Decay of the new isotope127Pr

A new isotope,¹²⁷Pr, has been identified and its decay has been studied using on-line isotope separation of⁹⁴Mo (³⁶Ar,p2n) reaction products. The half-life of the isotope was determined to be 7.7(6) s, and a /X-ray spectrum has been obtained. A partial level scheme is proposed for¹²⁷Ce on the basis of-singles,-gated and-coincidence data.The authors would like to thank the TIARA cyclotron crew for their cooperation in generating an intense³⁶Ar beam as well as in operating the cyclotron. This work was partly supported by the JAERI-University Collaborative Research Project.     

Identification of a new isotope,168Dy

A previously unreported nuclide,¹⁶⁸Dy, has been identified and found to have a half-life of 8.5+-0.5 min. The activity was produced in the spontaneous fission of²⁵²Cf and transported via a He jet system to a rapid radiochemical separative facility where the Dy fraction was removed from the mixed fission products. The assignment of this activity to¹⁶⁸Dy decay was based on the presence of five γ rays in the chemically separated Dy fraction which were associated with the decay of an 8.5-min activity and on the observation of the grow-in and subsequent decay of the daughter, 2.98-min¹⁶⁸Ho, with approximately an 8-min half-life. The γ-ray emission probabilities have been determined.     

Excited states of 154Nd studied through the decay of 154Pr

The neutron-rich isotope ¹⁵⁴Pr, the heaviest isotope of praseodymium, has been investigated by γ-ray multispectrum scaling and γ-γ-(t), X-γ-(t) coincidence experiments. The isotope ¹⁵⁴Pr was separated from ²³⁵U fission products with the on-line isotope separator KUR-ISOL. The decay scheme of ¹⁵⁴Pr has been constructed consisting of 9 excited states and 12 transitions in ¹⁵⁴Nd, including 7 excited states newly found in the present experiment.     

Excited states of154Nd studied through the decay of154Pr

Excited states in the neutron-rich doubly-odd nucleus⁷⁸As have been identified for the first time by proton-γ and γ-γ coincidence measurements via the⁷⁶Ge(α, pn) reaction at 32, 36, and 40 MeV beam energy. Four levels have been found to decay with lifetimes in the nanosecond region. The 5⁽⁺⁾ to (10⁺) states are ascribed to the (πg _9/2?νg _9/2) intruder two-quasiparticle configuration with some collective components in the 9⁽⁺⁾ and (10⁺) states.     

Identification of the new isotope 241Bk

A new neutron-deficient berkelium isotope ²⁴¹Bk produced in the ²³⁹Pu(⁶Li, 4n) reaction has been identified using a gas-jet coupled on-line isotope separator. Cm K and L X-rays associated with the EC decay of ²⁴¹Bk were observed in the mass-241 fraction, and three γ transitions were attributed to the EC decay of ²⁴¹Bk through X-γ coincidences. The half-life of ²⁴¹Bk was determined to be 4.6±0.4 min which is 1/2-1/4 of that of theoretical predictions. The half-life value and the observed γ transitions can be consistently explained as a consequence of the allowed EC transition of π7/2⁺[633] → ν7/2⁺[624]. Received: 14 October 2002 / Accepted: 6 November 2002 / Published online: 17 January 2003 RID="a" ID="a"e-mail: asai@tandem.tokai.jaeri.go.jp Communicated by J. ?yst?     

Identification of a new isotope of121La by means of element-selective mass separation

A new isotope of¹²¹La was produced in the reaction³²S +⁹²Mo and mass-separated as¹²¹La¹⁶O⁺, being well separated from¹²¹Cs and¹²¹Ba. From γ-ray measurement, the half-life of this isotope was determined to be 5.3±0.2 s. Its partial decay scheme is proposed.     

Decay of the heaviest isotope of neodymium:154Nd

Excited states in the two N=76 nuclei ¹³⁸ Sm and ¹³⁹ Eu have been identified via ³² S induced reactions on different targets using γ-ray spectroscopy methods. Lifetimes have been measured with the Doppler shift recoil distance technique, showing the coexistence of a large nuclear deformation (β=0.24) with excitations of single particle character. The E2 transition strengths in the odd-even nucleus ¹³⁹Eu and in its core¹³⁸ Sm are discussed.     

212Th,a new isotope

The new isotope²¹²Th has been found to decay withE _α = (7.802 ±0.010) MeV andt _1/2 =(30 _?10 ⁺²⁰ ms. The decay energies of the previously observed isotopes²¹³Th and²¹⁴Th could be confirmed. The measured half-lives are in agreement with calculated values.     

164Ta,identification of a new isotope

The new isotope¹⁶⁴Ta (T _1/2=13.6(2)s) was produced in the¹²⁷I(⁴⁰Ca, 3n) reaction and transported to a measuring station by helium jet. Decay properties were observed withα, γ, andγ-γ spectroscopy. TheZ assignment of the new isotope was based ongg-X-ray coincidence measurements. The mass assignment was deduced from measured excitation functions. The twoγ rays assigned to the new activity most likely originate from the 4⁺→2⁺→0⁺ decay sequence in¹⁶⁴Hf. A smallα branch, ≦0.016(5)%, with anα decay energy ofE _α=4,625(15) keV was found and assigned to the decay of¹⁶⁴Ta. The deduced upper limit of theα width for this branch,W _α≦0.6(2), is in accordance with those known for neighbouring nuclei.     

