Spectroscopy  of  Neutron-­‐‑Deficient  Nuclei  Near  the  Z=82  Shell  Closure

kondev@anl.gov  

       Outline  q   Introduc2on  &  Mo2va2on  q   Symmetric  Fusion  Reac2ons  as  a  tool  for  spectroscopy  studies  q   Recent  results  on  neutron-­‐deficient  179,180Tl  nuclides  using  the  Recoil  Decay  Tagging  technique,  FMA  &  Gammasphere      

q   Outlook  &  Conclusions    

2  

Introduction  &  Motivation

ü  179Tl  is  24  neutrons  away  from  the  stable    203Tl  

proton  emi-er  

ü  tes2ng  ground  for  studying  the  phenomenon  of  shape  coexistence                        interplay  between  microscopic  shell  effects,  such  as  the  occurrence  of  large  gaps  in  the  single-­‐par2cle  energies  and  the  occupa2on  of  high-­‐j  intruder  orbitals  

G.D.  Dracoulis,  Phys.  Scr.  T88  (2000)  54    

188Pb  

K.  Heyde  and  J.L.  Wood,  Rev.  Mod.  Phys.  83  (2011)  1467    

Y.  Litvinov  et  al.,  Nucl.  Phys.  A756  (2005)  3    

A.  Thornthwaite  et  al.,  Phys.  Rev.  C86  (2012)  064315    

q   define  the  mass  surface  at  the  drip-­‐line  

π(h9/2)(oblate)  π(i13/2)(prolate)  π(i13/2)(oblate)  π(d3/2)-­‐1  π(s1/2)-­‐1  

π(h11/2)-­‐1  11/2-­‐  

11/2-­‐  

9/2-­‐  

3/2+  

1/2+  

13/2+  13/2+  

Neutron  Number  

177Tl  

Introduction  &  Motivation  –  cont. q 181-­‐195Tl  –  ü  spherical  ground  state  –  1/2+  (s1/2)  ü  oblate-­‐deformed  isomer  –  9/2-­‐  (h9/2)  ü  prolate-­‐deformed  -­‐    low-­‐Ω, i13/2  orbital  

oblate-­‐deformed  -­‐    high-­‐Ω, i13/2  orbital  

q 177Tl  (N=96)  –  J.L.  Poli  et  al.,  PRC  59  (1999)  ü  spherical  ground  state  –  1/2+  (s1/2)  ü  spherical  isomer  –  11/2-­‐  (h11/2)    q   179Tl  (N=98)  ü  K.  Toth  et  al.,  PRC  58  (1990)  1310    ü  R.  Page  et  al.,  PRC  53  (1996)  660  ü   M.  Rowe  et  al.,  PRC  65  (2009)  054310  ü  A.  Andreyev  et  al.,  JP  G37  (2010)  035102  –  

only  the  decay  of  an  isomer    

?  179Tl  

5  

Neutron-­‐‑deficient  Au  nuclei  (Z=79)

F.G.  Kondev  et    al.,  PLB  512  (2001)  

q  low-­‐J  ground  state/high-­‐J  isomer  q   only  11/2-­‐  state  known  in  175Au  

179Tl  

6  

Experimental  Challenges q   Conventional  Heavy-­‐‑ion  fusion-­‐‑evaporation  reactions  to  get  there,  but  ...

ü  charged  particle  emission  is  significant  –  the  cross  section  is  fragmented  –  lower  yield  of  the  nuclide  you  want

ü  fission  process  (CN  fissility  ~Z2/A1/3  –  180Hg-­‐‑>238U)  -­‐‑  depletion  of  high-­‐‑l  values  –  limit  population  of  states  at  high  spin  -­‐‑  huge  unwanted  background

ü minimizes  the  fission  probability ü  enhanced  fusion  cross  section  -­‐‑  

minimizes  the  fragmentation  of  reaction  channel

q allows: ü   more  beam  on  target ü   less  restrictive  gating

BoPom  line:   you  make  more  of  the  stuff  you  want!

q  Symmetric  reactions  near  the  barrier

Experiments  &  Techniques

PGAC

The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.

