Recent Experimental Neutron Resonance Spectroscopy Results as a Test of Statistical Theories of Short and Long Range Order for Level Spacings

Abstract

During 1968 and 1970, we obtained large amounts of high quality neutron resonance spectroscopy data using the Columbia University Nevis Synchrocyclotron. This report emphasizes our experimental results for even-even nuclei having 150 < A < 190. In the oast, attempts to make detailed comparison of experimental resonance energies for nuclei for such “best test” cases as Th²³² or U²³⁸ with theory gave poor fits for those tests which assumed that a single s level population only was present, and were sensitive to the inclusion of a partial extra p level population. For 150 < A < 190, the s level strength function S₀ is sufficiently greater than the p level strength function S₁ that all p levels tend to be weaker than all but a very small fraction of the s levels, providing a better separation of the two populations. Our results for Er^l66, Er^l68, w^l82, w^l84, Sm^l52, and Yb^l72 were of particularly good quality, and give good agreement with the following statistical tests. Except for Er¹⁶⁸, they seem to have only s levels, and for Er¹⁶⁸ the p levels can be cleanly separated out on the basis of their strength.

Research supported in part by the U.S. Atomic Energy Commission.