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Analog states excited with the 93Nb(p, d)92Nb reaction
Volume 2611. numlwr 11
ANALOG
STATES H. TAKETANI,
PHYSICS
EXCITED
WITH
M. ADACHI, Tokyo
LETTERS
Institute
THE
29 Auril
g3Nb(p,d)g2Nb
M. OGAWA and K. A.SHIBE
of Technology.
Tokyo.
1 April
Japan
1968
Excited stales up to about 13 MeV in g2Nb have been investigated \r+ththe prominent 1n levels at Ex -: 11.54 and 11.80 MeV were found. These are possible 5- and 4- levels in 92Zr. The sum of the transition strengths for with the 21); analog state pick-up strength in the 9OZr(p~ d)89Zr reaction. the (2~$)~ proton configuration in 93Nb is 60 * 12 ‘A.
At an incident proton energy of 55 MeV, the g3Nb(p, d)92Nb reaction has been investigated. Outgoing deuterons were analyzed with a broadrange magnetic spectrometer with a 200-fold propertional counter array along the focal plane [l]. With a typical energy resolution of about 100 keV, the energy spectra and the corresponding angular distributions of deuterons were obtained for the residual nuclear levels up to about 13 MeV excitation. As shown in fig. 1, the deuteron spectra up to about 12 MeV excitation consist of three groups. The first group ranges from 0 to 0.5 MeV and is known [2-41 to be due to the (gl),(d+), configuration. The second ranges from 3 to 5 MeV and is probably due to the coupling of a neutron hole in the N = 50 closed shell to (g;)r. Because of unsatisfactory energy resolution, these two groups could not be analyzed in a quantitative way. The third is that of analog states (11.54 and 11.80 MeV) which, after taking into account the Coulomb displacement energies. were shown to correspond to 2.53 f 0.03 and 2.79 f 0.03 MeV excitation in 92Zr. The probable errors for these energies in 92Zr are expected to be within 100 keV considering the usual discrepancy between the observed energy and the expected one from the Coulomb displacement energy. The doublet splitting 0.26 f 0.04 MeV is more accurate. Angular distributions for these states are shown in fig. 2. We also obtained the angular distribution for the 9OZr(p, d)89Zr reaction [5] leading to the 8.11 MeV analog state ($-) in 89Zr which is shown as a solid curve in the same figure. Since the 8.11 MeV state in 8gZr is known to be a 2~; neutron hole state, the curves show 2, = 1 character. As shown in fig. 2, the two angular distributions for g2Nb are similar in 660
REACTION
Y. YOSHIDA,
Received
1968
g3Nb(p. d)“Nb reaction. TWO attributed to the analogs of the these two states. in comparison implies that the percentage of
shape to that for 8g Zr and the sum of the cross sections is close to that of the latter, suggesting that these levels in 92Nb are also due to 21~ pick-up. This suggests that the two analog states found at 11.54 and 11.80 MeV are 5- and 4- levels due to a 2p neutron hole coupled with a g; proton. This in turn predicts the existence of 5- and 4- levels at around 2.53 and 2.79 MeV in g2Zr. The (2Jf + 1) intensity rule suggests that the 2.53 MeV state has 6 = 5- and the 2.79 MeV state 4-.
--Exciia
12
tlon 8
(MeV)-
Energy
4
0
2000 T = 6 Analogs II.80
0
Il.54
50
150
IO0 COUNTER
NUMBER
Fig. 1. The deuteron spectrum from the 93Nb(p, d)92Nb reaction.
Volume 26B.
PHYSICS
number 11
LETTERS
1968
In fact, most of the even Zr isotopes have 5and 4- levels at around 2.5 MeV excitation. These levels are known to be due to the (g;),(2p+), configuration. At present there are no ‘5- or 4- levels known in the corresponding energy region of g2Zr. The ratio of the sum of the cross sections for these two states to that for the 9OZr(p.d)69Zrg_lI reaction together with the French-Macfarlane sum rule [S] for the higher T state, gives the probability of the (2p+)2 proton configuration in 93Nb with respect to that in 9OZr. If we take the currently accepted values [7] of 63W for the probability in gOZr, the corresponding value in the ground state of 93Nb becomes 60 * 12%.
‘“Nb( p,d)‘*Nb
IA
29 April
4. IlS4Mw state $. I P30MeV state
1
-0.51xagZr (8.1 I MeVI
The authors would like to thank K. Manabe, K. Mizusawa, H. Nakayama and T. Toriyama for their help in data taking and the INS-cyclotron crew for the operation of the cyclotron.
References 1. K.Yagi.
2.
3. 4. Fig. 2. Data points show the differential cross sections leading to the 11.54 and 11.80 MeV states in 92Nb. Solid curves show the experimental angular distribution of deuterons in the 90Zr(p, dj89Zr reaction leading to the 8.11 MeV state of 89Zr multiplied by appropriate factors.
5. 6. 7.
H.Oga\va. Y.Ishizaki. T.Ishimatsu, J. Kokame and K. Matsuda. Nucl. Inst. and Meth. 52 (1967) 82. R. K. Sheline. C. Watson and E. W. Hamburger. Phys. Letters 8 (1964) 121. R. F. SQeet, K. H. Bhatt and J. 8. Ball. Phys. Letters 8 (1964) 131. J.R.Ball and M.R.Cates. Phys.Letters 25B (1967) 126. H. Taketani et al.. to be published. A preliminaq account was presented at the Intern.Conf.on Nuclear structure (Tokyo. Sept. 1967) as contributed No. 4.78. J.B.French and M.H.Macfarlane. Nucl.Phgs.26 (1961) 168. J.Vervier. Nucl.Phys. 75 (1966) 17.
