Note on the decay of200Au

Gamma and beta rays from the decay of²⁰⁰Au (48.4 min) were studied employing Ge(Li) and plastic detectors in various singles and coincidence arrangements. The intensity of the β-branch to the ground state of²⁰⁰Hg was determined as 79%, and the disintegration energy of²⁰⁰Au to be asQ _β=2.26 ± 0.06 MeV. A tentative spin and parity assignment of (1,2)⁺ is proposed for levels at 1515.2 and 1972.5 keV in 200_Hg     

The charge radii of198Pt-183Pt

The reactions⁵⁸Ni+¹⁰²Pd→¹⁶⁰W and⁵⁸Ni+¹⁰⁶Cd→¹⁶⁴Os were investigated to search for new decay data of neutron deficient nuclei. Excitation energies of the compound nuclei covered a range from 47 to 89 MeV. Velocity separation of the evaporation residues and position time correlations with the a decays of the implanted nuclei were used. The following new decay data were measured:¹⁶²Os (E_α=(6611 ±30) keV, T_1/2=(1.9±0.7) ms);¹⁵⁸W (T_1/2=(0.9±0.3) ms);¹⁵⁸m_W (E=1.88 MeV, E_α=(8280±30) keV, T_1/2=(0.01-1) ms);^155mLu (E_α=(5575±10) keV); β decay of¹⁵⁶Ta (T_1/2 > 10 ms) to the 8⁺ yrast isomer in¹⁵⁶Hf. A cross section of 5μb was measured for the new isotope¹⁵⁶Ta produced in a p3n evaporation channel from¹⁶⁰W at 64 MeV excitation energy.     

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.     

Electron capture decay of 51 min191Hg

The decay¹⁹¹Hg→¹⁹¹Au was investigated by measuring γ-ray spectra, conversion electron spectra, and coincidence spectra, as well as lifetimes in the second region. The parent isotope¹⁹¹Hg was produced by the reaction¹⁹⁷Au (d, 8n) withE _d =80 MeV. About 80 γ-transitions of this decay were observed. Multipolarities of the more intense transitions were determined. An isomeric state of 0.92±0.11 s half-life was found in¹⁹¹Au. A level scheme for¹⁹¹Au is suggested. The measured γ-transitions are attributed to the decay of a 13/2⁺ isomeric state of¹⁹¹Hg; its half-life was found to be 50.8 ±1.5 min. The core excitation model was used to discuss some features of the level structure in¹⁹¹Au.     

Alpha decay of new neutron deficient gold,mercury, and thallium isotopes

In fusion evaporation reactions of a⁹²Mo beam with targets of neutron deficient Rb — Mo isotopes very neutron deficient isotopes of elements between Au and Po have been produced. The new isotopes^{173, 174}Au,^{175, 176}Hg, and¹⁷⁹Tl were identified by alpha spectroscopy. The mass excess value of¹⁷⁶Hg could be linked to known values of theN?Z=16 chain. The location of the new isotopes with respect to the proton drip line is discussed. A new high energyα transition of (7.20±0.02) MeV andT _1/2=(1.4±0.5) ms has been found in the reaction⁹²Mo+⁸⁹Y→¹⁸¹Tl^* at an excitation energy of 37 MeV. It is tentatively assigned to isotopes produced in 2-particle evaporation channels.     

Structure of140Pm from beta decay of140Sm

The structure of¹⁴⁰Pm is investigated through the beta decay of¹⁴⁰Sm, whose half-life is measured to be (14.7 ± 0.2) m. A level structure comprising 41 transitions among 17 excited states is constructed. Using the deduced ft values and measured internal conversion coefficients, spin-parity assignments to several states in¹⁴⁰Pm were made. From beta end-point measurement, the total decay energy is deduced to beQ _EC =3.4±0.3 MeV, which is compared with the predictions of several mass formulae. The systematics of the odd-Z, N=79 isotones are discussed.     

Measurement ofK-electron capture probability (P k ) in the decay of197Hg (64.1 h)

TheK-electron capture probability (P _K ) for the 268.7 and 77.3 keV states of¹⁹⁷Au in the decay of¹⁹⁷Hg (64.1h) have been determined from theKX-ray gamma ray summing in a HPGe X-ray detector. The measured values,P _k (268.7)=0.746±0.033 andP _k (77.3)=0.774±0.036 are found to be in good agreement with the theoretical results.     

