Isotopic Identification of Neutron Resonances of Cd, Sb, Os, and Pt from Capture Gamma-Ray Spectra

The Argonne fast chopper has been used in conjunction with a 3-variable magnetic-tape recording system to demonstrate the high efficiency and sensitivity of isotopic identification of neutron resonances by observation of capture γ rays. A discussion of features of capture spectra which can be useful in isotopic assignment is presented as well as results for resonances in natural Cd, Sb, Os, and Pt. The experimental study reported emphasizes primarily the observation of coincident γ rays as a means of measuring binding energies and characteristic low-energy lines of nuclides giving rise to resonant capture. The isotopic assignments include 23 resonances in Cd between 18 ev and 235 ev, 6 of which were previously unassigned; 20 resonances in Sb between 5 and 200 ev; 23 resonances in Os in the region between 6 ev and 61 ev; and two previously unresolved resonances at 67 ev assigned to Pt¹⁹⁵. The data lead to observed level spacings of 33 ev in Cd¹¹¹, 80 ev in Cd¹¹², 27 ev in Cd¹¹³, 27 ev in Sb¹²¹, 12 ev in Sb¹²³, and 5.1 ev in Os¹⁸⁹. Strength functions for Cd¹¹¹ and Cd¹¹³ based on the identifications are in agreement with previous reported values. For Os¹⁸⁹, from transmission data previously unreported, the value Γₙ⁰D=(2.0_-0.7+2.2)×10^-4 is obtained.