Abstract
Fission-fragment angular distributions were measured in the reaction of40Ar with208Pb near the fusion barrier. For nearly symmetric mass-/charge splits we find angular distributions symmetric around θ=90 degrees, however, with unusually large anisotropies. These develop gradually into forward-backward asymmetric distributions as one moves away from mass-/charge symmetry. This indicates that non-compound fission (‘quasi-fission’) competes with true fusion-fission. The relative contribution of quasi-fission to the total fission cross section is somewhere between 51 and 85%. In the framework of the extra-push model this is equivalent to an extra-extra push energy for compound-nucleus formation inside the true fission saddle point of 4<E xx <9 MeV in agreement with a recent empirical parametrization of fusion-barrier shifts based on fusion-fission cross sections. On the basis of cross sections for fusion-evaporation residues it had previously been concluded that fusion of40Ar with Pb isotopes occurs unhindered. Possible reasons for this apparent discrepancy are discussed.
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Bock, R., Chu, Y.T., Dakowski, M., Gobbi, A., Grosse, E., Olmi, A., Sann, H., Schwalm, D., Lynen, U., Müller, W.F.J., Bjørnholm, S., Esbensen, H., Wölfli, W., Morenzoni, E.: Nucl. Phys. A388, 334 (1982)
Töke, J., Bock, R., Dai, G.X., Gobbi, A., Gralla, S., Hildenbrand, K.D., Kuzminski, J., Müller, W.F.J., Olmi, A., Stelzer, H., Back, B.B., Bjørnholm, S.: Nucl. Phys. A440, 7 (1985)
Lützenkirchen, K., Kratz, J.V., Wirth, G., Brüchle, W., Dörr, L., Sümmerer, K., Lucas, R., Poitou, J., Grégoire, C., Bjørnholm, S.: Z. Phys. A — Atoms and Nuclei320, 529 (1985)
Lebrun, C., Hanappe, F., Lecolley, J.F., Levebvres, F., Ngô, C., Péter, J., Tamain, B.: Nucl. Phys. A321, 207 (1979)
Borderie, B., Berlanger, M., Gardès, D., Hanappe, F., Nowicki, L., Péter, J., Tamain, B., Agarwal, S., Girard, J., Grégoire, C., Matuszek, J., Ngô, C.: Z. Phys. A — Atoms and Nuclei299, 263 (1981)
Zheng, Z., Borderie, B., Gardes, D., Gauvin, H., Hanappe, F., Péter, J., Rivet, M.F., Tamain, B., Zaric, A.: Nucl. Phys. A422, 447 (1984)
Back, B.B., Clerc, H.-G., Betts, R.R., Glagola, B.G., Wilkins, B.D.: Phys. Rev. Lett.46, 1068 (1981)
Back, B.B., Betts, R.R., Cassidy, K., Glagola, B.G., Gindler, J.E., Glendenin, L.E., Wilkins, B.D.: Phys. Rev. Lett.50, 818 (1983)
Lesko, K.T., Gil, S., Lazzarini, A., Metag, V., Seamster, A.G., Vandenbosch, R.: Phys. Rev. C27, 2999 (1983)
Tsang, M.B., Utsonomiya, H., Gelbke, C.K., Lynch, W.G., Back, B.B., Saini, S., Baisden, P.A., McMahan, M.A.: Phys. Lett. B129, 18 (1983)
Tsang, M.B., Ardouin, D., Gelbke, C.K., Lynch, W.G., Xu, Z.R., Back, B.B., Betts, R.R., Saini, S., Baisden, P.A., McMahan, M.A.: Phys. Rev. C28, 747 (1983)
Back, B.B., Betts, R.R., Gindler, J.E., Wilkins, B.D., Saini, S., Tsang, M.B., Gelbke, C.K., Lynch, W.G., McMahan, M.A., Baisden, P.A.: Phys. Rev. C32, 195 (1985)
Töke, J., Bock, R., Dai, G.X., Gobbi, A., Gralla, S., Hildenbrand, K.D., Kuzminsky, J., Müller, W.F.J., Olmi, A., Reisdorf, W., Bjørnholm, S., Back, B.B.: Phys. Lett.142B, 258 (1984)
Freifelder, R., Prakash, M., Alexander, J.M.: Phys. Rep.133, 315 (1986)
Bond, P.D.: Phys. Rev. Lett.52, 414 (1984)
Bond, P.D.: Phys. Rev. C32, 471 (1985); Phys. Rev. C32, 483 (1985)
Rossner, H.H., Huizenga, J.R., Schröder, W.U.: Phys. Rev. Lett.53, 38 (1984)
Saddle or scission: The Point for Decision. Symposium on Fission Mechanisms, ACS Annual Meeting, Chicago, Illinois, Sept. 8–13 (1985)
Back, B.B.: Phys. Rev. C31, 2104 (1985)
Swiatecki, W.J.: Phys. Scr.24, 113 (1981)
Bjørnholm, S., Swiatecki, W.J.: Nucl. Phys. A391, 471 (1982)
Lützenkirchen, K., Kratz, J.V., Wirth, G., Brüchle, W., Sümmerer, K., Lucas, R., Poitou, J., Grégoire, C.: Nucl. Phys. A452, 351 (1986)
Døssing, Th., Randrup, J.: Phys. Lett.155B, 333 (1985)
