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Published byJosephine Hawkins Modified about 1 year ago

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With five Appendices at the end

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Deformed nuclei So far, we have dealt with spherical nuclei only. How do we describe deformed nuclei? We need two parameters to describe shape: the amount of deformation, and the axial symmetry.

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What is different about deformed nuclei? OK, sure, the fact that they aren’t spherical !! But what else? Ans: They can ROTATE

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Prolate (+1, -2)Oblate (+2, -1) Max. Asymm.

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This is the essence of the Nilsson model and diagram. Just repeat this idea for EACH j-orbit of the spherical shell model. Look at the left and you will see these patterns. There is only one other ingredient needed. Note that some of the lines are curved ! What does this mean? Where does that come from?

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Detour on 2-state mixing Suppose we have a Hamiltonian H = H 0 + H resid. where H 0 has a set of eigenstates X i The eigenstates of H will therefore be mixtures of those of H 0, that is linear combinations of the X i with coefficients C i. ( In our case, H 0 will be the Hamiltonian of the SPHERICAL shell model that we have been discussing. H resid. will be the terms that change things because the nucleus is deformed.) To understand the effects of these terms, we need to briefly discuss a topic of much wider and fundamental importance: 2- state mixing –with a brief excursion to multi-state mixing

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This is the main result we will need but I include a bit more here and a fuller discussion in an Appendix because the topic is of such fundamental importance.

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Not much is more important than this idea. Please remember it and think about it often (and try to develop a deep love for it). A illustrative special case of fundamental importance Special case of the utmost importance. Mixing of degenerate levels T This is the origin of collectivity in nuclei. Essential also for understanding masses

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Uh-oh, is something wrong with all this?

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Discussed in 9 added slides in the Appendix at the end

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Now add rotation as well for full description of odd- A deformed nuclei. Look at e-e nuclei first. Now use this idea for odd-A nuclei: [ - K ( K + 1)]

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One more example

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Coriolis effects in a rotating body (e.g., earth, nucleus) Notice that the Coriolis effect is equivalent to a tilting of the orbit axis

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Examples Rivers are eroded more on one side than the other Astronauts fixing things in space Continental drift Nuclei --- Yaaaaay !!!

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J j R Rotational motion in odd-A nuclei and the origin of the Coriolis force

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Some formalities Very roughly: Increases with angular momentum, J

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UPO

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J matrix elements are also typically 6 for the UPOs

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Two effects of Coriolis force Diagonal --- energies Off-diagonal --- mixing of Nilsson wave functions

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This gives an extra, diagonal, term in the energy expression for rotational bands with K = ½. Note that the effect alternates with spin, leading to a staggering of rotational energies

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Off diagonal mixing effects of the Coriolis interaction

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Unassigned levels !

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Five Appendices

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Appendix A with more examples of how to use the Nilsson Model in practice

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On the next slides are other that you can look through and see if you understand.

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APPENDIX B on 2-state mixing Suppose we have a Hamiltonian H = H 0 + H resid. where H 0 has a set of eigenstates X i The eigenstates of H will be mixtures of those of H 0 – linear combinations of the X i with coefficients C i. ( In our case, H 0 will be the Hamiltonian of the SPHERICAL shell model. H resid. will be the terms that change things because the nucleus is deformed.) To understand the effects of these terms, we need to briefly discuss a topic of much wider and fundamental importance: 2- state mixing –with a brief excursion to multi-state mixing

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This is the main result we will need but I include a more general discussion because the topic is of such fundamental importance. I will skip several of the next slides but I URGE you to study them.

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Not much is more important than this idea. Please remember it and think about it often (and try to come to love it). A illustrative special case of fundamental importance Special case of the utmost importance. Mixing of degenerate levels T This is the origin of collectivity in nuclei. Essential also for understanding masses

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Appendix C on one of the mysterious (i.e., almost unknown) aspects of rotational motion in odd-A deformed nuclei

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Appendix D on a more formal derivation of the Nilsson Model with emphasis on the small and large deformation limits and quantum numbers

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Appendix E Misc. Coriolis slides

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