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1.
New neutron-deficient isotopes 188,189Po have been produced in the complete fusion reaction of 52Cr ions with a 142Nd target at the velocity filter SHIP. The evaporation residues were separated in-flight and subsequently identified on the basis of α-γ and α-conversion electron coincidence measurements and of α-α position and time correlations. In 189Po a ground state to ground state α decay with Eα1= 7540(20) keV, T1/2= 5(1) ms and two fine structure α-decays at Eα2= 7264(15) keV and Eα3= 7316(15) keV have been observed. In 188Po (T1/2= 400+200 −150μs) a ground state to ground state α decay at Eα= 7915(25) keV and a fine structure α decay at Eα= 7350(40) keV have been found. Improved data on the α-decay of 189Bi were obtained. Received: 15 October 1999  相似文献   

2.
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 isotopes173, 174Au,175, 176Hg, 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.  相似文献   

3.
Neutron-deficient francium isotopes were produced by proton-induced spallation reactions and investigated by alpha spectroscopy following on-line mass separation. The new isotopes201, 202Fr were identified and their half-lives measured. An improved value for the half-life of203Fr was obtained. Alpha branching ratios were determined for198m, g, 199At. The derivation of the mass excess of202Fr and the systematics of alpha energies and reduced widths are discussed.  相似文献   

4.
Three neutron-deficient isotopes of tungsten have been produced by the reactions of 24Mg on targets of 147Sm and 144Sm. They are 164W, Eα = 5.153 MeV, T12 = 6.3 s; 163W, Eα = 5.385 MeV, T12 = 2.5 s; and 162W, Eα = 5.53 MeV, T12 < 0.25 s.  相似文献   

5.
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 Eα and the half-life T1/2 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 Eα = (7577±20) keV and T1/2 = (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 Eα = (7860±60) keV and T1/2 = (0.7 ?0.3 +3.3 ) ms were measured. Improved decay data have been obtained for 204Ra. The results are Eα = (7484±10) keV and T1/2 = (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).  相似文献   

6.
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 Eα and the half-life T1/2 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 Eα = (7577±20) keV and T1/2=(1.1 ?0.5 +5.0 ) ms to203g 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 Eα = (7860±60) keV and T1/2=(0.7 ?0.3 +3.3 ) ms were measured. Improved decay data have been obtained for204Ra. The results are Eα = (7484±10) keV and T1/2=(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).  相似文献   

7.
Neutron-deficient osmium and rhenium isotopes were produced by bombarding an enriched144Sm target with beams of27Al and28Si. Previously reported decay data concerning168,169,170Os were confirmed. Three newα groups, observed in the144Sm+27Al reaction, were assigned to the decay of166,167,168Re 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 in168,169Re. Our measured data for the isomeric states are: $$\begin{gathered} {}^{168m}\operatorname{Re} , E_\alpha = 5,250 (10) keV, T_{1/2} = 6.6 (15) s and \hfill \\ {}^{169m}\operatorname{Re} , E_\alpha = 5,050 (10) keV, T_{1/2} = 12.9 (11) s. \hfill \\ \end{gathered} $$   相似文献   

8.
Very neutron-deficient isotopes in the trans-tin region were produced by reactions of 290 MeV 58Ni ions on 58Ni targets, and studied by on-line mass separation at GSI. Twelve α-emitters — 107–110Te, 110–113I, 111–113Xe, 114Cs — were identified. Systematics of Qα values and reduced α-widths for this new island of α-emission are discussed.  相似文献   

9.
The proton decays \(\tilde p\) of isobaric analog states of207, 208Pb in the reactions207, 208Pb(p, n) have been studied using a neutron-proton coincidence technique. The width anomaly observed in (p, n) [4] and (p, n \(\tilde p\) ) singles spectra [11] is resolved in the coincident spectra.  相似文献   

10.
The first observation of the extremely neutrondeficient nucleus172Au is reported, produced using the fusion evaporation reaction70Ge+106Cd→176Hg* (Ex?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 %.  相似文献   

