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Strong L = 0 and 2 transitions in (p, t) reactions in even-mass Nd isotopes
Volume
29B, number
10
PEISICS
STRONG
LETTERS
18 August 1969
L = 0 AND IN
2 TRANSITIONS IN (p, EVEN-MASS Nd ISOTOPES
t)
REACTIONS
K. YAGI, Y. AOKI, J. KAWA and K. SAT0 Department
of Physics.
Faculty
of Science. Received
Osaka lJnir>ersity.
Osaka.
Japan
4 Julv 1969
The pairing vibrational states near N = 82 were investigated Nd isotopes of A = 142 - 150. Strong L. = 0 and 2 transitions observed for the 144Nd@. t) reaction.
The pairing vibrational states predicted by A. Bohr [l] were investigated in the mass region near N = 82. No systematic studies by means of two-nucleon transfer reactions have been made near the closed shell N = 82, whereas some experimental evidence concerning pairing vibrational transitions near N = 126 and 28 was found [ 11. Differential cross sections of the (p, t) reactions on the even-mass Nd isotopes of A = 142, 144, 146 and 150 were measured by the use of a 51.7 MeV proton beam from the INS Tokyo synchrocyclotron. Emitted particles were analyzed with a broad-range magnetic spectrometer and detected with 200 proportional counters [2]. The experimental setup was similar to that described in previous papers [3] except for an increase of the intensity of the debunched beam up to about 60 nA. The Nd targets were isotopically enriched (98%) films of Nd203 (about 4.0 mg/cm2) on Mylar backings. The uncertainty in the excitation energies is estimated to be 20 keV.
Toyonaka.
by means of (a. t) reactions on the even-mass to the expected pairing vibrational states were
Figs. l(a) - (c) show the triton spectra in the 142-146Nd(p, t) reactions. For 144Nd(p, t), no strongly excited states were found for E’, % 2.9 MeV; the known 2+(1.57 MeV), 3-(2.09 MeV) and Of(2.21 MeV) states [4] were excited very weakly as shown in fig. l(b). Strong L = 0 and 2 transi tions were, however, observed to states at Ex = 2.91 and 3.43 MeV, respectively. The L =0 transition and the L = 0 142Nd(p, t) 140Nd(g. s) transition have nearly the same Q-value (fig. 3) and the same cross section (fig. 2). Therefore, the 2.91 MeV (O+) state in 142Nd is considered to be approximately the pairing vibrational (1,l) state [l], and the 3.43 MeV (2+) state to be approximately the pairing-quadrupole state. Thick solid lines in fig. 3 indicate the strongly excited states in the (p, t) reactions. In the 146Nd(p, t) reaction, the L = 0 transition to the 3.17 MeV state had nearly the expected Qvalue (fig. 3), but its cross section was much smaller than that of the L= 0 142Nd(p,t)142Nd(g.s.)
-Ex(MeV) ‘44Ndp,t)
-&x(MeV) ‘46Nd(p,t)
r+
COUNTER NUMBER Fig. 1. Triton
spectra
( 0 = 5.5’)
from the @. t) reactions
on Nd of A = 142. 144 and 146.
647
Volume
29B. number
PHISICS
10
18 August 1969
LETTERS
Q=-9.19 140
aye y 142
144
146
Fig. 3. Level schemes obtained from the 142,1~ ldfiN(p,t) reactions. The thick solid lines indicate the strongly excited states.
0
20 _ 40 @CM
DEG
-&+w& @CM
The authors would like to express their thanks to Drs. M. Kondo, I. Miura, A. Shimizu and M. Inoue for their help with the experiment, and to the staff members of the INS cyclotron for their hospitality and cooperation.
Fig. 2. Angular distributions of L = 0 and 2 transitions in the 142.144,146 Nd(p, t) reactions. The smooth curves are drawn to guide the eye. Full circles indicate transitions to the ground-state band. open circles correspond to the pairing vibrational band.
On the other hand, the L = 2 transition to the 3.48 MeV state in 144Nd was strong enough to be compared with the L = 2 transition to the 0.78 MeV state in 140Nd (fig. 2). In the (p, t) reactions on 148Nd and l5oNd, no strong L. = 0 or 2 transitions were observed with Q-values of about -9 MeV. Therefore, the pairing vibrational strength seems to be fragmented such that the simple zero-order picture breaks down for N = 84-88. transition.
*****
648
References A. Bohr.
Proc.
Intern. Symp. Nuclear
structure.
Dubna. 1968; 0. Nathan. Proc. Intern. Symp. Nuclear structure. 1968. K. Yagi et al., Nucl. Instr. Methods 52 (1967) 29; K. Matsuda et al., Nucl. In&r. Methods 53 (1967) 82. K. Yagi et al., Nucl. Phys. A 111 (1968) 129; A 121 (1968) 161; J. Phys. Sot. Japan 24 (1968) 1167. C. N;. Lederer et al. i editors. Table of Isotopes, 6th ed., (John Wiley and Sons, Inc.. 1967) p. 291.
