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Electric monopole and quadrupole excitations in 16O
Volume 26B, number 6
ELECTRIC
PHYSICS
MONOPOLE
AND
LETTERS
19 Februarv 1968
QUADRUPOLE
EXCITATIONS
IN
160
M. STROETZEL Institut
fir
Technische
Kemphysik
der
Technischen
Hochschule
Damstadt
Received 2 January 1968
Ground state transition probabilities and transition radii for the levels (Ex in MeV) 6.05(0+), 6.92(23, 9.85(2+), 11.52(2+), 12.05(0+), and 13.1(2+) of 160 as found by (e,e’) experiments are given.
New results are presented in table 1 for positive parity states of 160 obtained by inelastic scattering of electrons at low momentum transfer (qcO.5 fm-l). A detailed description of the experiment will be published elsewhere [l]. Earlier preliminary results [2] for the levels at 6.92 and 11.52 MeV are now slightly improved. In addition, a comment is made concerning the conclusions recently drawn in this journal [3] from the published spectrum of ref. 2. For the O+ level at 12.05 MeV the matrix element ME and the transition radius Rtr are given here for the first time. It was possible to disentangle the monopole part at 6.05 MeV from the strong E3 transition at 6.13 MeV. The monopole matrix element is in good agreement with, but less accurate than, the value ME = 3.80*0.19 fm2 given by Devons et al. [4]. For the evaluation of the transition radius Rtr = 5.4 fm, this value [4] was used together with our measuremerits. The ground-state radiation width of the weak E2 transition to the 9.85 MeV level was obtained by using a transition radius of 3.7 fm. It is in fair agreement with the value 5.9-+0.6 meV found by Larson and Spear [5]. The I$ of the 13.1 MeV level, although only a rough estimate, disagrees with the value 0.6iO.3 eV given in ref. 6. The I$ = 0.66a0.09 eV for the 11.52 MeV level [5] is confirmed by the present measurement. However, the discrepancy between our value and the I?’ = 55 f 15 meV as obtained from resonance f&orescence measurements for the 6.92 MeV level [‘I] is as yet unexplained. Boeker [8,9] has calculated the ME and Rtr for the 6.05 MeV level using wave functions of Brown and Green [lo]. The calculated matrix element (2.6 fm2) is too low, but the transition radius (5.6 fm) agrees well with the experimental value given in table 1. Therefore, the form 376
Table 1 Properties of some positive parity states in 160. The transition radius Rtr is defined, e.g., in refs. 11 and 12. J=
Ex (MeV)
0+
6.05 12.05
___ 4.4oio.44
2+
6.92 9.85 11.52 13.1
93*10 10+4 550 * 70 x 130
FF (meV)
Rtr (fm) *
5.4+0.9 6.OztO.9 3.6+0.4 _-3.8kO.3 ___
* ME in fm2 factor of Boeker [9] for the monopole excitation of the 6.05 MeV level, when normalized to the experimental matrix element [4], is in good agreement with our measurements. Unfortunately the squared monopole form factor [9, fig. 21 differs from that normally adopted by a factor of 22 (=64). If this is realized the disagreement stated by Bishop [3] between our results [2] and the calculation of Boeker vanishes. It would be interesting to calculate the ME and Rtr for the second excited O+ state with the model of ref. 10 and compare the results with those of the 12.05 MeV level given here. I am indebted to Prof. P. Brix and Dr. F. Gudden for their interest and encouragement during this investigation. Valuable discussions with Prof. F. Beck are gratefully acknowledged. The calculations were performed at the Rechenzentrum der Technischen Hochschule Darmstadt. This work was sponsored by the Bundesministerium ftir wissenschaftliche Forschung.
Volume
26B, number
6
PHYSICS
LETTERS
References
19 February
1968
6. I. V. Mitchel and T. R. Ophel, Nuclear Phys. 58 (1964) 529. 7. C. P.Swann and F. R. Metzger, Phys. Rev. 108 (1957) 982. Phys. Letters 21 (1966) 69. 8. E.Boeker, Phys. Letters 24B (1967) 616. 9. E.Boeker, 10. G. E. Brown and A. M. Green, Nuclear Phys. 75 (1966) 401. Z. Phys. 191 (1966) 24. 11. E.Spamer, Z. Phys. 185 (1965) 111. 12. F. Gudden and P.Strehl,
Thesis, Darmstadt 1967; to be pub1. M. Stroetzel, lished in Z. Physik. 2. M. Stroetzel and F. Gudden, Phys. Letters 22 (1966) 485. 3. G. R. Bishop, Phys. Letters 25B (1967) 499. 4. S. Devons, G. Goldring and G. R. Lindsey, Proc. Phys. Sot. 67 (1954) 134. 5. J. D. Larson and R. H. Spear, Nuclear Phys. 56 (1964) 497.
