Competition of isoscalar and isovector proton-neutron pairing in nuclei
Abstract We use shell model techniques in the complete pf shell to study pair correlations in nuclei. Particular attention is paid to the competition of isoscalar and isovector proton-neutron pairing modes which is investigated in the odd-odd N = Z nucleus 46 V and in the chain of even Fe-isotopes. We confirm the dominance of isovector pairing in the ground states. An inspection of the level density and pair correlation strength in 46 V, however, shows the increasing relative importance of isoscalar correlations with increasing excitation energy. In the Fe-isotopes we find the expected strong dependence of the proton-neutron isovector pairing strength on the neutron excess, while the dominant J = 1 isoscalar pair correlations scale much more gently with neutron number. We demonstrate that the isoscalar pair correlations depend strongly on the spin-orbit splitting.
Isovector pairing in odd-A proton-rich nuclei
Abstract A simple model based on the group SO(5) suggests that both the like-particle and neutron-proton components of isovector pairing correlations in odd- A nuclei are Pauli blocked. The same effect emerges from Monte Carlo Shell-model calculations of proton rich nuclei in the full fp shell. There are small differences between the two models in their representation of the effects of an odd nucleon on the competition between like-particle and neutron-proton pairing, but they can be understood and reduced by using a two-level version of the SO(5) model. On the other hand, in odd-odd nuclei with N ≠ Z , SO(5) disagrees more severely with the shell model because it incorrectly predicts ground-state isospins. The shell model calculations for any fp -shell nuclei can be extended to finite temperature, where they show a decrease in blocking.
From the World Literature
LIST OF ILLUSTRATIONS ix ACKNOWLEDGMENTS xi INTRODUCTION: Goethe Coins a Phrase 1 PART ONE: CIRCULATION Chapter 1: Gilgamesh's Quest 39 Chapter 2: The Pope's Blowgun 78 Chapter 3: From the Old World to the Whole World 110 PART TWO: TRANSLATION Chapter 4: Love in the Necropolis 147 Chapter 5: The Afterlife of Mechthild von Magdeburg 170 Chapter 6: Kafka Comes Home 187 PART THREE: PRODUCTION Chapter 7: English in the World 209 Chapter 8: Rigoberta Menchu in Print 231 Chapter 9: The Poisoned Book 260 CONCLUSION: World Enough and Time 281 BIBLIOGRAPHY 305 INDEX 319