ü  90Zr  +  90,92Zr@180Hg  ü  90Zr  +  82Mo@182Pb  ü  89Y  +  90Zr@179Au  ü  84Sr  +  92-­‐96Mo@176-­‐180Hg  ü  89Y  +  92Mo@181Tl@375  MeV                                    X-­‐array  

one  “Super-­‐Clover”  &  four  70  X  70  mm  Clovers  

179Tl:  α-decay  properties

179Tl  

175Au  

171Ir  

g.s.  isomer  

ε+β+11%

ε+β+

22%

179Hg    (1p1n)  

9  

179Tl:  lifetimes

2

5000 6000 7000100

101

102

103

104

105

Eα1 (keV)

Cou

nts 71

946556

6431

6286A=179 gated

0 < Δtα1 < 4 s

FIG. 1: Energy spectrum of first-generation ↵-decay eventswith a requirement that the decay occurred within 4 s of amass A=179 implant.

the PGAC to the DSSD. The data were then sorted inprompt (±100 ns) �-� and ↵��, and delayed ↵�↵ coin-cidence histograms, gated in various ways on the energyand time information from the DSSD.

The energy calibration of the DSSD was carried out us-ing known ↵ lines of 175Pt (5960(3) keV), 176Pt (5747(5)keV), 179Hg (6286 (4) keV) and 180Hg (6119(4) keV) thatwere produced in the present experiment. The energyand e�ciency calibrations of the Gammasphere and theGe CLOVER array at the FMA focal plane were per-formed using 152Eu and 182Ta radioactivity sources.

A. Decay of 179,179mTl

The energy spectrum of first-generation ↵-decay eventswith an additional requirement that the decay occurredwithin 4 s of a mass A=179 implant is shown in Fig. 1.The most intense peak at 6286 keV is assigned to the de-cay of 179Hg, while those at 6556 keV and 7194 keV areassociated with the decays of the ground and isomericstates of 179Tl, respectively. The measured energies arein good agreement with those reported in the previousstudies [17–20], as summarized in Table I. The peak at6431 keV is associated with the decay of the 175Au nu-clide, a daughter of 179Tl. Its presence in the spectrumis because some of the parent ↵ decays can escape theDSSD undetected, coupled with the shorter (hundred ofmilliseconds) lifetimes involved (see below in the text).The 179Tl and 179mTl half-lives were deduced from timespectra produced by gating on the corresponding first-generation ↵ decays, as shown in Fig. 2a and b, respec-tively. Our value for the ground state half-life is in agood agreement with that reported by Rowe et al. [18],but it is of better precision. However, it is much longer

1000 2000 3000 4000

10–1

100

101

Time (ms)

Cha

nnel

s

a)T1/2=476(19) ms

2 4 6 8 10 12 1410–1

100

101

102

103

Time (ms)

Cha

nnel

s

b)T1/2=1.36(4) ms

100 300 500 700 900 1100

10–1

100

101

Time (ms)

Cha

nnel

s

c)T1/2=188 (12) ms

100 300 500 700 900

10–1

100

101

Time (ms)

Cha

nnel

s

d)T1/2=124 (8) ms

6556α1(t) 7194α1(t)

6556α1-6431α2(t) 7194α1-6431α2(t)

FIG. 2: a) and b) time spectra produced by gating on firstgeneration E↵1=6556 keV (179Tl) and 7194 keV (179mTl)lines, respectively c) and d) time spectra produced by gatingon the second-generation E↵2=6431 keV line with additionalrequirements that it is correlated with the first-generationE↵1=6556 keV and 7194 keV decays, respectively.

when compared to the values reported in Refs. [20, 21].The measured half-life for the isomeric state is consistentwith the literature values, as presented in Table I.

Figure 3 shows Gammasphere �-ray spectra correlatedwith the 6556 keV and 7194 keV ↵ decays. As can beseen, some of the � rays in the two spectra are identical,thus implying that the isomer and the ground state areconnected via a �-ray branch. Unfortunately, it was notpossible to establish the connecting �-ray transition(s),presumably because of the long lifetime of the isomer. Asa consequence, it was not possible to directly determinethe excitation energy of the isomer. However, interpo-lation of the known excitation energies of 807 (18) keV(177Tl) [22], 895.9 (10) keV (181Tl) [23, 24] and 907.4(4) keV (183Tl) [25] for the I⇡=11/2� state associatedwith the spherical ⇡h11/2 configuration, allowed a valueof 860 (7) keV to be deduced for the 179mTl excitationenergy. As can be seen in Figure 3, the 227 keV and452 keV gamma rays are correlated only with E↵1=6556keV (179Tl), but not with E↵1=7194 keV (179mTl), andare therefore placed above the ground state, as shown inFig. 4. It is worth noting that � rays of similar energies(258 keV and 565 keV) were placed above the I⇡=1/2+

ground state in the neighboring isotope 181Tl [23, 24].The 231, 256, 340, and 455 keV � rays, and tentativelythe 189 keV one, precede the isomer, as evident fromFig. 3b. While the 231, 256 and 455 keV � rays were