****t
ELECTRIC
PHYSICS
MONOPOLE
AND
LETTERS
19 Februarv 1968
QUADRUPOLE
EXCITATIONS
IN
160
M. STROETZEL Institut
fir
Technische
Kemphysik
der
Technischen
Hochschule
Damstadt
Received 2 January 1968
Ground state transition probabilities and transition radii for the levels (Ex in MeV) 6.05(0+), 6.92(23, 9.85(2+), 11.52(2+), 12.05(0+), and 13.1(2+) of 160 as found by (e,e’) experiments are given.
New results are presented in table 1 for positive parity states of 160 obtained by inelastic scattering of electrons at low momentum transfer (qcO.5 fm-l). A detailed description of the experiment will be published elsewhere [l]. Earlier preliminary results [2] for the levels at 6.92 and 11.52 MeV are now slightly improved. In addition, a comment is made concerning the conclusions recently drawn in this journal [3] from the published spectrum of ref. 2. For the O+ level at 12.05 MeV the matrix element ME and the transition radius Rtr are given here for the first time. It was possible to disentangle the monopole part at 6.05 MeV from the strong E3 transition at 6.13 MeV. The monopole matrix element is in good agreement with, but less accurate than, the value ME = 3.80*0.19 fm2 given by Devons et al. [4]. For the evaluation of the transition radius Rtr = 5.4 fm, this value [4] was used together with our measuremerits. The ground-state radiation width of the weak E2 transition to the 9.85 MeV level was obtained by using a transition radius of 3.7 fm. It is in fair agreement with the value 5.9-+0.6 meV found by Larson and Spear [5]. The I$ of the 13.1 MeV level, although only a rough estimate, disagrees with the value 0.6iO.3 eV given in ref. 6. The I$ = 0.66a0.09 eV for the 11.52 MeV level [5] is confirmed by the present measurement. However, the discrepancy between our value and the I?’ = 55 f 15 meV as obtained from resonance f&orescence measurements for the 6.92 MeV level [‘I] is as yet unexplained. Boeker [8,9] has calculated the ME and Rtr for the 6.05 MeV level using wave functions of Brown and Green [lo]. The calculated matrix element (2.6 fm2) is too low, but the transition radius (5.6 fm) agrees well with the experimental value given in table 1. Therefore, the form 376
Table 1 Properties of some positive parity states in 160. The transition radius Rtr is defined, e.g., in refs. 11 and 12. J=
Ex (MeV)
0+
6.05 12.05
___ 4.4oio.44
2+
6.92 9.85 11.52 13.1
93*10 10+4 550 * 70 x 130
FF (meV)
Rtr (fm) *
5.4+0.9 6.OztO.9 3.6+0.4 _-3.8kO.3 ___
* ME in fm2 factor of Boeker [9] for the monopole excitation of the 6.05 MeV level, when normalized to the experimental matrix element [4], is in good agreement with our measurements. Unfortunately the squared monopole form factor [9, fig. 21 differs from that normally adopted by a factor of 22 (=64). If this is realized the disagreement stated by Bishop [3] between our results [2] and the calculation of Boeker vanishes. It would be interesting to calculate the ME and Rtr for the second excited O+ state with the model of ref. 10 and compare the results with those of the 12.05 MeV level given here. I am indebted to Prof. P. Brix and Dr. F. Gudden for their interest and encouragement during this investigation. Valuable discussions with Prof. F. Beck are gratefully acknowledged. The calculations were performed at the Rechenzentrum der Technischen Hochschule Darmstadt. This work was sponsored by the Bundesministerium ftir wissenschaftliche Forschung.
Volume
26B, number
6
PHYSICS
LETTERS
References
19 February
1968
6. I. V. Mitchel and T. R. Ophel, Nuclear Phys. 58 (1964) 529. 7. C. P.Swann and F. R. Metzger, Phys. Rev. 108 (1957) 982. Phys. Letters 21 (1966) 69. 8. E.Boeker, Phys. Letters 24B (1967) 616. 9. E.Boeker, 10. G. E. Brown and A. M. Green, Nuclear Phys. 75 (1966) 401. Z. Phys. 191 (1966) 24. 11. E.Spamer, Z. Phys. 185 (1965) 111. 12. F. Gudden and P.Strehl,
Thesis, Darmstadt 1967; to be pub1. M. Stroetzel, lished in Z. Physik. 2. M. Stroetzel and F. Gudden, Phys. Letters 22 (1966) 485. 3. G. R. Bishop, Phys. Letters 25B (1967) 499. 4. S. Devons, G. Goldring and G. R. Lindsey, Proc. Phys. Sot. 67 (1954) 134. 5. J. D. Larson and R. H. Spear, Nuclear Phys. 56 (1964) 497.
****t