29B, number
10
PEISICS
STRONG
LETTERS
18 August 1969
L = 0 AND IN
2 TRANSITIONS IN (p, EVEN-MASS Nd ISOTOPES
t)
REACTIONS
K. YAGI, Y. AOKI, J. KAWA and K. SAT0 Department
of Physics.
Faculty
of Science. Received
Osaka lJnir>ersity.
Osaka.
Japan
4 Julv 1969
The pairing vibrational states near N = 82 were investigated Nd isotopes of A = 142 - 150. Strong L. = 0 and 2 transitions observed for the 144Nd@. t) reaction.
The pairing vibrational states predicted by A. Bohr [l] were investigated in the mass region near N = 82. No systematic studies by means of two-nucleon transfer reactions have been made near the closed shell N = 82, whereas some experimental evidence concerning pairing vibrational transitions near N = 126 and 28 was found [ 11. Differential cross sections of the (p, t) reactions on the even-mass Nd isotopes of A = 142, 144, 146 and 150 were measured by the use of a 51.7 MeV proton beam from the INS Tokyo synchrocyclotron. Emitted particles were analyzed with a broad-range magnetic spectrometer and detected with 200 proportional counters [2]. The experimental setup was similar to that described in previous papers [3] except for an increase of the intensity of the debunched beam up to about 60 nA. The Nd targets were isotopically enriched (98%) films of Nd203 (about 4.0 mg/cm2) on Mylar backings. The uncertainty in the excitation energies is estimated to be 20 keV.
Toyonaka.
by means of (a. t) reactions on the even-mass to the expected pairing vibrational states were
Figs. l(a) - (c) show the triton spectra in the 142-146Nd(p, t) reactions. For 144Nd(p, t), no strongly excited states were found for E’, % 2.9 MeV; the known 2+(1.57 MeV), 3-(2.09 MeV) and Of(2.21 MeV) states [4] were excited very weakly as shown in fig. l(b). Strong L = 0 and 2 transi tions were, however, observed to states at Ex = 2.91 and 3.43 MeV, respectively. The L =0 transition and the L = 0 142Nd(p, t) 140Nd(g. s) transition have nearly the same Q-value (fig. 3) and the same cross section (fig. 2). Therefore, the 2.91 MeV (O+) state in 142Nd is considered to be approximately the pairing vibrational (1,l) state [l], and the 3.43 MeV (2+) state to be approximately the pairing-quadrupole state. Thick solid lines in fig. 3 indicate the strongly excited states in the (p, t) reactions. In the 146Nd(p, t) reaction, the L = 0 transition to the 3.17 MeV state had nearly the expected Qvalue (fig. 3), but its cross section was much smaller than that of the L= 0 142Nd(p,t)142Nd(g.s.)
-Ex(MeV) ‘44Ndp,t)
-&x(MeV) ‘46Nd(p,t)
r+
COUNTER NUMBER Fig. 1. Triton
spectra
( 0 = 5.5’)
from the @. t) reactions
on Nd of A = 142. 144 and 146.
647
Volume
29B. number
PHISICS
10
18 August 1969
LETTERS
Q=-9.19 140
aye y 142
144
146
Fig. 3. Level schemes obtained from the 142,1~ ldfiN(p,t) reactions. The thick solid lines indicate the strongly excited states.
0
20 _ 40 @CM
DEG
-&+w& @CM
The authors would like to express their thanks to Drs. M. Kondo, I. Miura, A. Shimizu and M. Inoue for their help with the experiment, and to the staff members of the INS cyclotron for their hospitality and cooperation.
Fig. 2. Angular distributions of L = 0 and 2 transitions in the 142.144,146 Nd(p, t) reactions. The smooth curves are drawn to guide the eye. Full circles indicate transitions to the ground-state band. open circles correspond to the pairing vibrational band.
On the other hand, the L = 2 transition to the 3.48 MeV state in 144Nd was strong enough to be compared with the L = 2 transition to the 0.78 MeV state in 140Nd (fig. 2). In the (p, t) reactions on 148Nd and l5oNd, no strong L. = 0 or 2 transitions were observed with Q-values of about -9 MeV. Therefore, the pairing vibrational strength seems to be fragmented such that the simple zero-order picture breaks down for N = 84-88. transition.
*****
648
References A. Bohr.
Proc.
Intern. Symp. Nuclear
structure.
Dubna. 1968; 0. Nathan. Proc. Intern. Symp. Nuclear structure. 1968. K. Yagi et al., Nucl. Instr. Methods 52 (1967) 29; K. Matsuda et al., Nucl. In&r. Methods 53 (1967) 82. K. Yagi et al., Nucl. Phys. A 111 (1968) 129; A 121 (1968) 161; J. Phys. Sot. Japan 24 (1968) 1167. C. N;. Lederer et al. i editors. Table of Isotopes, 6th ed., (John Wiley and Sons, Inc.. 1967) p. 291.