1/2+  (g.s)   11/2-­‐  (iso)  

179Tl  –  g.s.  2

5000 6000 7000100

101

102

103

104

105

Eα1 (keV)

Cou

nts 71

946556

6431

6286A=179 gated

0 < Δtα1 < 4 s

FIG. 1: Energy spectrum of first-generation ↵-decay eventswith a requirement that the decay occurred within 4 s of amass A=179 implant.

the PGAC to the DSSD. The data were then sorted inprompt (±100 ns) �-� and ↵��, and delayed ↵�↵ coin-cidence histograms, gated in various ways on the energyand time information from the DSSD.

The energy calibration of the DSSD was carried out us-ing known ↵ lines of 175Pt (5960(3) keV), 176Pt (5747(5)keV), 179Hg (6286 (4) keV) and 180Hg (6119(4) keV) thatwere produced in the present experiment. The energyand e�ciency calibrations of the Gammasphere and theGe CLOVER array at the FMA focal plane were per-formed using 152Eu and 182Ta radioactivity sources.

A. Decay of 179,179mTl

The energy spectrum of first-generation ↵-decay eventswith an additional requirement that the decay occurredwithin 4 s of a mass A=179 implant is shown in Fig. 1.The most intense peak at 6286 keV is assigned to the de-cay of 179Hg, while those at 6556 keV and 7194 keV areassociated with the decays of the ground and isomericstates of 179Tl, respectively. The measured energies arein good agreement with those reported in the previousstudies [17–20], as summarized in Table I. The peak at6431 keV is associated with the decay of the 175Au nu-clide, a daughter of 179Tl. Its presence in the spectrumis because some of the parent ↵ decays can escape theDSSD undetected, coupled with the shorter (hundred ofmilliseconds) lifetimes involved (see below in the text).The 179Tl and 179mTl half-lives were deduced from timespectra produced by gating on the corresponding first-generation ↵ decays, as shown in Fig. 2a and b, respec-tively. Our value for the ground state half-life is in agood agreement with that reported by Rowe et al. [18],but it is of better precision. However, it is much longer

1000 2000 3000 4000

10–1

100

101

Time (ms)

Cha

nnel

s

a)T1/2=476(19) ms

2 4 6 8 10 12 1410–1

100

101

102

103

Time (ms)

Cha

nnel

s

b)T1/2=1.36(4) ms

100 300 500 700 900 1100

10–1

100

101

Time (ms)

Cha

nnel

s

c)T1/2=188 (12) ms

100 300 500 700 900

10–1

100

101

Time (ms)

Cha

nnel

s

d)T1/2=124 (8) ms

6556α1(t) 7194α1(t)

6556α1-6431α2(t) 7194α1-6431α2(t)

FIG. 2: a) and b) time spectra produced by gating on firstgeneration E↵1=6556 keV (179Tl) and 7194 keV (179mTl)lines, respectively c) and d) time spectra produced by gatingon the second-generation E↵2=6431 keV line with additionalrequirements that it is correlated with the first-generationE↵1=6556 keV and 7194 keV decays, respectively.

when compared to the values reported in Refs. [20, 21].The measured half-life for the isomeric state is consistentwith the literature values, as presented in Table I.

