Proton spectroscopy beyond the drip line near<i>A</i>=150

Sellin, P.J.; Woods, P. J.; Davinson, T.; Davis, N.J.; Livingston, K.; Page, R. D.; Shotter, A.C.; Hofmann, S.; James, A.N.

doi:10.1103/physrevc.47.1933

Cited by 79 publications

(55 citation statements)

References 28 publications

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“…The peak contains 43 counts, corresponding to a cross section of approximately 200 nb (assuming a separator efficiency of 3%). This is lower than typical p3n cross sections observed in our recent studies in the region 69 < Z < 75 [2], reflecting the higher degree of fission competition. An energy calibration was obtained from known alpha decay lines 0~~…”

Section: Pacscontrasting

confidence: 68%

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Alpha decay of the new isotope172Au

Sellin

Woods

Davinson

et al. 1993

Z. Physik A - Hadrons and Nuclei

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Abstract:The first observation of the extremely neutrondeficient nucleus XTZAu is reported, produced using the fusion evaporation reaction 7~176(E~ _~ 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 of ~2Au was measured with an energy E,~ = 6860:5 10 keV, corresponding to Q,~ = 7020:5 10 keV, and a half-life of 4:5 1 ms. No evidence was seen for a proton decay branch, implying a limit of bp < 2 %. 23.60. + e; 23.90. + w; 27.70. + q Direct proton emission has now been established from extremely neutron-deficient odd-Z nuclei between Tm (Z=69) and Re (Z---75) [1,2,3]. In order to extend the region of proton emission data further towards heavier elements, we have carried out a search for the proton decay of the previously unknown nucleus 172Au. Various mass models predict a positive proton decay Q-value for this nucleus, although the degree of competition from alpha decay is critically dependent on both the precise decay Q-values and nuclear structure effects. PACS:Evaporation residues from the reaction 7~176 were implanted into a double-sided silicon strip detector positioned at the focal plane of the Daresbury recoil mass separator [4]. Over a period of 48 hours a 2 nA (particle) beam of 354 MeV 7~ ions was used to bombard a 500 #g cm -2 thick target of 80% isotopically enriched a~ backed by a 20 #g cm -2 thick carbon foil. The compound nucleus was produced with a mean centre--of-target excitation energy _~ 64 MeV in order to maximise the yield of lr~Au via the p3n evaporation channel. The recoil mass separator was adjusted to position evaporation residues with mass numbers A= 171-175 onto the strip detector. Figure 1 shows the resulting decay spectrum which contains a new alpha decay line at an energy above that of the lightest known gold isotope 173Au (Ec~ = 6720:5 20 keV [5]). This activity occurs within the A=172 region of the strip detector and is assigned to ~72Au on the basis of alpha decay Q-value * Present address: Department of Physcis, University of Sheffield, Sheffield $3 7RH, UK systematics. The peak contains 43 counts, corresponding to a cross section of approximately 200 nb (assuming a separator efficiency of 3%). This is lower than typical p3n cross sections observed in our recent studies in the region 69 < Z < 75 [2], reflecting the higher degree of fission competition. An energy calibration was obtained from known alpha decay lines 0~~151'1~1mHO, 152Er, lSSyb and 156Lu [6,7]) of residues implanted into the detector, giving a decay energy for the new peak of E~ = 6860 4-10 keV with a corresponding alpha decay Q-value of Q~ = 7020 • 10 keV. The half-life of 1T2Au was measured from the time difference between correlated implantation and decay events, giving a value of t_~ = 4 + 1 ms. This corresponds to a reduced alpha decay widt]a, assuming a Al = 0 transition and b,~ = 100 %, of 1.3+~ relative to the alpha decay of 212Po. The measured alpha decay Q-values of lig...

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Section: Pacscontrasting

confidence: 68%

“…+ w; 27.70. + q Direct proton emission has now been established from extremely neutron-deficient odd-Z nuclei between Tm (Z=69) and Re (Z---75) [1,2,3]. In order to extend the region of proton emission data further towards heavier elements, we have carried out a search for the proton decay of the previously unknown nucleus 172Au.…”

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confidence: 98%

Alpha decay of the new isotope172Au

Sellin

Woods

Davinson

et al. 1993

Z. Physik A - Hadrons and Nuclei

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“…This causes a large uncertainty in the proton decay rate, making comparison with theory difficult. In the case of 150 Lu the ground state has a proton decay branch which is relatively long lived (E p =1.216͑4͒ MeV, t 1/2 =35͑10͒ ms [4] and t 1/2 =49͑5͒ ms [5]), which limits the precision of the derived proton decay partial half-life. A new short-lived isomeric state was reported, however it has large uncertainties in the energy and the half-life [E p =1.295͑15͒ MeV, t 1/2 =30 −15 +95 s] [5].…”

