Inner hole states in /sup 207/Pb via the /sup 208/Pb(/sup 3/He,. cap alpha. ) /sup 207/Pb reaction at 70 MeV

The /sup 208/Pb(/sup 3/He,..cap alpha..)/sup 207/Pb reaction at 70 MeV incident energy was used to populate hole states up to 28 MeV excitation energy in /sup 207/Pb. A split-pole spectrometer was used for particle analysis and detection. For the excitation energy range between 0 to 4.5 MeV, about eleven well resolved states are excited. These levels contain the main part of the spectroscopic strengths of the 3p/sub 1/2/, 2f/sub 5/2/, 3p/sub 3/2/, 2f/sub 7/2/, 1i/sub 13/2/, and 1h/sub 9/2/ neutron subshells. Three additional regions of enhanced cross sections, centered at 5.5, 8.5, and 14 MeV excitation energy in /sup 207/Pb, are also observed. The 65 keV energy resolution of the present study revealed fine structure in the peak previously observed around 8.5 MeV in /sup 207/Pb. About fifteen levels or groups of levels are populated between 4.5 and 10.5 MeV, and angular distributions have been extracted for each individual peak as well as for the gross structures. A distorted-wave Born-approximation analysis of the data was carried out and shows that the missing l = 3 and 5 strengths in /sup 207/Pb are located in some strong peaks at 5.13, 5.62, and 6.37 MeV. Thus the full sum rule is obtainedmore » for the neutron subshells between N = 126 and N = 82. The highly fragmented peak located at 8.5 MeV excitation energy is shown to arise from 1h/sub 11/2/ neutron pickup. Finally, the large structure, 7 MeV wide and centered around 14 MeV, observed for the first time in this work is tentatively interpreted as arising from neutron pickup from the 1g/sub 9/2/ inner shell. The T/sub greater-than/ components of the deeply-bound state are also observed between 20 to 24 MeV in /sup 207/Pb and therefore from the sum-rule analysis, centroid energies and total strengths for each inner subshell are deduced.« less