Figure 3 shows Gammasphere �-ray spectra correlatedwith the 6556 keV and 7194 keV ↵ decays. As can beseen, some of the � rays in the two spectra are identical,thus implying that the isomer and the ground state areconnected via a �-ray branch. Unfortunately, it was notpossible to establish the connecting �-ray transition(s),presumably because of the long lifetime of the isomer. Asa consequence, it was not possible to directly determinethe excitation energy of the isomer. However, interpo-lation of the known excitation energies of 807 (18) keV(177Tl) [22], 895.9 (10) keV (181Tl) [23, 24] and 907.4(4) keV (183Tl) [25] for the I⇡=11/2� state associatedwith the spherical ⇡h11/2 configuration, allowed a valueof 860 (7) keV to be deduced for the 179mTl excitationenergy. As can be seen in Figure 3, the 227 keV and452 keV gamma rays are correlated only with E↵1=6556keV (179Tl), but not with E↵1=7194 keV (179mTl), andare therefore placed above the ground state, as shown inFig. 4. It is worth noting that � rays of similar energies(258 keV and 565 keV) were placed above the I⇡=1/2+

ground state in the neighboring isotope 181Tl [23, 24].The 231, 256, 340, and 455 keV � rays, and tentativelythe 189 keV one, precede the isomer, as evident fromFig. 3b. While the 231, 256 and 455 keV � rays were

476  (19)  ms          present  

415  (55)  ms  –  LBNL  230  (40)  ms  –  ANL  (1998)  160  (+90-­‐40)  ms  –  GSI  (1993)  

179Tl  –  isomer  good  agreement  with  previous  measurements  

10  

175Au:  lifetimes 2

5000 6000 7000100

101

102

103

104

105

Eα1 (keV)

Cou

nts 71

946556

6431

6286A=179 gated

0 < Δtα1 < 4 s

FIG. 1: Energy spectrum of first-generation ↵-decay eventswith a requirement that the decay occurred within 4 s of amass A=179 implant.

the PGAC to the DSSD. The data were then sorted inprompt (±100 ns) �-� and ↵��, and delayed ↵�↵ coin-cidence histograms, gated in various ways on the energyand time information from the DSSD.

The energy calibration of the DSSD was carried out us-ing known ↵ lines of 175Pt (5960(3) keV), 176Pt (5747(5)keV), 179Hg (6286 (4) keV) and 180Hg (6119(4) keV) thatwere produced in the present experiment. The energyand e�ciency calibrations of the Gammasphere and theGe CLOVER array at the FMA focal plane were per-formed using 152Eu and 182Ta radioactivity sources.

A. Decay of 179,179mTl

The energy spectrum of first-generation ↵-decay eventswith an additional requirement that the decay occurredwithin 4 s of a mass A=179 implant is shown in Fig. 1.The most intense peak at 6286 keV is assigned to the de-cay of 179Hg, while those at 6556 keV and 7194 keV areassociated with the decays of the ground and isomericstates of 179Tl, respectively. The measured energies arein good agreement with those reported in the previousstudies [17–20], as summarized in Table I. The peak at6431 keV is associated with the decay of the 175Au nu-clide, a daughter of 179Tl. Its presence in the spectrumis because some of the parent ↵ decays can escape theDSSD undetected, coupled with the shorter (hundred ofmilliseconds) lifetimes involved (see below in the text).The 179Tl and 179mTl half-lives were deduced from timespectra produced by gating on the corresponding first-generation ↵ decays, as shown in Fig. 2a and b, respec-tively. Our value for the ground state half-life is in agood agreement with that reported by Rowe et al. [18],but it is of better precision. However, it is much longer

1000 2000 3000 4000

10–1

100

101

Time (ms)C

hann

els

a)T1/2=476(19) ms

2 4 6 8 10 12 1410–1

100

101

102

103

Time (ms)

Cha

nnel

s

b)T1/2=1.36(4) ms

100 300 500 700 900 1100

10–1

100

101

Time (ms)

Cha

nnel

s

c)T1/2=188 (12) ms

100 300 500 700 900

10–1

100

101

Time (ms)C

hann

els

d)T1/2=124 (8) ms

6556α1(t) 7194α1(t)

6556α1-6431α2(t) 7194α1-6431α2(t)

FIG. 2: a) and b) time spectra produced by gating on firstgeneration E↵1=6556 keV (179Tl) and 7194 keV (179mTl)lines, respectively c) and d) time spectra produced by gatingon the second-generation E↵2=6431 keV line with additionalrequirements that it is correlated with the first-generationE↵1=6556 keV and 7194 keV decays, respectively.

when compared to the values reported in Refs. [20, 21].The measured half-life for the isomeric state is consistentwith the literature values, as presented in Table I.

