82 region. The spins, magnetic moments and spectroscopic quadrupole moments of159–169Yb are presented in detail.

Spins, moments and charge radii of barium isotopes in the range 122–146Ba determined by collinear fast-beam laser spectroscopy

Hyperfine structures and isotope shifts of barium isotopes in the mass range 122–146 have been measured in the atomic transition 6 s 2 1 S 0→6 s6 p 1 P 1 (5536 A ̊ ) , utilizing collinear fast-beam laser spectroscopy at the ISOLDE facility at CERN. Nuclear spins, magnetic dipole and electric quadrupole moments, and the changes of mean square charge radii have been deduced. They are discussed within the framework of current nuclear models, revealing single-particle structure and nuclear-shape variations on both sides of the N = 82 neutron-shell closure.

Collinear fast-beam laser spectroscopy experiment: Measurement of hyperfine structure and isotope shifts in Xe II

As an initial test of a new laser spectroscopy system placed on line to the UNISOR isotope separator, the hyperfine structure of 131Xe II and 129Xe II in their 5 d 4 D 7 2 and 6 p 4 P 5 2 levels has been investigated along with isotope shifts for 128–131, 134, 136Xe relative to 132Xe. The method utilizes the resonant absorption of laser light collinear to the beam of ∼50 keV Xe ions from the isotope separator. The spectra were produced by scanning a ring dye laser over a small frequency range and continuously monitoring the absorption through subsequent fluorescence of the 4 P 5 2 level. Laser and other electronic drifts during the course of the measurements were small and were monitored through simultaneous absorption of a portion of the laser light in an I 2 cell. The measured hyperfine constants and isotope shifts are compared with earlier results and δ〈 r 2〉 are deduced from the isotope shifts.

J-dependent isotope shifts in the 5d2DJdoublet of barium II

A J dependence is revealed in the isotope shifts of the 5d2D3/2, 5/2 to 6p2P3/2 transitions in Ba ions, using collinear fast-beam laser spectroscopy. The experimental ratio of the field shift for the 5d2D3/2 to 6p2P3/2 transition to that for the 5d2D5/2 to 6p2P3/2 transition is 1.0465+or-0.0010. This result is compared with relativistic Hartree-Fock calculations.

Parallel-antiparallel measurements in collinear fast beam laser spectroscopy

In collinear fast beam-laser spectroscopy, additional information can be obtained when, between two consecutive measurements, the direction of the laserbeam is inverted with regard to the atom beam. From these measurements accurate isotope shifts (0.1 MHz) and mass values (100 keV) can be extracted without knowledge of the effective acceleration voltage.

Hyperfine structures and isotope shifts of the 5d 4 D 7/2?6p 4 P 5/2 0 transition in Xenon ions

Collinear fast beam-laser spectroscopy has been performed on metastable 5d4D7/2 Xenon ions. Hyperfine structure constants for the 6p4P5/20 level have been derived for129Xe:A=−1,634.9±0.9 MHz and131Xe:A=485.3±0.3 MHz andB=−116.5±2.0MHz. Changes in mean squared nuclear charge radii are derived from the measured isotope shifts.