Der Zerfall des125m Xe,des127m Xe und des127g Xe

The decay of^125m Xe produced by the reaction¹²²Te(α, n)^125m Xe using a target enriched in¹²²Te (95.4%) and the decay of^127m Xe produced by the reaction¹²⁷J(d, 2n)^127m Xe have been investigated: ^125m Xe decays with a half-life ofT _1/2=(56±3) sec by ayy- cascade withE _γ1=(140.4 ±0.5) keV andE _γ2=(110.5 ±0.5) keV. The experimental conversion coefficients yield multipolarities ofE3 for the 140.4 keV isomeric transition and predominantlyM1 for the 110.5 keV-transition. ^127m Xe decays with a half-life ofT _1/2=(71±2) sec. The decay also proceeds by aγγ-cascade with an isomeric E3 transition ofE _γ1=(172.5±0.3) keV and a predominantlyM1 transition ofE _γ2=(124.6±0.3) keV. In the decay of^127g Xe an additional branching of the electron capture to a level at (618.1±0.3) keV was observed. The relative probability forK-captureP _K618/P_K375=0.40 ±0.07 yields a total transition energyQ _EC=(664 ±4)keV. A spin of 1/2⁺ was assigned to the ground state.     

Identification of153Lu β decay

In the bombardment of a 270μg/cm ^{2 180}Hf target with⁴⁸ Ca projectiles at a primary beam energy of E/A=4.24 MeV/u the new nuclide²²⁵U was produced. The experiment was performed at the velocity filter SHIP. ²²⁵U was found to decay by α emission with E_α=(7880 ±20) keV (≈90%), (7830±20) keV (≈10%) and has a half-life ofT _1/2=(80 _?20 ⁺⁴⁰ ms).     

Reactions of 40Ar with 159Tb, 142Nd and 144Sm; New α-activities from 189Bi, 173Pt and 177Au

Reactions of ⁴⁰Ar ions with targets of ¹⁵⁹Tb, ¹⁴²Nd, and ¹⁴⁴Sm have been studied at energies below 300 MeV with a helium gas-jet system. Excitation functions for (Ar, xn) reactions, where x = 5–10, were obtained for the radioactive products that decay by α-emission. Based on the characteristics of these excitation functions and on the systematics of α-decay, evidence is presented for the existence of the nuclides ¹⁸⁹Bi with α-particle energy E_α = 6.67±0.01 MeV and half-life < 1.5 sec, and ¹⁷³Pt with E_α = 6.19±0.01 MeV; and for the emission from ¹⁷⁷Au of an α-particle with E_α = 6.15±0.01 MeV.     

Perturbation of the decay rate of90m Nb by implantation in metals

The perturbation of the decay constant of^90m Nb implanted in various transition metals (Zr, Nb, Hf, Ta, Ag and Au) has been determined by direct half-life measurements. Particular care was taken to evaluate and minimize possible systematic errors. The maximum relative change found is ν_Au?ν_Nb/ν_Nb=(4.5±0.8)%     

Structure of even-even138Nd from the decay of138Pm

The structure of¹³⁸Nd is investigated through theβ ⁺-decay of¹³⁸Pm, whose decay half-life is measured to be 3.24±0.05 min. A level structure comprising 27 excited states and 52 transitions is constructed. With the help of deducedft values and internal conversion coefficients, spin-parity assignments are made to many states in¹³⁸Nd and to the ground states of¹³⁸Pm. From the positron end-point energy measurement, the total decay energy is determined to be 5.4±0.2 MeV, which is compared with the predictions of several mass formulae and with the decay energy systematics of theN=77 isotones. The structure of¹³⁸Nd is discussed in the light of nuclear systematics of theN=78 isotones.     

The decay of 31 sec98Zr, 2.9 sec98Nb and 51 min98Nb

TheΒ- andγ-radiations of⁹⁸Zr and^{98m, g} Nb have been investigated employing scintillation and semiconductor spectrometers and coincidence techniques. Sources of⁹⁸Nb were produced by the⁹⁸Mo(n, p)⁹⁸Nb reaction, sources of⁹⁸Zr by fission of²³⁵U with thermal neutrons applying chemical separations. For⁹⁸Zr, a half-life of 30.7±0.4 sec and aQ _β-value of 2.3±0.2 MeV were obtained, for the⁹⁸Nb isomers, half-lives of 2.86±0.06 sec and 51.3±0.4 min, andQ _β-values of 4.8±0.2 MeV and 4.5±0.2 MeV, respectively. Noγ-rays were observed in the decay of⁹⁸Zr. The decay of 2.9 sec⁹⁸Nb was found to involve 11γ-ray transitions. In the decay of 51 min⁹⁸Nb, 54γ-transitions were detected. Spin and parity of 1⁺ and 4^? were deduced for the isomeric states of⁹⁸Nb.     