Figure 3 shows Gammasphere �-ray spectra correlatedwith the 6556 keV and 7194 keV ↵ decays. As can beseen, some of the � rays in the two spectra are identical,thus implying that the isomer and the ground state areconnected via a �-ray branch. Unfortunately, it was notpossible to establish the connecting �-ray transition(s),presumably because of the long lifetime of the isomer. Asa consequence, it was not possible to directly determinethe excitation energy of the isomer. However, interpo-lation of the known excitation energies of 807 (18) keV(177Tl) [22], 895.9 (10) keV (181Tl) [23, 24] and 907.4(4) keV (183Tl) [25] for the I⇡=11/2� state associatedwith the spherical ⇡h11/2 configuration, allowed a valueof 860 (7) keV to be deduced for the 179mTl excitationenergy. As can be seen in Figure 3, the 227 keV and452 keV gamma rays are correlated only with E↵1=6556keV (179Tl), but not with E↵1=7194 keV (179mTl), andare therefore placed above the ground state, as shown inFig. 4. It is worth noting that � rays of similar energies(258 keV and 565 keV) were placed above the I⇡=1/2+

ground state in the neighboring isotope 181Tl [23, 24].The 231, 256, 340, and 455 keV � rays, and tentativelythe 189 keV one, precede the isomer, as evident fromFig. 3b. While the 231, 256 and 455 keV � rays were

1/2+  (g.s)   11/2-­‐  (iso)  similar,  but  not  iden2cal!  

188  (12)  ms  –  124  (8)  ms  

158  (3)  ms  using  6432α(t)  

F.G.  Kondev  et    al.,  PLB  512  (2001)  

3

0

4

8

12

(189

)

256

340

227

\ /

231

\/45

2 455

a)

100 200 300 400 5000

4

8

12

Energy (keV)

Cou

nts

(189

) 256

340

231

455

b)

Tl X

-rays

FIG. 3: a) and b) prompt �-ray spectra, correlated with the6556 keV (179Tl) and 7194 keV (179mTl) ↵ lines, respectively.

found to be in a prompt coincidence, the 340 keV gammaray was in prompt coincidence only with the latter two,but not with the 231 keV � ray.

B. Decay of 175,175mAu

In our previous studies [26], only the decay of 175mAuwas reported with E↵=6.43 MeV and T1/2=143 (8)ms. Our findings were confirmed in the recent workof Andreyev et al. [17], where correlations between theE↵1=7207 (5) keV (179mTl) and E↵1=6432 (5) keV(175mAu) ↵ lines were observed, and T1/2=138 (5) mswas reported for the later, but they did not provide in-formation of the ground state. Rowe et al. [18] assigneda E↵=6438 keV to 175Au, as they reported that it wascorrelated with both the 179Tl and 179mTl ↵ decays. Asecond ↵ line with E↵=6412 keV was found to be cor-related with the 5717 (10) keV one, associated with thedecay of 171Ir ground state [18]. Page et al. [19] assigned6438 (9) keV ↵ line to decay of 175Au.

Present work resolved the ambiguities that existed forthe decay of 175,175mAu. Figure 5a and 5b show second-generation alpha spectra produced by gating on first-

generation E↵1=6556 keV (179Tl) and 7194 keV (179mTl).The two spectra look nearly identical, with the 6431 keV↵ line associated with 175Au and the 5965 keV one withthe decay of 175Pt. Importantly, third-generation spec-tra, produced by double-gating on 6556↵1-6431↵2 (Fig-ure 4c) and 7194↵1-6431↵2 (Figure 4d) clearly indicatethat di↵erent third-generation ↵ lines with E↵=5728 keVand 5958 keV are correlated with the 6431 keV one. Thisimplies that both the ground state and the isomer in175Au are depopulated by ↵ decays with nearly-identicalenergies. The half-lives of 188 (12) ms and 124 (8) mswere obtained for the ground state and the isomer in175Au, as shown in Figure 2c and 2d, respectively, whichare similar, but not identical. Clearly, our previously re-ported value [26] contains contributions from both theisomer and the ground state. If one takes the excitationenergy of the isomer in 179Tl as 860 (7) keV and the mea-sured here ↵ energies, then the excitation energy of 207(14) keV can be obtained for the isomer in 175Au.The presence of 5965 keV ↵ line in the spectra shown in