Gäggeler, H., Sikkeland, T., Wirth, G., Brüchle, W., Bögl, W., Franz, G., Herrmann, G., Kratz, J.V., Schädel, M., Sümmerer, K., Weber, W.: Z. Phys. A — Atoms and Nuclei316, 291 (1984)
Sahm, C.-C., Clerc, H.-G., Schmidt, K.-H., Reisdorf, W., Armbruster, P., Hessberger, F.P., Keller, J.G., Münzenberg, G., Vermeulen, D.: Z. Phys. A — Atoms and Nuclei319, 113 (1984); Nucl. Phys. A441, 316 (1985)
Clerc, H.-G., Keller, J.G., Sahm, C.-C., Schmidt, K.-H., Schulte, H., Vermeulen D.: Nucl. Phys. A419, 571 (1984)
Poitou, J., Lucas, R., Girard, J., Nifenecker, H.: Nucl. Instrum. Methods153, 181 (1978)
Viola, V.E., Seaborg, G.T.: J. Inorg. Nucl. Chem.28, 697 (1966)
Freiesleben, H., Kratz, J.V.: Phys. Rep.106, 1 (1984)
Cohen, S., Plasil, F., Swiatecki, W.J.: Ann. Phys. (NY)82, 557 (1974)
Sahm, C.-C., Schulte, H., Vermeulen, D., Keller, J.G., Clerc, H.-G., Schmidt, K.-H., Hessberger, F.P., Münzenberg, G.: Z. Phys. A — Atoms and Nuclei297, 241 (1980)
Hessberger, F.P., Münzenberg, G., Hofmann, S., Reisdorf, W., Schmidt, K.-H., Schött, H.J., Armbruster, P., Hingmann, R., Thuma, B., Vermeulen, D.: Z. Phys. A — Atoms and Nuclei321, 317 (1985)
Reisdorf, W., Hessberger, F.P., Hildenbrand, K.D., Hofmann, S., Münzenberg, G., Schmidt, K.-H., Schneider, J.H.R., Schneider, W.F.W., Sümmerer, K., Wirth, G., Kratz, J.V., Schlitt, K.: Nucl. Phys. A438, 212 (1985)
Reisdorf, W., Hessberger, F.P., Hildenbrand, K.D., Hofmann, S., Münzenberg, G., Schmidt, K.-H., Schneider, W.F.W., Sümmerer, K., Wirth, G., Kratz, J.V., Schlitt, K., Sahm, C.-C.: Nucl. Phys. A444, 154 (1985)
Bass, R.: In: Deep-inelastic and fusion reactions with heavy ions. Oertzen, W. von (ed.), p. 287. Berlin, Heidelberg, New York: Springer 1980
Reissdorf, W.: Scientific Report 1980, GSI-81-2, Gesellschaft für Schwerionenforschung, Darmstadt, 1981, p. 73
Reisdorf, W.: Z. Phys. A — Atoms and Nuclei300, 227 (1981)
Reisdorf, W., Töke, J.: Z. Phys. A — Atoms and Nuclei302, 183 (1981)
Keller, J.G.: Doctoral Thesis, TH Darmstadt, Report GSI-85-2 (1985)
Keller, J.G., Schmidt, K.-H., Hessberger, F.P., Münzenberg, G., Reisdorf, W., Clerc, H.-G., Sahm, C.-C.: Nucl. Phys. A452, 173 (1986)
Nörenberg, W.: Lectures presented at the International Summer School on Nuclear Dynamics, Dronten, The Netherlands, 4–17 August 1985, Report GSI-85-48 (1985); Berdichevski, D., Lukasiak, A., Nörenberg, W., Reisdorf, W.: (to be published)
Schmidt, K.-H., Faust, W., Münzenberg, G., Reisdorf, W., Clerc, H.-G., Vermeulen, D., Lang, W.: Proceedings of the International Symposium on Physics and Chemistry of Fission, Jülich, 1979, vol. I (IAEA, Vienna, 1980) p. 409
Glässel, P., von Harrach, D., Civelekoglu, Y., Männer, R., Specht, H.J., Wilhelmy, J.B.: Phys. Rev. Lett.43, 1483 (1979)
Døssing, Th., Randrup, J.: Nucl. Phys. A433, 215 (1985); Nucl. Phys. A433, 280 (1985)
Gäggeler, H., Iljinov, A.S., Popeko, G.S., Seidel, W., Ter-Akopian, G.M., Tretyakova, S.P.: Z. Phys. A — Atoms and Nuclei289, 415 (1979)
Blocki, J.P., Feldmeier, H., Swiatecki, W.J., Preprint GSI-86-16, May 1986. Nucl. Phys. A (submitted for publication)
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The authors are indepted to L. Dörr, E. Jäger, and E. Schimpf for technical assistance, and to W. Reisdorf for his advice concerning the use of the code HIVAP. We enjoyed valuable discussions with Drs. B.B. Back and H. Gäggeler concerningE xx -scaling. This work was supported by a grant from the Bundesministerium für Forschung und Technologie, Federal Republic of Germany.
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Keller, H., Lützenkirchen, K., Kratz, J.V. et al. Evidence for quasi-fission in40Ar+208Pb collisions near the coulomb-barrier. Z. Physik A - Atomic Nuclei 326, 313–326 (1987). https://doi.org/10.1007/BF01297586
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DOI: https://doi.org/10.1007/BF01297586