REINA() DE TRABALHO SOBRE FiSICA NUCLEAR NO BRASIL

20 Estrutura Nuclear - XX RTFNB
The isotopes Z= 57, 131) . 132' 134' 136 ' 1361A [1,2,3,4], were
studied by this group during the last years. At low
spins these nuclei are 7-soft with moderate quadrupole
deformation (32 0.2).
The 137La nucleus has been produced in the 430Te
11B fusion reaction at 49 MeV beam energy. The beam
was provided by the Pelletron Tandem Accelerator of
the University of Sao Paulo. The experiment was performed
using the GBR [5] array consisting of 4 FIPGe
detectors and a multiplicity filter of 7 Na! scintillators
(6 of 3"x3" and 1 of 4"x4"). Two detectors are Ortec
GMX of about 20% efficiency with BGO Compton suppressors
while the other two are Canberra REGe with
60% efficiency. Events were collected when at least 2
Ge detectors and 1 scintillator detector fired in coincidence.
Approximately 12x10 7 7-y coincidence events
were recorded. The data have been sorted off-line into
a symmetrized matrix and is being analysed. The preliminary
level scheme for 137La obtained in this work
was extended to much high energies as compared to the
first scheme proposed by Kortelahti [6]. Several new
structures were observed, one of them populating the
already known 360ns (IT` = 19/2 — ). Careful analysis
of the data is being performed in order to clarify the
character of these structures.
[1] M.A. Rizzutto, Thesis, Laboratorio Pelletron, Departamento
de Fisica Nuclear, Universidade de Sao Paulo,
Brasil 1989, unpublished.
[2],I.R.B. Oliveira et al., Phys. Rev. C39, 2250 (1989).
[3]J.R.B. Oliveira et al., Phys. Rev. C45, 2740 (1992).
[4]M.A. Rizzutto at al., X VII Reunido de ?baba/ho de
Fisica Nuclear no Brasil - 1994.
[5]Annual Report - University of Sao Paulo - Nuclear
Physics Department - 1996, pg. 63.
[6]M. Koertelabti et al., Nucl. Phys. A376, 1 (1982).
SPECTROSCOPY OF HIGHLY NEUTRON
DEFICIENT NUCLEI AROUND A 140
M. N. RAO, M. A. RIZZUTTO, N. H. MEDINA, J.
R. B. OLIVEIRA, R. V. RIBAS, E. W. CYBULSKA,
J. C. ACQUADRO, W. A. SEALE
Instituto de Fisica, Universidade de Sdo Paulo, Sao Paulo,
Brazil
F. R. ESPINOZA-QUI5TONES
Departamento de Fisica - CCE, Universidade Estadual de
Londrina, Londrina, PR, Brazil
D. BAZZACCO, C. A. UR, S. LUNARDI, C.
ROSSI-ALVAREZ, F. BRANDOLINI, C. PETRACHE, ZS.
PoDOLVAX
Dipartimento de Fisica and INFN, Sezioni di Padova,
Padova, Italy
C. DE ANGELIS, D. R. NAPOLI, P. SPOLAORE, A.
CADEA, D. DE ACCIYA, M. DE Pcn,i, E. FARNEA, D.
FOLTESCU
INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy
M. IONESCU-BUJOR, A. IORDACHESCU
Institute of Physics and Nuclear Engineering, Bucharest,
Romania and Dipartirnento de Fisica and INFN, Sezioni
di Padova, Padova, Italy
L. SAJO Bonus
Instituto de Fisica, Universidad Simon Bolivar, Caracas,
Venezuela
A. CHATTERJEE, A. SAXENA
Bhabha Atomic Research Center, Bombay, India
Data on the structure of nuclei in the neighbourhood of
the proton drip line are scarce since these nuclei, situated
far from the stability valley, are hard to produce
and study. We have used the
34Fe k 92Mo reaction at 240-MeV incident beam
energy, in order to investigate neutron deficient nuclei
in the A rs 140 mass region.
The incident beam was obtained with the XTU tandem
accelerator of the Legnaro National Laboratory, Legnaro,
Italy. The multi-detector array GASP, consisting
of 40 high-efficiency Compton-suppressed HpGe detectors
and the 80-element BGO multiplicity filter, was
used for obtaining gamma-ray double and triple coincidence
spectra. The 40-telescope Si ball (ISIS) per
information on the type and multiplicity of' the
charged particles emitted, while the recoil mass spectrograph
(CAMEL) allowed mass identification.
The following 3 and 4 particle reaction channels were
strongly populated: 1.43Tb , 140,142Gd , 143Dy. Preliminary
results on the high-spin states seen in 143Tb in the
present work are described elsewhere in this report. Several
gamma transitions have been assigned to belong
to the 2pu channel 143Dy. Previous to this work no
information was available on the spectroscopy of this
nucleus. The 3pn channel leading to 142Tb has a large
predicted cross section. No data on high-spin states in
this odd-odd nucleus is known in literature. Among the
other nuclei predicted to be populated at this incident
energy, by statistical model codes (CASCADE, PACE),
with weaker cross sections, it has been possible to assign
transitions in the odd-odd nucleus 14°Tb, from the
apn channel, also for the first time.
Of the 2-particle outgoing channels, transitions in the
2p ( 144Dy) and the ap ( 441Tb) channels are strong. The
2e channel is much weaker and efforts are underway to
detect the en channel leading to 144 Dy, with a predicted
cross section of around 1 % of the total fusion cross
section. The data analysis is in progress.
HIGH-SPIN STATES IN 143Tb
F. R. EselNoZA-QuigoNES
Dcpartamento de Fisica - CCE, Universidade Estadual de
Londrina, Londrina, PR, Brazil
M. A. FttzztreTo, M. N. RAO, N. H. MEDINA, E.
W. CYBULSKA, J. F. 13. OLIVEIRA, R. V. MBAS
Instituto de Fisica - USP, Dpto. Fisica Nuclear
D. BAZZACCO, C. A. UR, S. LUNARDI, C.
ROSSI-ALVAREZ, F. BRANDOLINI, C. PETRACHE, ZS.