Figure 5a and 5b, suggests that both 175Au and 175mAuhave EC-�+ branches. Given the known ↵-decay branch-ing ratio of b↵= 64 (5)% for 175Pt [41], one can deduceb↵= 89(3)% and 78 (4)% for 175Au and 175mAu, respec-tively. The deduced in the present work b↵ value for175mAu is somewhat lower compared to that of 90 (3)%reported by Andreyev et al. [17].Three ↵ lines were known in the decay of 175Pt and

the present work confirm that. A half-life of 2.30(1) swas obtained for 175Pt, which is in good agreement withthe previous studies, as shown in Table I. The stronger(favorite) decay feeds the 7/2� level of the 5/2� bandin the daughter 171Os nuclide, while the week 5841(8)keV feeds the 9/2� band member. Gamma-ray spectradetected in the CLOVER array in coincidence with the5961 and 5841 keV ↵ lines are shown in Figure. 6. Themeasured �-ray energies are in agreement with those re-ported in [28, 39]. However, the energies of 133.5 keVand 209.8 keV gamma rays are systematically higher thanthose of 130.78 and 207.64 keV reported in the in-beamstudies [42].

C. Decay of 171,171mIr

While a somewhat detailed data are known for the de-cay of 171mIr, only little is known for the decay of theground state. The present work clearly establishes thatthe 5728 keV line is associated with the 171Ir, as evi-dent of the correlations with 179Tl!175Au!171Ir, seenin Fig. 2. The measured half-life is in agreement with thevalue reported by Rowe at el.[18], but it is more precise.The observed 5958 keV ↵ line for the isomer is some-what larger compared to that reported by Andreyev etal. [17], but it is in agreement with that observed by Pageet al. [19]. We do confirm that this decay feeds the ex-cited state that decays via a 92 keV �-ray transition tothe 9/2� ground state. It is therefore possible that the

11  

179Tl:  in-­‐‑beam  data

ü  connec2on  between  the  11/2-­‐  isomer  and  the  1/2+  g.s.  

similar  to  181Tl:  M.P.  Carpenter  et  al.    

7182α

6556α

6556α

7182α

4

1/2+

11/2-

(3/2+)

(5/2+)

1/2+

1/2+

1/2+

9/2-

11/2-

11/2-

11/2-

860(7)

0

0

0

0

207(14)

207(17)

9289(19)

227a

452a 227

679

92a

6556_

5728_

6431_

7194_

5958_

6431_

179Tl

175Au

171Ir

167Re

476 ms

1.36 ms

188 ms124 ms

3.1 s1.51 s

3.4 s5.9 s

%b_=100

%b_=50

%b_=78

%b_=89

%b_=54%b

_~100

FIG. 4: Schematic decay chain originating from 179Tl and terminating in 163Ta.

5600 6000 6400

5

10

15

20

25

Cou

nts

Eα3 (keV)

0 < Δt(α2-α3) < 40 s6556α1-6431α2 gated(c)

5728

5600 6000 6400

101

102

Eα2 (keV)

Cou

nts

(a) 6556α1 gated0 < Δt(α1-α2) < 2 s

5965

6431

5600 6000 6400

101

102

(b) 7194α1 gated0 < Δt(α1-α2) < 2 s

5965

6431

Cou

nts

5600 6000 64000

10

20

30

40

Cou

nts

Eα3 (keV)

(d) 7194α1-6431α2 gated0 < Δt(α2-α3) < 20 s59

58

Eα2 (keV)

FIG. 5: a) and b) ↵ spectra produced by gating on first-generation E↵1=6556 keV (179Tl) and 7194 keV (179mTl) lines,respectively c) and d) ↵ spectra produced by gating on the second-generation E↵2=6431 keV line with additional requirementsthat it is correlated with the first-generation E↵1=6556 keV and 7194 keV decays, respectively.

