I.S. Grant

New results on

The very neutron-deficient isotope was produced in the reaction at 195 MeV and was identified using the Daresbury recoil separator. A pure -ray spectrum belonging to the de-excitation of the excited states of was obtained in-beam. Twenty -ray lines were identified, ten of them for the first time. The intensity balance concerning some of these -rays together with the results obtained from the coincident measurements show the existence of a new set of levels which may be interpreted as being a side band confirming the coupling of and configurations.

Isotope shifts and hyperfine splitting in144-154Sm I

The isotope shifts and hyperfine splitting have been measured in 144-154Sm I using the crossed-beam laser fluorescence method. Transitions at 598.98 nm and 570.68 nm were investigated for all isotopes except 146Sm and 153Sm, in which measurements were only obtained at 570.68 nm. Laser-induced fluorescence has not previously been reported for 145Sm: the hyperfine structure for the ground state of this isotope leads to mu =1.123 mu N, Q(spectroscopic)=-0.60e2b2 and delta (r2) (144-145)=0.11 fm2. The magnetic dipole and electric quadrupole moments of the odd isotopes and the changes in mean square radii of the even ones are shown to be consistent with the information obtained from nuclear spectroscopy.

The Gamow-Teller transitions in the96Pd→96Rh decay

Using the40Ca(4.2 MeV/u) +60Ni reaction and on-line mass separation, the decay properties of4696Pd50 were reinvestigated. From a comparison of experimental and theoreticalβ+/(EC +β+) probability ratios, theQEC value was deduced to be 3,450 ± 150 keV. The strength was determined for four 0+→1+ Gamow-Teller beta transitions and found to be quenched as compared to predictions of the single-particle shell model. For96Pd and94Ru the sources of this quenching are discussed.

Quadrupole moments and mean square charge radii in the bismuth isotope chain

Abstract Isotope shifts and hyperfine structures of the 205,206,208,210,210m,212,213 Bi isotopes have been studied on the 306.7 nm line using gas cell laser spectroscopy. The neutron-rich isotopes are the first isotones of Pb to be measured immediately above the N = 126 shell closure. The ground state quadrupole moments of the even- N isotopes increase as neutrons are added or removed from the N = 126 shell, but no corresponding increase is observed in the charge radii.

Measurements of proton separation-energies close to the proton drip line in the antimony—cesium region

Abstract Mass-excesses and proton separation energies are determined for 114Cs, 110I and 106Sb - the lightest known isotopes of cesium, iodine and antimony. The localization of the proton drip line is discussed.

Coincidence laser spectroscopy: A new ultrasensitive technique for fast ionic or atomic beams

Abstract A new technique for laser spectroscopy of fast ionic or atomic beams is described. This involves measuring coincidences between resonantly scattered photons and ions (or atoms) in the fast beam. Measurements on strontium ions have shown that Doppler-free spectroscopy is possible with fewer than 100 ions s -1 .

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.

Position sensitive detection of photons in ultrasensitive fluorescent spectroscopy

Abstract The use of a position sensitive detector for ultrasensitive laser spectroscopy is described. The detector has been used in conjunction with coincidence laser spectroscopy of fast ionic/atomic beams to produce significant improvements in sensitivity.

A comparison of RIST and ISOLDE tantalum targets and geometries used on-line at ISOLDE

Abstract A comparison is made of the performance of RIST and ISOLDE tantalum targets used on-line at the CERN-ISOLDE isotope separator. The data is taken from a combination of recent measurements at the CERN-PSB and from the former ISOLDE facility at the CERN-SC. Developments in the target geometry have been necessary for the RIST project which aims to design a target capable of dissipating the power developed by an 800 MeV, 100 μA proton beam. These designs are being tested at the ISOLDE-PSB facility and the initial results are reported in comparison with data obtained from typical ISOLDE tantalum-foil targets. The study shows that improvements in the release properties of a number of elements can be made by a judicious choice of target matrix geometry. The target represents a complex system where, in general, modelling alone involves too many parameters to generate a reliable model of the target. From this study, it is clear that further practical work, following simple ideas such as those based on modifications of the target geometry, is necessary in order to obtain progress in the optimisation of the target design.

Fluorescent atom coincidence spectroscopy of extremely neutron-deficient barium isotopes

Abstract Fluorescent atom coincidence spectroscopy (FACS) has been used to measure the nuclear mean square radii and moments of the extremely neutron-deficient isotopes 120–124Ba. At N=65 an abrupt change in nuclear mean square charge radii is observed which can be understood in terms of the occupation of the spin-orbit partner g 7 2 5 2 [413] neutron and g 9 2 9 2 [404] proton orbitals and the consequent enhancement of the n-p interaction.