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confidence: 99%

Proton decay study ofLu150andLum
Robinson
¹
,
Mukherjee
²
,
Seweryniak
³

et al. 2003
Phys. Rev. C
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150 Lu was produced via the 1p3n fusion-evaporation channel by bombarding a 96 Rn target with a 297-MeV 58 Ni beam, evaporation residues were analyzed using the fragment mass analyzer at Argonne National Laboratory. A new delay-line amplification system was used to make a new more precise measurement of proton decay from the isomeric state in 150 Lu [E p =1.286͑6͒ MeV, t 1/2 =52.5 −8.7+13 s]. In addition the half-life of the proton emitting ground state was measured to be 43(5) ms. Proton decay partial half-lives for both transitions are compared with theory. The isomeric transition is found to have a significantly smaller spectroscopic factor than the h 11/2 ground state transition.While great progress has been made in understanding the decay rates of spherical [1,2] and deformed odd-A proton emitters the situation for odd-odd proton emitters is not so clear [3]. Accurate information is needed on transitions in odd-odd nuclei to provide stringent tests of new theoretical calculations of proton decay rates from odd-odd nuclei [3]. In many cases of proton decay from odd-odd nuclei, the ␤-decay branches are unknown, but are expected to be comparable in size to the proton branch. This causes a large uncertainty in the proton decay rate, making comparison with theory difficult. In the case of 150 Lu the ground state has a proton decay branch which is relatively long lived (E p =1.216͑4͒ MeV, t 1/2 =35͑10͒ ms [4] and t 1/2 =49͑5͒ ms [5]), which limits the precision of the derived proton decay partial half-life. A new short-lived isomeric state was reported, however it has large uncertainties in the energy and the half-life. The present paper describes new measurements for the proton decays from the ground and isomeric states in 150 Lu. In particular, a new delay-line amplification system has been employed to improve the energy and the time response to short-lived proton decays in order to provide a more precise comparison of the proton decay rates with theoretical models.The standard proton decay setup for use at the Argonne fragment mass analyzer (FMA) has been described elsewhere [1]. In the present experiment a new design 60-m thick, 80ϫ80 double sided strip detector (DSSD) with a strip pitch of 400 m, was situated behind the focal plane of the FMA [6]. As usual the DSSD was instrumented with semiGaussian shaping amplifiers and charge-sensitive preamplifiers [7]. However, the observation of proton emission on a microsecond time scale is problematic. Following an evaporation residue implant signal the shaping amplifiers have an initial dead time period of 0-7 s. If a decay proton event occurs in the following overload recovery period ͑7-25 s͒ the energy measured for the proton will include the tail of the overload pulse. Thus short-lived decays with half-lives in the microsecond range will have energies depending on the time of decay. This latter effect can be reduced but not entirely eliminated by the insertion of degrader foils in front of the DSSD to lower the energy of the implanted ion. This behavior is illustr...

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“…This effect has been observed directly in the proton [34], and the corresponding lowspin proton emitting isomers 151m Lu [35] and 150m Lu [36] the more exotic odd-odd nucleus has nearly the same proton decay energy as its odd-even less exotic partner. The information on the odd-Z isotopes gathered near 100 Sn shows a strong staggering of the proton separation energy, such that for Cs and I the odd-odd emitters have smaller decay energy than their neighbors.…”

Section: Odd-even Effect and Theoretical Calculationsmentioning

confidence: 99%

Experimental study of the decays of112Cs and111Xe

et al. 2012

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An experiment to search for the alpha decay of 112 Cs has been performed at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. The alpha decay of 112 Cs was not observed, thus setting the upper limit of the alpha branching ratio at 0.26%. The half-life of 112 Cs was measured as 506 ± 55 µs. In the same measurement the decay properties of its proton decay daughter 111 Xe were also reinvestigated. The newly measured alpha branching ratio for 111 Xe is 10.4 ± 1.9 %. The experimental proton separation energies Sp for odd-Z nuclei above 100 Sn were compared to shell model calculations. The calculated proton separation energies for 103 Sb and 102 Sb point to half-lives of the order of 10 ps and 1 ns, respectively.

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Proton spectroscopy beyond the drip line nearA=150

Cited by 79 publications

References 28 publications

Alpha decay of the new isotope172Au

Alpha decay of the new isotope172Au

Proton decay study ofLu150andLum
Robinson
¹
,
Mukherjee
²
,
Seweryniak
³

et al. 2003
Phys. Rev. C
Self Cite
21
1
4
0
View full text Add to dashboard Cite

Experimental study of the decays of112Cs and111Xe

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Proton spectroscopy beyond the drip line nearA=150

Cited by 79 publications

References 28 publications

Alpha decay of the new isotope172Au

Alpha decay of the new isotope172Au

Proton decay study ofLu150andLumRobinson1, Mukherjee2, Seweryniak3 et al. 2003Phys. Rev. CSelf Cite21140View full textAdd to dashboardCite

Experimental study of the decays of112Cs and111Xe

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Proton decay study ofLu150andLum
Robinson
¹
,
Mukherjee
²
,
Seweryniak
³

et al. 2003
Phys. Rev. C
Self Cite
21
1
4
0
View full text Add to dashboard Cite