Nuclear spins of neutron-deficient thulium isotopes

Cyclotron-produced thulium isotopes have been investigated using the atomic-beam magnetic resonance method. The spin measurements have given the following results: ¹⁵⁹Tm (9 min) , ¹⁶⁰Tm (9 min) I = 1, ¹⁶¹Tm (37 min) , ¹⁶²Tm (21.5 min) I = 1, ¹⁶⁴Tm (2 min) I = 1, ^164m Tm (5 min) I = 6 and ¹⁶⁸Tm (87 d) I = 3. An interpretation based on the Nilsson diagram for odd protons clearly indicates a systematic variation in the nuclear deformation.     

Nuclear moments of the neutron-deficient thallium isotopes

The nuclear moments of the neutron-deficient^187,188Tl isotopes were determined by measuring the hyperfine structure splittings of the λ=535 nm line in neutral thallium. An optical efficiency of 2×10⁻⁴ photons per radioactive ion was achieved using collinear fast beam laser spectroscopy with a large solid angle fiber optical array detector. Most of the moments can be interpreted fairly well in the single particle model.     

Nuclear shape transition in neutron-deficient gold isotopes

On-line resonance ionization mass spectrometry has been applied to determine the isotope shift and hyperfine structure of^185–189Au and tne I=11/2 isomer of¹⁸⁹Au in the 6s²S_1/2 6p²P_1/2=268 nm) transition. The Au atoms were obtained as daughters of mass-separated Hg isotopes produced at the ISOLDE facility at CERN, ionized by a three-step resonant photoionization process, detected and mass-selected by time of flight. A drastic change of the nuclear charge radius was observed between¹⁸⁷Au and¹⁸⁶Au, which is interpreted as an onset of strong deformation of ₂ 0.25 in¹⁸⁶Au and¹⁸⁵Au.This work has been supported by the Bundesministerium für Forschung und Technologie. One of us, J. Wood was supported in part by the U.S. Department of Energy, Contract DE-AS05-80 ER 10599.     

Nuclear spin measurements of neutron-deficient isotopes of the refractory elements

Nuclear ground and isomeric state spins of several isotopes of the refractory elements (Y, Nb, Mo, Tc, Rh, Ta, Re, Os, Ir, Pt) measured by the atomic beam magnetic resonance method, are reported. The atomic ground-state g-factor for the Os atom has also been measured.     

Nuclear spins and magnetic moments of some neutron-deficient rubidium isotopes

The nuclear spins and magnetic moments of some neutron-deficient rubidium isotopes have been measured by atomic-beam magnetic resonance techniques at the ISOLDE facility, CERN. The following results have been obtained: ⁷⁷Rb, $\text{I =}\text{3}\text{2}\text{, μ}{}_{\mathrm{I}}\text{= 0.652(7)}\text{n.m.}$; ⁷⁸Rb, I = 0; ^78mRb,I = 4, μ_I = 2.56(3)(rmn.m.); $\text{(su79)}\text{Rb}\text{, I =}\text{5}\text{2}\text{, ifμ}{}_{\mathrm{I}}\text{= 3.364(4)}\text{n.m.}\text{,}\text{and}{}^{\mathrm{<mtext>84</mtext><mtext>m</mtext>}}\text{Rb}\text{, I = 6}$.The data on the The data on the light rubidium isotopes gives evidence for deformed nuclear shapes     

Beta-decay of even-A neutron-deficient Pr isotopes

Even-A praseodymium activities have been produced and identified in the⁴⁰Ca +^92–96Mo reactions at 5.8 MeV/u:¹²⁶Pr[T_1/2=(3.0 ±0.4)s]¹²⁸Pr[T_1/2=(3.1 ±0.3)s],¹³⁰Pr[T_1/2 =(40.0 ±0.4)s]¹³²Pr[T_1/2=1.6 min]. Several new low-energy levels have been populated in even-even cerium nuclei.     

Ground-state properties of neutron-deficient platinum isotopes

The hyperfine structure splitting and the isotope shift in the =266 nm transition of Pt isotopes within the mass range 183 A 198 have been determined by Resonance Ionization Mass Spectroscopy (RIMS) in combination with Pulsed-Laser Induced Desorption (PLID). The Pt isotopes were obtained at the on-line isotope separator ISOLDE-3/CERN as daugthers of the primarily produced Hg isotopes. Magnetic moments, quadrupole moments, and changes in the mean-square charge radii are deduced and compared with results of a particle-triaxial rotor model and mean field calculations. Good agreement with experimental data (including nuclear level schemes and transition probabilities) can only be obtained if triaxial shape is admitted. The calculations yield a smooth transition in the shape of odd-A Pt nuclei from a slightly deformed, nearly oblate¹⁹⁵Pt via triaxial^197-187Pt to a strongly deformed nearly prolate¹⁷⁷Pt.Dedicated to P. Armbruster on the occasion of his 60th birthday     

New neutron-deficient isotopes of lanthanum and cerium

The short-lived neutron-deficient isotopes of lanthanum and cerium were produced in the ³²S+^{96, 98}Ru reactions and separated according to their masses. Seven isotopes ^123–125La and ^124–127Ce have been first observed and their half-lives and low-energy γ-ray data are reported. In addition, low-energy γ-ray data are given for the ^122–125Ba and ¹²⁷La decays. The β-decay probabilities for Ce, La and Ba isotopes are discussed in terms of the average β-strength function.     

