paul e. garrett university of guelph
TRANSCRIPT
Paul E. Garrett University of Guelph
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• Spins of the neutrons generally couple to S = s1+s2 = 0, most states observed are natural parity (J=L)
A target
A-2 final
Proton
Triton
• Pair transfer probes pairing components of wave functions
θ
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• Shape of angular distribution in two-nucleon transfer rather insensitive to individual j involved in pair transfer
• Ratio of excited 0+ to gs cross sections normally expected to be on order of few% for 2 qp excitation
• 0+ state cross section
• Relative population on order of 10% indicative of enhanced transition – a collective pairing transition – at least in conventional wisdom
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!∝(∑↑▒('↓) +↓)↑" ) )↑"
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0+ 0+ 0+
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0+ 0+ 0+
0+
0+
0+
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Adapted from W. D. Kulp et al. PRC 71, 041303(R) (2005)
152Sm 154Gd
Large asymmetry between (t,p) and (p,t) strength in N=90 region
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? 160Er 158Dy
156Gd
Consistent strong population of 02
+ state across N=92 isotones ?
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• 22-24 MeV proton beams up to 1 µA current
• Typical resolution ~ 8 keV FWHM
• Coverage up to ~ 2.4
– 3.2 MeV excitation energy
• Targets of 162Er (natural abundance 0.14%) , 164Er (1.6%) produced by running separated isotope through Florida State separator in 1960’s • Resulting enrichment
>99%
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• Q3D magnetic spectrograph momentum analyzes reaction ejectiles
tritons
protons � Focal plane detector
allows for particle identification, and gives position along focal plane
Energy (keV)
0+
2+
4+
6+
2+ 2+
0+ 2+
18.99(22) %
1.03(4) %
3+
0+
4+
6+, 6+
6+
4+ 6+ 2+
4+ 4+
4+
0+
0+ 0+
4+
2+
2+
6+
2+
4+ 0+
0+
0.76 (6) %
1.88 (8) %
0.10 (3) %
0.98 (5) %
2.09 (9) %
Cou
nts
E= 0 MeV (0+1) E=1929 keV (0+
6)
• Ratio of Exp/DWBA cross sections will provide a Q-value correction for kinematics
160Er
158Dy
156Gd
Confirmed strong population of 02
+ state across N=92 isotones
Consistent properties of 02+ states points to common structure
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160Er
162Er 164Er
166Er 168Er
160Er
162Er
164Er
166Er
168Er There is a shift in the
strength away from the 02
+ state beyond 164Er.
Bucurescu et al. PRC 73, 064309 (2006)
Burke and Garrett, NPA 550, 21 (1992)
This Work
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154Gd ground state vacuum and excitations
154Gd second vacuum and excitations lowered by 681 keV
152Sm ground state vacuum and excitations
152Sm second vacuum and excitations lowered by 685 keV
J.F. Sharpey-Schafer. Eur. Phys. J. A (2011) 47: 5 26/09/2016 16
• The steeply up-sloping ν11/2[505] orbital is blocked in 155Gd
J.F. Sharpey-Schafer. Eur. Phys. J. A (2011) 47: 6 26/09/2016 17
ν11/2[505] believed to be a dominant configuration in the 02
+ state at N=90
Indication that the 0+ strength tracks with the Fermi surface, and specifically the 11/2[505] orbital
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• The 02+ state in N=92, 94, 96 Er possesses a high degree of
coherence in its wave function evinced by the collective (p,t) transitions
• Appears to be very robust excitation across the N=92 isotones as well
• As Fermi level changes, the collective (p,t) transitions track with it, and become increasingly fragmented but apparently stronger • Indications that 11/2[505] playing a very important role
• Need spectroscopic data on excited 0+ bands to fully characterize excitation
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S. TRIAMBAK
T. FAESTERMANN R. HERTENBERGER H.-F. WIRTH
G.C. BALL K.G. LEACH
C. BURBADGE V. BILDSTEIN A. DIAZ VARELA M. R. DUNLOP R. DUNLOP D.S. JAMIESON D. KISLIUK A. FINLAY J. LORANGER A. D. MACLEAN A. J. RADICH E. T. RAND C.E. SVENSSON
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• Dominating GS→GStransition strengths until 152Sm, 154Gd
• For N<90 population to 02
+ and 03
+ strong
• For N>90 population only to 02
+ strong J.L. Wood et al. Phys. Rep. 215, Nos. 3 & 4 (1992)
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