J. A. R. Griffith

Nuclear charge radii of neutron deficient titanium isotopes 44Ti and 45Ti

Optical isotope shifts of the unstable 44,45Ti isotopes, as well as those of stable 46−50Ti, have been investigated by collinear laser spectroscopy on fast ion beams using an ion guide isotope separator with a cooler-buncher. Changes in mean square charge radii across the neutron 1f7/2 shell are deduced. The evolution of the even-N Ti nuclear radii shows a generally increasing tendency with decreasing neutron number. This behaviour is significantly different to that of the neighbouring Ca isotopes which exhibit a symmetric parabolic behaviour across the shell. The trend of the Ti nuclear radii is consistent with the predictions of the relativistic mean-field theory. The charge radius of 44Ti is also compared to predictions of a 40Ca + α cluster model.

Collinear laser spectroscopy of radioisotopes of zirconium

Isotope shifts and hyperfine structures have been measured for radioisotopes of ionic zirconium using on-line laser spectroscopy at the IGISOL facility in Jyvaskyla, where the installation of an ion beam cooler/buncher has significantly improved the experimental sensitivity. Measurements have been made on all the neutron-deficient isotopes from 87Zr to 90Zr, including the isomers 87m,89mZr, and the neutron-rich isotopes from 96Zr to 102Zr. The change in mean square charge radii between the isotopes and the nuclear moments of the odd isotopes have been extracted. The data show a sudden increase in the mean square charge radius at mass A = 100, consistent with an onset of nuclear deformation which has been observed in the gamma ray spectroscopy of isotope chains in this region of the nuclear chart.

Nuclear moments and charge radii of the 171Hf ground state and isomer

The magnetic moment, quadrupole moment and mean-square charge radial changes, relative to 172Hf, have been measured for the 171Hf ground state and the ½-[521] isomeric state, using on-line laser spectroscopy. The magnetic moments of the isomer and ground states are found to be + 0.526(16)µn and -0.674(12)µn, respectively. The spectroscopic quadrupole moment of the ground state is found to be +3.463(27) b. No change in mean-square charge radius is observed between the ground state and isomeric state. The observation of an inversion in the odd-even staggering at 171Hf is consistent with the suggested deformation trends.

First collinear laser spectroscopy measurements of radioisotopes from an IGISOL ion source

Abstract The standard Doppler-free technique of collinear laser spectroscopy has been successfully applied to radioisotopes from the ion-guide isotope separator (IGISOL) at the University of Jyvaskyla. The laser resonance fluorescence signals for the 140,142,144 Ba radioisotopes show that the ion beam energy spread is less than 6 eV, allowing the laser technique to have both high resolution and a sensitivity comparable with the best obtained at conventional facilities.

Hyperfine structure and isotope shifts in natural vanadium

High-resolution crossed beam laser spectroscopy has been performed on an atomic beam of natural vanadium. The hyperfine structure was measured in highly resolved spectra for 25 transitions from the first metastable states, 3d 4 .a 5 D/4s a 6 DJ , to two high-lying multiplets, 3d 3 4s.a 5 F/4p z 6 D o and 3d 3 4s.a 5 F/4p z 6 F o . This yielded the hyperfine A.J/ and B.J/ coefficients of 16 51 V fine structure states, including the six previously unstudied levels in the z 6 F o multiplet. Excellent agreement was found between these values and those obtained from atomic beam magnetic resonance experiments for the metastable states. In addition, the hyperfine structure of 50V was measured in eight transitions to the upper state multiplet z 6DJ . This resulted in the evaluation of hyperfine coefficients for all 10 levels of the upper and lower states, previously unknown, as well as the first optical isotope shift measurements for vanadium.

A thirty second isomer in Hf-171

An isomer has been detected in Hf-171 with a half-life of T-1/2 = 29.5(9) s. The state was populated in the Yb-170(alpha,3n)Hf-171m reaction at a beam energy of E-alpha = 50 MeV in an on-line ion guide isotope separator. The isomeric Hf-17lm(+) beam was extracted from the ion guide, mass-analysed and implanted in the surface of a microchannel-plate. The half-life of the collected activity was measured from the decay of the microchannel-plate count rate. We associate the isomer with the first excited slate in Hf-171 with spin 1/2(-) at an excitation energy of 22(2) keV.

A detailed study of the effects of weak magnetic fields on the forward scattering of resonant laser light by sodium vapour

The effects of magnetic optical activity in the sodium D1 line are investigated in detail both theoretically and experimentally. Particular consideration is given to the ultra-narrow Hanle-type features that are produced by the crossing of ground state Zeeman sub-levels and which although strongly exhibited by the Fg=2 to Fe=1, 2 doublet, are apparently absent from the Fg=1 to Fe=1,2 doublet. We demonstrate, quantitatively for the first time, that these features are principally a manifestation of Delta M=2 (quadrupole) coherences and are therefore not evidence for the existence of Delta M=4 (hexadecapole) coherences as originally proposed by Gawlik and co-workers (1987). Indeed the latter is shown to have little influence on these features even at light field intensities for which significant power broadening is observed. We also show explicitly that the width of these narrow crossing features is, for the typical vapour pressures used to give an optically thin sample, a function of the average time of transit through the light field. Using a simple phenomenological model we predict numerically both the absolute width of these coherence features and the rate at which they power broaden. Finally a brief consideration of the same coherence effects within the D2 line is presented.

J dependence of the field and mass isotope shifts in the ground term of Sm I

Laser heterodyne spectroscopic measurements of the optical isotope shifts between the naturally occurring even-even isotopes of samarium have been made in eleven lines of the Sm I spectrum. These have been used to study the J-dependent differences between the isotope shifts of the levels of the ground term which were recently discovered by Bauche and co-workers (1977). The present work confirms the experimental results of these authors and, by including more than one isotope pair, allows the field and mass shift contributions to the total J dependence to be separated from each other. It is found that the proportion of the observed J dependence due to the field shift is at least four times that due to the mass shift: these results are not quite in accord with the theoretical results of Bauche et al.

High resolution laser spectroscopy of naturally occurring ruthenium isotopes

High resolution crossed atomic beam laser spectroscopy has been used to measure isotope shifts and hyperfine structures in 12 transitions in naturally occurring ruthenium isotopes. Improved values for the changes in mean square charge radii have been deduced from a combined analysis of optical isotope shift and muonic x-ray data.

Progress of laser spectroscopy at the IGISOL

The laser IGISOL facility at JYFL has successfully provided on line laser spectroscopy access to short lived isomers and refractory metal isotopes. A new ion beam cooler has been commissioned at the facility and the scope for future work has been greatly increased. The cooler can provide a low energy spread (∼1 eV), point like source of ions independent of their initial production conditions (a critical concern for spectroscopy at IGISOL facilities). New results for neutron deficient hafnium isotopes are reported. The fully operational cooler will enable future investigations to be directed at high K isomers, isotopes around Zr and at the light proton “halo” candidates.