5958 keV line is a sum of the real ↵ and the conversionelectrons. If one consider the binding energy of 20.3 keV,then E↵= 5938 (8) keV would be expected. Using the

deduced excitation energy of 207 (14) keV for 175mAuand assuming the same energy of 6431 (8) keV, one candeduce the excitation energy of the isomer in 171mIr as

Theoryi

Exp

Theoryi

Exp

i TBRT

TTHF

2/1

2/1

2/1

2/1 /)(==

α TheoryT 2/1 M.A. Preston, Phys. Rev. 71 (1947) 865

HF  <  4  favorite  (ΔL=0)decay      

1.12  (6)   0.50  (3)  

2.16  (17)   1.63  (19)  

2.2  (4)  0.36  (6)  %bα~15%  

1/2+   11/2-­‐  

Odd-­‐‑odd  Tl  nuclei? q 181-­‐198Tl  (N=100-­‐117)  isotopes  ü  spherical  ground  state  –  1/2+  (s1/2)  ü  oblate-­‐deformed  isomer  –  9/2-­‐  (h9/2)    q 179-­‐199Pb  (Z=82)    ü  spherical  ground  state  –  3/2-­‐  (p3/2)  ü  spherical  isomer  –  13/2+  (i13/2)  

 q odd-­‐odd  Tl:    ü  low  (2-­‐)  and  high-­‐spin  (7+)  isomers  

but  …  changes  in  structure  of    neutron-­‐deficient  Pb  below  181Pb    

ü  Jπ=9/2-­‐  instead  of  3/2-­‐  ,  associated    with  deforma2on  related  effects  ü  do  such  changes  affect  Tl  nuclides?    

(3-­‐)  

(3-­‐)  

(9+)  

(8+)   212   175  

6.22  6.28  

6.12  6.08  

176Au  

172Ir  

J.T.M.  Goon,  PhD  thesis,  UT  

T1/2=1.05  s  T1/2=1.4  s  

84Sr  +  94Mo@178Hg  (pn)176Au  Gammasphere  &  FMA  

A=176  

gammasphere  

15  

180Tl: α decay

176Pt  176Au  ε+β+

180Tl    (1n)  

180Hg    (1p)  

%α =  80  (8)  %ε+β+=20  (8)  

α

172Ir  

(3-­‐)  

(3-­‐)  

(9+)  

(8+)   212   175  

6.29  6.28  MeV  

6.12  6.08  

176Au  

αε+β+

5.76  MeV  α

176Pt  

16  

180Tl: α-γ coincidences

ü  decay  of  a  single  state  in  180Tl  16  

Au  X-­‐rays  known  in  176Au  

180Tl:  Iπ=4-­‐  and  5-­‐:  π1/2+  (s1/2)  x  ν9/2-­‐  (h9/2)  -­‐  favored  α-­‐decay  176Au:  Iπ=3-­‐  and  4-­‐:  π1/2+  (s1/2)  x  ν7/2-­‐  (ff/2)    

(4-­‐)  

180Tl:  in-­‐‑beam  gamma  rays

Conclusions  &  Outlook

q symmetric  HI  fusion  reac2ons  at  energies  near  the  Coulomb  barrier  in  conjunc2on  with  the  RDT  technique  are  powerful  tool  to  study  proton-­‐rich  nuclei  at  the  edge  of  stability    

q 179Tl:  long-­‐lived  1/2+  g.s.  and  a  shorter-­‐lived  11/2-­‐  isomer,  both  associated  with  spherical  shape  –  decay  correla2ons  were  essen2al;  established  the  “missing”  g.s.  of  175Au  

q 180Tl:  a  single-­‐decaying  state;  Iπ=(4,5)-­‐:  π1/2+  (s1/2)  x  ν9/2-­‐(h9/2)  

q  future:  life2me  measurements  for  the  prolate-­‐deformed  bands  known  in  Au/Tl  isotopes  to  ascertain  deforma2on  and  shape  –  using  DSAM  &  direct  2ming  technique  using  LaBr3  scin2lla2on  detectors;  digital  Gammasphere  and  DSSD  

Collaborators  

Supported by the Office of Nuclear Physics, U.S. DOE

M.P.  Carpenter,  S.  Zhu,  R.V.F.  Janssens,  I.  Ahmad,  B.B.  Back,  P.F.  Bertone,  J.  Chen,  C.J.  Chiara,  C.A.  Copos,  J.P.  Greene,  G.  Henning,  C.R.  Hoffman,  B.P.  Kay,  T.L.  Khoo,  T.  Lauritsen,  E.A.  McCutchan,  C.  Nair,    A.M.  Rogers,  D.  Seweryniak

Argonne  National  Laboratory

           D.J.  Hartley                          US  Naval  Academy

Thank  you!