Alpha decay of the new isotope172Au

The first observation of the extremely neutrondeficient nucleus¹⁷²Au is reported, produced using the fusion evaporation reaction⁷⁰Ge+¹⁰⁶Cd→¹⁷⁶Hg^* (E_x?64 MeV). Mass separated evaporation residues were implanted into a double-sided silicon strip detector, and the energy and time of subsequent decay events were recorded. The alpha decay of¹⁷²Au was measured with an energy =6860±10 KeV, corresponding to =7020±10 Kev, and a half-life of 4±1 ms. No evidence was seen for a proton decay branch, implying a limit ofb _p ≤ 2 %.     

Alpha decay of the new isotope 174Hg

Neutron deficient mercury isotopes were produced in the reaction ³⁶Ar + ¹⁴⁴Sm using bombarding energies of 180–230 MeV. Fusion products were separated in-flight from the primary beam using a gas-filled recoil separator. An alpha line with the alpha particle energy and half-life of (7069±11) keV and (2.1 _?0.7 ^+1.8 ) ms, respectively, was assigned to the new mercury isotope ¹⁷⁴Hg.     

The radioactive decay of 170Re

A new, highly neutron deficient isotope, ¹⁷⁰Re, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 8.0±0.5}\text{s}$, has been produced via the ¹⁵⁹Tb(²⁰Ne, 9n) reaction at beam energies of 180 MeV. The helium-jet transport technique was used to study the decay. Results from singles and coincidence γ-ray spectroscopy are reported.     

The decay of 20 min179Re

The decay of 20 min¹⁷⁹Re has been studied by means of Ge(Li) and Si(Li) detectors and a magneticβ-ray spectrometer. From the measured positon endpoint aQ-value of 2690±50 keV has been deduced. The decay scheme given is supported by coincidence relations. Fast beta transitions (logft≈5.1) to levels at 720keV and 1680 keV in¹⁷⁹W can be explained by a three quasi-particle character for these states. Nilsson assignments to these and other levels are discussed.     

The new isotope 270110 and its decay products 266Hs and 262Sg

The even-even nucleus ²⁷⁰110 was synthesized using the reaction ⁶⁴Ni + ²⁰⁷Pb. A total of eight α-decay chains was measured during an irradiation time of seven days. Decay data were obtained for the ground-state and a high-spin K isomer. The new nuclei ²⁶⁶Hs and ²⁶²Sg were identified as daughter products after α-decay. Spontaneous fission of ²⁶²Sg terminates the decay chain. The measured data are in agreement with calculations using the macroscopic-microscopic model and with self-consistent HFB calculations with Skyrme-Sly4 interaction. Received: 27 November 2000 / Accepted: 16 January 2001     

Gamma-radiation in the183Re decay

The gamma-ray intensities have been determined by means of Ge(Li) detectors. The previously proposed decay scheme has been tested using Ge(Li)- spectrometers. It has been found that the experimental data are not in disagreement with foregoing decay scheme. The comparison of the theoretical (if the Coriolis interaction is taken into account) and experimental gamma line intensity ratios is given.     

The decay of the new isotope180Yb and the search for ther-Process path to180mTa

Irradiating^natW/Ta targets with¹⁸⁶W, the decay of the new isotope¹⁸⁰Yb was observed and its half-life determined to be 2.4(5) min. Based on the measuredβ-,γ- and X-ray data, ther-process production of^180mTa and the role of a possible isomer^180mLu in this context are discussed.     

Radioactive decay of Re188

The spectra of negatons, conversion electrons and photoelectrons were measured with the iron-yoke double focusing spectrometer. Two-groups with end-point energies 2128 and 1973 keV andlgf values 8.04 and 8.41 respectively were observed. TheK andL conversion coefficients of 155.0 keV transition were found to be in agreement with theoretical prediction within a few per cent. Three new-transitions, 635, 1175 and 1461 keV, were observed and some corrections of the decay scheme were made. The possible interpretations of the excited states are discussed.     

Theβ + decay of the new isotope86Mo and the first observation of86m Nb

Theβ ⁺ decay of⁸⁶Mo has been firstly investigated by means ofβγ spectroscopy. The⁸⁶Mo nuclei were produced by fusion-evaporation reactions of⁵⁴ Fe (³⁵Cl, 1 p2n) and⁵⁸Ni (³²S,2p 2n) at beam energies of 103 and 120 MeV, respectively. Threeγ rays of 47.3, 49.8 and 187.0 keV were unambiguously identified to follow theβ ⁺ decay of⁸⁶Mo by results ofXγ andβγ coincidence and cross-bombardment. A half life and a maximumβ ⁺-ray energy of⁸⁶Mo were determined to be 19.6±1.1 s and 3.9±0.4 MeV, respectively. A decay scheme of⁸⁶Mo is proposed in this article. Furthermore, a decay of⁸⁶Nb has been studied using the same combinations of projectiles and targets, and a newβ-decaying isomer^86m Nb was observed with a half life of 56.3±8.3 s.     

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.     