Alpha decay of neutron-deficient isotopes of tungsten

Three neutron-deficient isotopes of tungsten have been produced by the reactions of ²⁴Mg on targets of ¹⁴⁷Sm and ¹⁴⁴Sm. They are ¹⁶⁴W, E_α = 5.153 MeV, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 6.3 s}$; ¹⁶³W, E_α = 5.385 MeV, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 2.5}\text{s}$; and ¹⁶²W, E_α = 5.53 MeV, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{< 0.25}\text{s}$.     

Alpha decay studies of neutron-deficient radium isotopes

Neutron-deficient isotopes of radium have been produced in the reactions ³⁵Cl + ¹⁷⁵Lu, ⁴⁰Ar + ^170,171Yb, and ³⁶Ar + ^170,171Yb and separated in-flight with a gas-filled recoil separator. The activities have been identified on the basis of correlated alpha decay chains. The alpha particle energy E_α and the half-life T_1/2 of an isomeric state of the new isotope, ^203mRa, have been determined to be (7615±20) keV and (33 _?10 ⁺²² ), respectively. An assignment of another decay with E_α = (7577±20) keV and T_1/2 = (1.1 _?0.5 ^+5.0 ) ms to ^203g Ra is made on the basis of one observed three-decay chain. Tentative evidence for the production of the new isotope ²⁰²Ra is also given. The values E_α = (7860±60) keV and T_1/2 = (0.7 _?0.3 ^+3.3 ) ms were measured. Improved decay data have been obtained for ²⁰⁴Ra. The results are E_α = (7484±10) keV and T_1/2 = (59 _?9 ⁺¹² ). Earlier findings concerning the decay of two states in ²⁰⁵Ra and an isomer in ²⁰⁷Ra have been confirmed. Approximate values for cross sections have been determined for ²⁰²Ra, produced using the ³⁶Ar + ¹⁷⁰Yb reaction and for ²⁰³Ra, ²⁰⁴Ra, and ²⁰⁵Ra using the ³⁵Cl + ¹⁷⁵Lu reaction. The results are 2 nb (²⁰²Ra), 4 nb (²⁰³Ra), 40 nb (²⁰⁴Ra), and 800 nb (²⁰⁵Ra).     

Investigation of neutron-deficient isotopes in the barium-region

Bombarding targets of 106Cd,¹⁰⁸Cd and¹¹⁰Cd with¹⁶O ions of 52.5–66.0 MeV neutron deficient barium, cesium and xenon isotopes were produced and have been studied using excitation functions and neutron-gamma, proton-gamma, alpha-gamma and gammagamma coincidence measurements. Partial level schemes for¹²³Ba and¹²¹Ba were proposed. A number of gamma transitions was assigned to the different product nuclei. The measured particle emission probabilities from the compound nuclei are compared with different evaporation models. The models mostly underestimate neutron emission and often overestimate the emission of alpha particles.     

Studies of neutron-deficient mendelevium isotopes at SHIP

The radioactive decay of the isotopes ²⁴⁷Md , ²⁴⁶Md and their daughter products was investigated by means of $ \alpha$ - $ \alpha$ and $ \alpha$ - $ \gamma$ coincidence spectroscopy. The isotopes were produced using the fusion reaction ⁴⁰Ar$ + $²⁰⁹Bi. Decay schemes are suggested for ²⁴⁷Md and ²⁴³Es . A new isomeric state in ²⁴⁶Md with a half-life of ( 4.4±0.8 s was observed. Previous data of electron-capture delayed fission of ²⁴⁶Md and ²⁴²Es were confirmed. The probability for this decay branch in ²⁴⁶Md was measured to be P _ECDF > 0.10 . The probability for electron-capture delayed fission in the case of ²⁴²Es was determined to be P _ECDF = 0.013^+0.012 _-0.007 .     

Alpha decay studies of neutron-deficient radium isotopes

Neutron-deficient isotopes of radium have been produced in the reactions³⁵Cl+¹⁷⁵Lu,⁴⁰Ar+^170,171Yb, and³⁶Ar+^170,171Yb and separated in-flight with a gas-filled recoil separator. The activities have been identified on the basis of correlated alpha decay chains. The alpha particle energy E_α and the half-life T_1/2 of an isomeric state of the new isotope,^203m Ra, have been determined to be (7615±20) keV and (33 _?10 ⁺²² ) ms, respectively. An assignment of another decay with E_α = (7577±20) keV and T_1/2=(1.1 _?0.5 ^+5.0 ) ms to^203g Ra is made on the basis of one observed three-decay chain. Tentative evidence for the production of the new isotope²⁰²Ra is also given. The values E_α = (7860±60) keV and T_1/2=(0.7 _?0.3 ^+3.3 ) ms were measured. Improved decay data have been obtained for²⁰⁴Ra. The results are E_α = (7484±10) keV and T_1/2=(59 _?9 ⁺¹² ) ms. Earlier findings concerning the decay of two states in²⁰⁵Ra and an isomer in²⁰⁷Ra have been confirmed. Approximate values for cross sections have been determined for²⁰²Ra, produced using the³⁶Ar+¹⁷⁰Yb reaction and for²⁰³Ra,²⁰⁴Ra, and²⁰⁵Ra using the³⁵Cl+¹⁷⁵Lu reaction. The results are 2 nb (²⁰²Ra), 4 nb (²⁰³Ra), 40 nb (²⁰⁴Ra), and 800 nb (²⁰⁵Ra).     