11.
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.  相似文献   

12.
Very neutron deficient isotopes in the Hf-Re region were produced by bombarding targets of107, 109Ag,nat, 108, 110Pd, and103Rh with58Ni accelerated by the linear accelerator UNILAC at GSI. After separation from the projectile beam by the velocity filter SHIP, the fusion products were implanted with their full recoil energy into a silicon surface barrier detector. The subsequent alpha decay of the implanted ions was measured with the same detector. In some of the experiments the evaporation residues were implanted into a position sensitive silicon surface barrier detector. With a newly developed position and time correlation technique parent daughter relationships, half lives, andα branching ratios of a large number of isotopes could be determined. In the investigated reactions the eleven new isotopes161–164Re,160W,157–161Ta, and156Hf could be identified. The measuredQ α values, half lives, and a branching ratios are discussed. Two new high energyα. transitions of (7,408±10) keV and (7,804±15) keV were also found with half lives of 2.7 ms and 0.52 ms, respectively.A tentative mass and atomic number assignment givesA=153–156 andZ=70–72. The energies of the excited isomeric states are between 2 MeV and 3 MeV. From the systematics of alpha ground state transitions in even nuclei a hindrance of 105 can be deduced for both transitions, possibly indicating orbital angular momenta on the order of 10? for the alpha emitting states. The isomers are proposed to belong to shell model isomers beyond146Gd.  相似文献   

13.
14.
An enriched sample of 247Cm (99.4 %) has been used to investigate the -decay scheme of 247Cm. Seven -groups with energies and intensities 5.265 (13.8 %), 5.210 (5.7 %), 5.145 (1.2 %), 4.983 (2.0 %), 4.941 (1.6 %), 4.868 (71.0 %) and 4.818 (4.7 %) were observed. Gamma-singles and γ coincidence spectra showed the presence of 278.0, 287.5, 346.0 and 402.4 keV γ-rays. A two-parameter coincidence experiment established that the sources of the 402.4 and the 287.5 keV γ-rays were 4.868 and 4.983 MeV -groups, respectively. The multipolarity of the 287.5 keV transition was found to be M1. The K conversion coefficient of the 402.4 keV γ-ray indicates an E1 multipolarity for this transition. The levels at 287.5 and 402.4 keV have been assigned to the and Nilsson states, respectively. The half-life of 247Cm was found to be (1.56±0.05) ×107 y from the pulse analysis and mass spectrometric analysis of the sample.  相似文献   

15.
Inelastic proton scattering on 206Pb, 207Pb and 208Pb through isobaric analog resonances has been used to study neutron particle-hole excitations with large ground-state γ-branches in these Pb isotopes. Relative (p, p′) cross sections at 90° are extracted for structures selectively excited on the d52, s12and d32?g72 resonances. Interpretation of excitations is 206Pb and 207 Pb in terms of coupling to states in 208Pb is discussed. Branching ratios for 1?states in 208Pb at 4.84, 5.29, 5.94 and 6.31 MeV and the 12+ state in 207Pb at 4.63 MeV are deduced.  相似文献   

16.
We measured for the first time the α decay of 114Ba. The results are discussed in comparison with theoretical predictions.  相似文献   

17.
Theoretical α spectroscopic amplitudes are calculated in jj coupling and isotopic spin formalism. The formulae obtained are applied for calculating the α reduced width amplitudes of the lowest lying 2+ levels of 16O using the shell-model wave functions of Zuker, Buck and McGrory.  相似文献   

18.
Heavy-ion fusion reactions 48Ca + 204Pb and 44Ca + 208Pb leading to the same compound nucleus 252No* were run in attempts to produce new neutron-deficient spontaneous-fission isotopes of 249,250No using the electrostatic separator VASSILISSA. Production cross-sections for the spontaneous-fission activities with the half-lives 5.6 and 54 μs observed in these reactions are compared with the measured ones for the well-known isotopes of 251 - 255No formed in the heavy-ion fusion reactions 48Ca + 206Pb and 48Ca + 208Pb. The obtained excitation functions for the reaction products formed after the evaporation of 1-4 neutrons from the corresponding compound No nuclei have been compared with similar data obtained earlier and results of statistical model calculations. Received: 26 July 2002 / Accepted: 5 November 2002 / Published online: 18 March 2003 RID="a" ID="a"e-mail: eremin@sunvas.jinr.ru Communicated by J. ?yst?  相似文献   

19.
20.
Gamma rays in the disintegration of208Tl(ThC″) have been studied with Ge(Li)-Na I(Tl) anti-Compton and coincidence spectrometers. Several new transitions are reported most of which are placed in a decay scheme incorporating excited states in208Pb at 2,614.5, 3,197.6, 3,475.0, 3,708.3, 3,919.8, 3,960.9, 3,998.5, 4,125.3, 4,180.4, 4,296.1 and 4,480.0 keV. According to the present data, the recently reported intensity of 4.5±1.5% of beta groups feeding levels near 4.3 MeV is far too large.  相似文献   

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