Q EC value and Gamow-Teller strength of the102CdEC/gb+ decay

Within the framework of a systematic study of 0⁺→1⁺ Β-transitions in the¹⁰⁰Sn region, the decay of the neutrondeficient isotope¹⁰²Cd was investigated. This isotope was produced in¹⁶O+⁹²Mo and⁵⁸Ni+⁵⁰Cr heavy-ion reactions and in proton-induced spallation of^natSn, and mass-separated samples were prepared by means of the GSI and the ISOLDE on-line mass separators, respectively. Observations of X-rays,γ-rays, and conversion-electrons studies have led to an improved¹⁰²Cd→¹⁰²Ag decay scheme which includes six 0⁺→1⁺ Gamow-Teller transitions. The half-life of¹⁰²Cd was redetermined with higher accuracy to be 345±8 s. Using a Si(Li)-BGO-Ge spectrometer, theΒ ⁺ endpoint energy of the main decay component was measured, yielding aQ _EC value of 2587±8 keV. This very small uncertainty ofQ _EC, combined with the improved knowledge of half-life and decay scheme, allows an accurate determination of the observed Gamow-Teller decay strengthB _Σ (GT)=1.513±0.055 for¹⁰²Cd. This result is discussed in comparison with predictions from model calculations.     

Decay of194Os andL 1 subshell yields atZ=77

The relative intensities of x rays and gammas emitted in the beta decay of¹⁹⁴Os are measured. No evidence for the feeding of a level at 83 keV in¹⁹⁴Ir is found. An upper limit of 1.7×10^?4 was set for theK shell internal ionization probability in the beta decay to the ground state of¹⁹⁴Ir. TheL-conversion coefficient of 43 keV transition is found to be 12.1 and the transition is mainly ofM1 type with an admixture of 1.3%E2 type. TheL ₁ subshell yields atZ=77 are determined to beω ₁=0.16±0.04,f ₁₂=0.11±0.04 andf ₁₃=0.37±0.03.     

Der Zerfall des 2,4-sec100Nb

The nuclide¹⁰⁰Nb was produced by irradiation of enriched¹⁰⁰Mo targets with 14 MeV-neutrons, and its decay properties were investigated employing scintillation and semiconductor spectrometers and coincidence techniques. A half-life of 2.4±0.3 sec and aQ _β-value of 5.8±0.2 MeV were found. From 27 gamma-rays, 20 transitions, representing 95% of the observed gamma-ray intensity, could be placed in a decay scheme comprising 10 excited states of¹⁰⁰Mo.     

A study of excited states of5He by the7Li (d, α)5He-reaction

The interactions of deuterons with⁷Li, in which two α-particles and a neutron are produced in the final state are studied atE _d =1.2 MeV. The dual parameter α-α coincidence spectrum was analyzed with a search program. The results indicate two excited states of⁵He: One at excitation energy 2.9±0.1 MeV and with a reduced width of γ²=1.1±0.4 MeV, and the other at 4.8±0.4 MeV, with γ²=0.9±0.4 MeV. No contributions of sequential decay through the 4⁺ state in⁸Be or direct three body decay was observed.     

Konversionskoeffizient von69m Zn und Fluoreszenzausbeute von Zink

The decay of^69m Zn and⁶⁹Zn has been investigated using a radioactive source obtained by irradiating a sample of 99%⁶⁸ZnO with neutrons. Theβ-spectrum of⁶⁹Zn and the conversion electrons of the^69m Zn decay have been studied with an anthracene scintillation spectrometer of the split crystal type. The measured value of the conversion coefficient of^69m Zn is α=0.054±0.003. With this result and those obtained by measurement of theγ-ray spectra of^69m Zn with NaI(Tl) scintillation crystals, theK-fluorescent yield of Zn has been determined to be ω_K=0.45±0.04.     

Anomalous conversion of 127 keV (E3) transition in134Cs

The total conversion coefficient of the 127.49 keV E3 isomeric transition in the decay of^134mCs was measured using the gamma intensity balance method with the help of a high resolution low energy photon detector. Theα _Tvalue was found to be 5.84±0.47 as against the theoretical value of 6.96, thus showing an anomaly of (16.1±6.7)%. TheK-conversion coefficient,α _kwas also measured using the X-ray peak to gamma ray intensity method and found to be 2.24±0.04 as against the theoretical value of 2.72, which shows an anomaly of (17.6±1.4)% consistent with the experimental anomaly inα _T. TheE3 hindrance factor of the isomeric transition was estimated to be (3.44±0.23) ·10⁴.     

Excitation function for the production of 265108 and 266109

The excitation function for the production of²⁶⁶109 by the reaction ⁵⁸Fe + ²⁰⁹Bi was investigated. Its position and width could be reproduced using the same values (E* = 13.9 MeV; FWHM=4.8 MeV) as inthe case of²⁶⁵108 produced by the reaction ⁵⁸Fe + ²⁰⁸Pb. A cross-section maximum of (7.5 ± 2.7) pb was obtained. Referred to ²⁶⁵108, this value is reduced by a factor of 8.8 ± 3.3, that is more than the average reduction of cross-section by 3.7 per element. The hindrance factor of 2.4 ± 0.9 could be due to a specialization energy in the fusion process by the unpaired proton of ²⁰⁹Bi in the h_9/2 orbital. A total of twelve decay chains of ²⁶⁶109 was measured, resulting in a mean half-life of ( _1.7?0.4 ^+0.6 ) ms. The new data confirm the decay data of the previously measured two decays of ²⁶⁶109.