*****
661
ANALOG
STATES H. TAKETANI,
PHYSICS
EXCITED
WITH
M. ADACHI, Tokyo
LETTERS
Institute
THE
29 Auril
g3Nb(p,d)g2Nb
M. OGAWA and K. A.SHIBE
of Technology.
Tokyo.
1 April
Japan
1968
Excited stales up to about 13 MeV in g2Nb have been investigated \r+ththe prominent 1n levels at Ex -: 11.54 and 11.80 MeV were found. These are possible 5- and 4- levels in 92Zr. The sum of the transition strengths for with the 21); analog state pick-up strength in the 9OZr(p~ d)89Zr reaction. the (2~$)~ proton configuration in 93Nb is 60 * 12 ‘A.
At an incident proton energy of 55 MeV, the g3Nb(p, d)92Nb reaction has been investigated. Outgoing deuterons were analyzed with a broadrange magnetic spectrometer with a 200-fold propertional counter array along the focal plane [l]. With a typical energy resolution of about 100 keV, the energy spectra and the corresponding angular distributions of deuterons were obtained for the residual nuclear levels up to about 13 MeV excitation. As shown in fig. 1, the deuteron spectra up to about 12 MeV excitation consist of three groups. The first group ranges from 0 to 0.5 MeV and is known [2-41 to be due to the (gl),(d+), configuration. The second ranges from 3 to 5 MeV and is probably due to the coupling of a neutron hole in the N = 50 closed shell to (g;)r. Because of unsatisfactory energy resolution, these two groups could not be analyzed in a quantitative way. The third is that of analog states (11.54 and 11.80 MeV) which, after taking into account the Coulomb displacement energies. were shown to correspond to 2.53 f 0.03 and 2.79 f 0.03 MeV excitation in 92Zr. The probable errors for these energies in 92Zr are expected to be within 100 keV considering the usual discrepancy between the observed energy and the expected one from the Coulomb displacement energy. The doublet splitting 0.26 f 0.04 MeV is more accurate. Angular distributions for these states are shown in fig. 2. We also obtained the angular distribution for the 9OZr(p, d)89Zr reaction [5] leading to the 8.11 MeV analog state ($-) in 89Zr which is shown as a solid curve in the same figure. Since the 8.11 MeV state in 8gZr is known to be a 2~; neutron hole state, the curves show 2, = 1 character. As shown in fig. 2, the two angular distributions for g2Nb are similar in 660
REACTION
Y. YOSHIDA,
Received
1968
g3Nb(p. d)“Nb reaction. TWO attributed to the analogs of the these two states. in comparison implies that the percentage of
shape to that for 8g Zr and the sum of the cross sections is close to that of the latter, suggesting that these levels in 92Nb are also due to 21~ pick-up. This suggests that the two analog states found at 11.54 and 11.80 MeV are 5- and 4- levels due to a 2p neutron hole coupled with a g; proton. This in turn predicts the existence of 5- and 4- levels at around 2.53 and 2.79 MeV in g2Zr. The (2Jf + 1) intensity rule suggests that the 2.53 MeV state has 6 = 5- and the 2.79 MeV state 4-.
--Exciia
12
tlon 8
(MeV)-
Energy
4
0
2000 T = 6 Analogs II.80
0
Il.54
50
150
IO0 COUNTER
NUMBER
Fig. 1. The deuteron spectrum from the 93Nb(p, d)92Nb reaction.
Volume 26B.
PHYSICS
number 11
LETTERS
1968
In fact, most of the even Zr isotopes have 5and 4- levels at around 2.5 MeV excitation. These levels are known to be due to the (g;),(2p+), configuration. At present there are no ‘5- or 4- levels known in the corresponding energy region of g2Zr. The ratio of the sum of the cross sections for these two states to that for the 9OZr(p.d)69Zrg_lI reaction together with the French-Macfarlane sum rule [S] for the higher T state, gives the probability of the (2p+)2 proton configuration in 93Nb with respect to that in 9OZr. If we take the currently accepted values [7] of 63W for the probability in gOZr, the corresponding value in the ground state of 93Nb becomes 60 * 12%.
‘“Nb( p,d)‘*Nb
IA
29 April
4. IlS4Mw state $. I P30MeV state
1
-0.51xagZr (8.1 I MeVI
The authors would like to thank K. Manabe, K. Mizusawa, H. Nakayama and T. Toriyama for their help in data taking and the INS-cyclotron crew for the operation of the cyclotron.
References 1. K.Yagi.
2.
3. 4. Fig. 2. Data points show the differential cross sections leading to the 11.54 and 11.80 MeV states in 92Nb. Solid curves show the experimental angular distribution of deuterons in the 90Zr(p, dj89Zr reaction leading to the 8.11 MeV state of 89Zr multiplied by appropriate factors.
5. 6. 7.
H.Oga\va. Y.Ishizaki. T.Ishimatsu, J. Kokame and K. Matsuda. Nucl. Inst. and Meth. 52 (1967) 82. R. K. Sheline. C. Watson and E. W. Hamburger. Phys. Letters 8 (1964) 121. R. F. SQeet, K. H. Bhatt and J. 8. Ball. Phys. Letters 8 (1964) 131. J.R.Ball and M.R.Cates. Phys.Letters 25B (1967) 126. H. Taketani et al.. to be published. A preliminaq account was presented at the Intern.Conf.on Nuclear structure (Tokyo. Sept. 1967) as contributed No. 4.78. J.B.French and M.H.Macfarlane. Nucl.Phgs.26 (1961) 168. J.Vervier. Nucl.Phys. 75 (1966) 17.
*****
661