Investigation of neutron-deficient isotopes in the barium-region

Bombarding targets of 106Cd,¹⁰⁸Cd and¹¹⁰Cd with¹⁶O ions of 52.5–66.0 MeV neutron deficient barium, cesium and xenon isotopes were produced and have been studied using excitation functions and neutron-gamma, proton-gamma, alpha-gamma and gammagamma coincidence measurements. Partial level schemes for¹²³Ba and¹²¹Ba were proposed. A number of gamma transitions was assigned to the different product nuclei. The measured particle emission probabilities from the compound nuclei are compared with different evaporation models. The models mostly underestimate neutron emission and often overestimate the emission of alpha particles.     

New neutron-deficient isotopes of barium and rare-earth elements

This paper deals with an investigation of the short-lived neutron-deficient isotopes of barium and rare-earth elements. By using the BEMS-2 isotope separator with a heavy-ion beam, we succeeded in producing 19 new isotopes with mass numbers ranging from 117 to 138. Five of these (¹¹⁷Ba, ^{129, 131}Nd and^{133, 135}Sm) turned out to be delayed proton emitters. Theβ-decay probabilities for the new isotopes have been analyzed in terms of the β-strength function. An analysis of the proton spectrum shape has been performed using the statistical model for delayed proton     

Alpha decay of neutron-deficient rhenium and osmium isotopes

Neutron-deficient osmium and rhenium isotopes were produced by bombarding an enriched¹⁴⁴Sm target with beams of²⁷Al and²⁸Si. Previously reported decay data concerning^168,169,170Os were confirmed. Three newα groups, observed in the¹⁴⁴Sm+²⁷Al reaction, were assigned to the decay of^166,167,168Re based on excitation functions,α-energy systematics and theoretical half-life predictions. Their decay properties are: $$\begin{gathered} {}^{166}\operatorname{Re} , E_\alpha = 5,372 (10) keV, T_{1/2} = 2.8 (3) s; \hfill \\ {}^{167}\operatorname{Re} , E_\alpha = 5,136 (8) keV, T_{1/2} = 6.1 (2) s and \hfill \\ {}^{168}\operatorname{Re} , E_\alpha = 4,894 (10) keV, T_{1/2} = 6.9 (8) s. \hfill \\ \end{gathered}$$ It is proposed that twoα groups, observed in the¹⁴⁴Sm+²⁸Si reaction, originate from isomeric states in^168,169Re. Our measured data for the isomeric states are: $$\begin{gathered} {}^{168m}\operatorname{Re} , E_\alpha = 5,250 (10) keV, T_{1/2} = 6.6 (15) s and \hfill \\ {}^{169m}\operatorname{Re} , E_\alpha = 5,050 (10) keV, T_{1/2} = 12.9 (11) s. \hfill \\ \end{gathered} $$      

Alpha-decay widths of neutron-deficient francium and astatine isotopes

The use of mass-separated samples of neutron-deficient francium isotopes, produced at the ISOLDE on-line mass-separator facility at the CERN 600 MeV synchro-cyclotron, has permitted precise determinations through genetic relationships of /(EC+β⁺) branching ratios for a range of light francium and astatine isotopes. The experiments verify previous mass assignments and provide improved values for the half-lives. The systematics of -widths and of β-strength functions is surveyed.     

Beta-decays of172–175Ir neutron-deficient isotopes

Theβ-decays of^172–175Ir have been studied using a Hejet system through³²S induced reactions,β half-lives have been measured and compared with those given fromα decays. The level schemes of osmium nuclei are deduced and for¹⁷²Os and¹⁷⁴Os, the 2₂ ⁺ level is possibly located. The observedβ-decay half-lives clearly indicate an isomerism phenomenon occuring in light Ir isotopes.     

Nuclear charge radii of neutron-deficient lead isotopes beyond N = 104 midshell investigated by in-source laser spectroscopy

The shape of exotic even-mass (182-190)Pb isotopes was probed by measurement of optical isotope shifts providing mean square charge radii (delta(r(2))). The experiment was carried out at the isolde (cern) on-line mass separator, using in-source laser spectroscopy. Small deviations from the spherical droplet model are observed, but when compared to model calculations, those are explained by high sensitivity of delta(r(2)) to beyond mean-field correlations and small admixtures of intruder configurations in the ground state. The data support the predominantly spherical shape of the ground state of the proton-magic Z=82 lead isotopes near neutron midshell (N=104).