Identification and decay of102In,new neutron deficient isotope close to100Sn

¹⁰²In, [T_1/2=(24±4)s], has been identified for the first time using an on-line mass isotopic separator operating on nuclear reactions induced by heavy ions. Gamma-rays observed both in¹⁰²In→¹⁰²Cd decay and in-beam measurements allow to build a partial level scheme for¹⁰²Cd. Systematics of the two first excited states of even cadmium isotopes shows the special behaviour of the lightest one.     

Identification of the neutron-rich isotope174Er

The heaviest known erbium isotope, 3.3(2) min.¹⁷⁴Er, has been identified using on- line isotope separation and by ß and γ- ray spectroscopy. Twelve γ rays were placed in a preliminary decay scheme. The mass of the new isotope was established by the separator and the Z was deduced from Tm K x ray coincident ß and γ rays. In addition, the heaviest known isotope of holmium¹⁷¹Ho was observed with a half-life of 49(5) s.     

The new isotope219U

In continuation of our experimental program on investigation of evaporation residues (ER's) in the region close to N=126 [1, 2], the new neutron-deficient isotope²¹⁹U has been produced in the irradiations of an¹⁹⁷Au target with a beam of²⁷A1 ions. The identification of²¹⁹U was made establishing genetic position and time correlations between the implanted ER's with their subsequentα-decays. Theα-decay energy and half-life were measured to be (9680±40) keV and (42 _?13 ⁺³⁴ )μs, respectively. To separate the evaporation residues in-flight the kinematic separator VASSILISSA [3] was used.     

The new isotope 217U

The new neutron deficient isotope ²¹⁷U was produced in the bombardment of the ¹⁸²W target with ⁴⁰Ar ions and identified using a recoil-- correlation method. The -decay energy and the half-life of ²¹⁷U were determined to be 8005 ± 20 keV and 15.6 ^+21.3 _-5.7 ms, respectively. Received: 18 May 2000 / Accepted: 21 June 2000     

The new isotope218U

The new neutron-deficient isotope²¹⁸U was produced in the bombardment of¹⁹⁷Au target with²⁷Al ions and identified using the- correlation method. The -decay energy and the half-life of²¹⁸U were determined to be 8625±25 keV and 1.5 _–0.7 ^+7.3 ms, respectively. Evaporation residues recoiling from the target were separated in-flight from the projectiles and from the products of other nuclear reactions by the electrostatic separator VASSILISSA [1].     

The new neutron-rich isotope183Lu

The new neutron-rich isotope¹⁸³Lu was produced in multinucleon transfer reactions by irradiating^natW/Ta targets with 11.7 MeV/u¹³⁶Xe ions, and identified by mass separation and decay spectroscopy. The measured half-life of¹⁸³Lu is 58±4 s. The properties of the excited states of¹⁸³Hf are discussed.     

A new alpha-particle-emitting isotope 259Db

An isotope of the element 105 with mass number 259 has been produced via the reaction ²⁴¹Am(²²Ne, 4n)²⁵⁹Db at E _lab = 118 MeV. The reaction products were transported and collected using the helium-jet technique and the rotating wheel apparatus. The α-decays of the products and their daughter nuclides were detected by a set of Si(Au) detectors arranged ingeniously. The Z and A of the nuclide have been unambiguously identified by the genetic relationship between the new activity and the known nuclide ²⁵⁵Lr established by α-recoiled milking measurement. The new nuclide ²⁵⁹Db has a half-life of 0.51±0.16 s and decays by alpha-particle emission of E _α = 9.47 MeV. Furthermore, the nuclide ²⁵⁸Db and its daughter ²⁵⁴Lr have also been clearly observed using the same projectile-target combination. Their half-lives and α-particle energies determined in this work are in agreement with previous known data, thus also proving the reliability of our assignment of ²⁵⁹Db. Received: 7 December 2000 / Accepted: 6 February 2001     

Decay of the new isotope167W

Theα- and β-decay of the new isotope¹⁶⁷W were observed in the reaction of 191 MeV³⁶Ar with¹³⁶Ba using a helium-jet and a fast tape-transport system. The identification is based on coincidences with tantalum X-rays and excitation function measurements. The measured half-life is 19.9(5) s. A decay scheme comprising 12 levels was constructed from γγ-coincidences. The β-decay is discussed within experimental and calculated level systematics. Alpha-rays with energy 4.55(2) MeV were assigned to¹⁶⁷W.     

Alpha-particle decay of 218Th,a new isotope

A new isotope, ₉₀²¹⁸Th₁₂₈, has been found to decay with E_α = 9.67 ± 0.02 MeV and $\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 96 ± 7}\text{ns}$. The reduced α-particle width of ²¹⁸Th is about 1.4 times the value expected from the general trend of the N = 128 isotones with Z = 84?89.     

A new neutron-deficient isotope, 235Am

The new transuranium neutron-deficient isotope ²³⁵Am was produced by bombarding of ²³⁸Pu with 35-MeV protons beam via the (p,4n) reaction. The reaction products were transported by a helium-jet system. A rapid radiochemical method was employed for separating the americium isotopes from the complex products. From the observed Kx-rays of Np, γ-ray of ²³⁵Pu and x-γ coincidence measurements, the new neutron-deficient isotope ²³⁵Am with a half-life 15±5min was definitely identified for the first time.