Neutron capture γ-rays from 192Ir and 194Ir

Abstract

The reactions 191Ir(n,γ) 192Ir and 193Ir(n, γ) 194Ir with reactor neutrons have been investigated in order to get information on the nuclei 192Ir and 194Ir. The high-energy γ-ray spectra measured with a Ge(Li)-NaI(Tl) pair spectrometer give 123 transitions in 192Ir and 106 transitions in 194Ir leading to levels between the ground states and 1700 keV of excitation energy. The neutron binding energy of 194Ir is B n = 6066.1 ± 1.5 keV. The 192Ir ground state transition cannot be measured because of its high multipolarity. There is evidence that the highest energy transition goes to the 58 keV 1 + excited state. The neutron binding energy is then B n = 6198.7 ± 2.0 keV. The proposed level schemes are based on these binding energy values. Some additional information has been extracted on the 32 ms isomeric state in 194Ir. Low-energy spectra up to 500 keV have been measured with single Ge(Li) detectors. The 192Ir high-energy spectrum taken with a cadmium-filtered neutron beam shows large intensity changes compared to the thermal-capture spectrum.