An accurate redetermination of the 118Sn binding energy

The energy of well-known strong gamma line from Au-198, the "gold standard", has been modified in the light of new adjustments in the fundamental constants and the value of 411.80176(12) keV was determined, which is 0.29eV lower than the latest 1999 value. An energy calibration procedure for determining the neutron binding energy, B-n from complicated (n, gamma) spectra has been developed. A mathematically simple minimization function consisting only of terms having as parameters the coefficients of the energy calibration curve (polynomial) is used. A priori information about the relationships among the energies of different peaks on the spectrum is taken into account by a Monte-Carlo simulation. The procedure was used in obtaining B-n for Sn-118. The gamma-ray spectrum from thermal neutron radiative capture by Sn-117 has been measured on the IBR-2 pulsed reactor. gamma-rays were detected by a 72 cm(3) HPGe detector. For a better determination of B-n it was important to determine B-n for (CU)-C-64. This value was obtained from two gamma-spectra. One spectrum was measured on the IBR-2 by the same detector. The other spectrum was measured with a pair spectrometer at the Brookhaven High Flux Beam Reactor. From these two spectra, B-n for (CU)-C-64 was determined to be equal to 7915.52(8) keV. This result essentially differs from the previous value of 7915.96(11) keV. The mean value of the two most precise results of the B-n for Sn-118, was determined to be 9326.35(9) keV. The B-n for Fe-57 was determined to be 7646.08(9) keV. (C) 2002 Elsevier Science B.V. All rights reserved.