This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Berg, G.P.A.

Grabmayr, P.

Lisantti, J.

Miller, D.W.

Mondry, A.

Nann, H.

Singh, P.P.

Stephenson, E.J.

Wagner, G.J.

Woldt, P.

English

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In this case, the Ay gives information mainly on the distorting potentials, and seems 
no more sensitive to the l-transfer than the cross section. However, a full finite range 
calculation (with a spin dependent interaction) will allow A S  = 1 transitions and hence 
the excitation of unnatural parity states. 
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2. G.E. Brown, et al., Phys. Rev. Lett. 60, 2723 (1969); also G.E. Brown and M. Rho, 
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4. D.C. Zheng and L. Zamick, in The Effects of Spin-orbit and Tensor Interactions in 
Nuclei, Rutgers University preprint, October 1990. 
SEARCH FOR 3s1/2 HOLE-STRENGTH FRAGMENTS VIA THE 
208Pb(d,3He)207Tl REACTION 
P. Grabmayr, A. Mondry, G.J. Wagner, and P. Woldt 
Physikalis ches Lisbibut de Universitat Tubingen, Germany 
G.P.A. Berg, J.  Lisantti, D.W. Miller, H. Nann, P.P. Singh, and E.J. Stephenson 
Indiana University Cyclotron Facility, Bloomington, Indiana 47408 
Studies of fractional occupation numbers of shell-model orbitals in doubly-magic nuclei 
with the proton removal reactions ( d , 3 ~ e )  and (e,elp) yield insights into the limitations of 
the mean-field description of nuclei. Unfortunately, occupation numbers are not directly 
measurable, but can be derived in a model-dependent way through sum rules from absolute 
spectroscopic factors. 
For the doubly-closed shell nucleus 208Pb, recent mean field calculations by Mahaux 
et al.' predict an occupancy of 85% at the Fermi surface, whereas calculations of Pand- 
haripande et al. ,2 based on nuclear matter results, yield only 64%. 
It has been shown that occupancies with less model dependencies can be derived via 
the CERES approach3 which combines the results of the charge density measurements4 
with relative spectroscopic factors. Here the uncertainties of DWBA and DWIA calcula- 
tions are greatly reduced. Thus, occupation numbers derived via the CERES approach 
depend mostly on the interpretation of the charge density difference in terms of an inde- 
pendent particle model. 
Previous (d,3 He) experiments on 208 Pb have focused in general only on the five domi- 
nant single- hole st ate^.^-' Consequently, all recent analyses of proton removal experiments 
have assumed no l=0 transition to be present except for the transition to the ground state 
of 2 0 7 ~ l .  However, by combining the results of old (t ,a)'' and (t ,p)" investigations, two 
additional l=0 fragments around E, N 4.5 MeV have been reported,12 but without speci- 
fication of the spectroscopic strengths. As the absence of significant l=0 strength besides 
the 207Tl ground state transition is important for the CERES approach, we undertook the 
present search for weak l=0 transitions in the 2 0 8 ~ b ( d , 3 ~ e ) 2 0 7 ~ 1  reaction. 
Vector polarized deuterons (Py N 0.55) were accelerated by the Indiana University 
Cyclotron Facility (IUCF) to 80 MeV and focused onto a 1.38 mg/cm2 thick 208Pb foil, 
enriched to 99%. The reaction products were analyzed by the K600 magnetic spectrograph 
which was set up (together with the beamline) in a dispersion-matching mode. The beam 
itself was stopped in a Faraday cup within the scattering chamber as the spectrometer was 
set to scattering angles in the range of 4' to 28'. Particle identification was performed 
by a combination of the time-of-flight of the ejectile and its pulse height deposited in a 
scintillation detector. Kinematical corrections and determination of the actual scattering 
angle were performed off-line; a final overall resolution of 55 keV, predominantly due to 
the target thickness, was obtained. 
Angular distributions for cross sections and analyzing powers were obtained for final 
states up to about 5 MeV of excitation. Selected angular distributions are presented 
in Fig. 1. The full lines represent exact finite-range DWBA predictions performed with 
2 0 8 ~ b ( d ~ ~ e ) 2 0 7 ~ ~  
E, = 80 MeV 
- 
- 
MeV ': 
h/g : 
- 
* 
zo8~b(d,3~e)207~l  
Ed = 80 MeV 
L 
0.50 - 
: Ex / MeV 
0.130 - + 4.44 h/g 
Figure 1. Angular distribution of cross sections (left panel) and analyzing powers (right 
panel) of the 208~b(d,3He)207T1 reaction. The curves represent exact finite range DWBA 
calculations for the pickup from the orbitals indicated. 
the code DWUCK5 using the parameters of Radhakrishna et a1.l3 Detailed spectroscopic 
information for higher lying hole states of 'O7TI could be extracted. In particular, several 
spin and parity assignments could be made on the basis of characteristic distributions. 
With regard to the fragmentation of the 3slIz hole strength, the present analysis shows 
that the two known 1/2+ states indeed carry no !=0 strength exceeding CC2S = 0.04, 
i.e. 2.4% of that of the ground state transition. The upper limit of total possible 3slI2 
strength in the valence region (E, 5 5 MeV) is 5% of that of the ground state transition. 
This value is about the same as the result of (0 5)% provided by the analysis of the 
quasi-free (e,elp) reaction. l4 
1. C. Mahaux and R. Sartor, in Advances in Nuclear Physics, Vol. 20, ed. J.W. Negele 
and E. Vogt (Plenum Press, New York, 1991) p. 1. 
2. V.R. Pandharipande, C.N. Papanicolas, and J. Wambach, Phys. Rev. Lett. 53, 1133 
(1984). 
3. G.J. Wagner, in Proc. Int. School of Nuclear Physics, Erice, July 1989, ed. A. Faessler, 
Prog. Part. Nucl. Phys. 24, 17 (1990). 
4. J.M. Cavedon et al., Phys. Rev. Lett. 49, 978 (1982). 
5. S. Hinds et al, Nucl. Phys. 83, 17 (1966). 
6. W.C. Parkinson et al., Phys. Rev. 178, 1976 (1969). 
7. D. Royer et al., Nucl. Phys. A158, 516 (1970). 
8. P.W. Woods et al., Phys. Lett. B116, 520 (1982). 
9. E.R. Flynn et al., Nucl. Phys. A279, 394 (1977). 
10. P.D. Barnes et al., Phys. Rev. C 1, 228 (1970). 
11. 0. Hansen et al., Nucl. Phys. A127, 71 (1969). 
12. M.R. Schmorak, Nucl. Data Sheets 43, 383 (1984). 
13. M.C. Radhakrishna et al., Phys. Rev. C37, 66 (1988). 
14. P.K.A. de Witt Huberts, J. Phys. G: Nucl. Part. Phys. 16, 507 (1990). 


Search for 3S(1/2) Hole-Strength Fragments via the 208-Pb(d,3-He)207-Tl Reaction

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Search for 3S(1/2) Hole-Strength Fragments via the 208-Pb(d,3-He)207-Tl Reaction

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