Nuclear orientation study of the decay of 171Lu

The levels and γ-ray transitions in ¹⁷¹Yb have been studied by radioactive decay of oriented ¹⁷¹ Lu. The orientation was produced using the hyperfine field in ferromagnetic gadolinium to polarize an ensemble of ¹⁷¹Lu nuclei at a temperature of 14mK. The directional distribution of the γ-rays was measured using high-resolution Ge(Li) detectors. Anisotropies of 30 γ-rays in ¹⁷¹Yb were measured. Multipole mixing ratios were deduced for most of the mixed γ-ray transitions and unambiguous spin assignments were made for several levels.The energy and structure of the rotational band levels, reduced E2 and M1 transition probabilities and E2/M1 mixing ratios were calculated using the semi-microscopic quasiparticle-phonon model with a Coriolis interaction. In general, good agreement is obtained between the theoretical predictions and experimental results.     

Investigation of the decay182Re→182W

The single gamma-ray spectrum and gamma-gamma coincidence spectra have been studied in the decay of 64-hour isomer of¹⁸²Re with the aid of large coaxial Ge(Li)-detectors. A total of 14 new gamma-ray transitions have been observed and three new levels introduced. The experimental values of internal conversion coefficients for majority of transitions were determined and conclusions about their multipolarities were drawn. The character of the decay of the investigated¹⁸²Re isomer (64-hour) indicates that it is most probably the p402+n624 7⁺ -state.The authors are indebted to dr. J. Zvolský for helpful discussions and encouragement. Our thanks are due to dr. E. Ryndina who placed the large Ge(Li)-detectors at our disposal, and to dr. V. Fominykh for his help and suggestions with the coincidence circuits used in this research. One of us (P.G.) is grateful to dr. V. Brabec, head of the Nuclear Spectroscopy Department in e, for hospitality during his stay in Prague.     

Gamma-ray investigation of different silver isotope decay

The investigation of different silver isotope decay gamma-rays fromA=102 toA=113 was made using two Ge(Li) detectors with resolution 3·7–6 keV. The results obtained and data from other papers were analyzed to correct and to complete the decay schemes of these nuclei. The radioactivity having a half-time of 3 min. is considered as a new isotope of⁹⁷Ag. Three new states were added to the level scheme of¹⁰²Ag in agreement with the results of the -gamma and gamma-gamma coincidences. Two gamma-ray transitions were added to the scheme of excited levels of¹⁰³Pd. About 60 transitions were found in the decay of the two known isomers of¹⁰⁴Ag. Most of them are located in the decay scheme of the 19 excited levels of the¹⁰⁴Pd isotope. Positive parity was assigned to all of them.The¹¹²Ag and¹¹³Ag gamma-ray spectra were first obtained with the aid of a Ge(Li) spectrometer. The observed transitions were placed in a decay scheme containing 16 levels in the case of¹¹²Cd and 5 levels in the case of¹¹³Cd.The properties of the low excited even-even isotope states of Ru, Pd and Cd are discussed and compared.The authors are deeply indebted to M. K. Nikitin for participation in the chemical separation of a series of samples and to L. F. Protasova for help in the measurements. One of the authors (E.P.G.) expresses his sincere thanks to Prof. V. Petrílka for kindly providing him with excellent conditions for research in Prague.     

Study of Er171 decay by means of an electron-gamma coincidence technique

The decay scheme of Er¹⁷¹ (7.8 h) has been reinvestigated by means of an electron-gamma coincidence spectrometer and a scintillation spectrometer with a transistorized RIDL-400 channel analyser. A careful unfolding of the high energy region of the gamma-ray spectrum revealed the presence of photopeaks at energies of approximately 371, 404, 543, 572, 618, 675, 738, 796, 869, 910 and 962 keV. The existence of 32 transitions in Tm¹⁷¹ was confirmed. Also, it is proved that the 277, 362 keV transitions are in coincidence with the 210 keV and that the 175 keV transition is in coincidence with the 86 keV transition. We revealed the doubt for the existence of the 166, 210, 236, 277 and 419 keV transitions. From coincidence and single counting rates the followingK-conversion coefficients of the 111, 116, 124, 296 and 308 keV transitions were determined to be: α _K (111)=1.561±0.062, α _K (116)=0.699±0.035, α _K (124)=0.608±0.024, α _K (296)=0.0197±0.0010, α _K (308)=0.0183±0.0009, which give the 116, 124 keV transitions an electric quadrupole character; the 111 keV transition a magnetic dipole character withE2/M1 equal 0.4528; and the 296, 308 keV transitions an electric dipole character withM2/E1 equal 0.0058 and 0.0071 respectively.     

Gamma decay of the lowly excited states of 189Re

189W activities were produced via the 192Os(n, α) reaction using irradiation of isotopically enriched 192Os metallic powder of ～100 mg/cm2 with 14 MeV neutrons. The X-γ and γ-γ coincidence measurements were made so as to obtain γ rays from 189W decay and its coincidence relations. A new simple decay scheme of 189W including three γ rays of 210.2, 229.6 and 260.2 keV is proposed. Two new levels of 189Re at 470.4 and 489.8 keV are assigned.     

First observation of the beta decay of117Pd and the discovery of a new isotope119Pd

In this paper we wish to report the first direct observations of the beta decays of¹¹⁷Pd and of a new isotope¹¹⁹Pd. The measuredβ-half-life is 4.3±0.3 s for¹¹⁷Pd. For¹¹⁹Pd, the existence of two beta-decaying states with the same half-life but of opposite parity cannot be excluded. The measured half-life for¹¹⁹Pd is 0.92±0.13 s. The observed beta half-lifes are in good agreement with the QRPA predictions. The observed level structure of¹¹⁷Ag and¹¹⁹Ag are discussed in the frame of the level systematics of the known odd Ag isotopes closer to stability.     

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 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.