A comparative study of troilite in bulk ordinary chondrites Farmington L5, Tsarev L5 and Chelyabinsk LL5 using Mössbauer spectroscopy with a high velocity resolution

Abstract

A comparative study of troilite in bulk ordinary chondrites Farmington L5, Tsarev L5 and Chelyabinsk LL5 was carried out using Mössbauer spectroscopy with a high velocity resolution and two different fitting programs: in the first case the quadrupole interaction was treated as a perturbation to the first order on the nuclear Zeeman levels, whereas in the other case the full static Hamiltonian of the hyperfine interaction (magnetic+quadrupole) was taken into account for the excited and ground nuclear states. The first fit of the Mössbauer spectra revealed a difference between the hyperfine magnetic field values as found for troilite in Farmington L5 (307.7±0.2kOe) and in both Tsarev L5 (311.3±0.3kOe) and Chelyabinsk LL5 (311.9±0.5kOe), although the spectral component of troilite could not be fitted satisfactorily. In contrast, the second fit resulted in a more accurate description of the troilite spectral component, and revealed a difference in the electric field gradient values found for troilite in Farmington L5 (−4.85±0.03×1021V/m2) and in both Tsarev L5 (−4.68±0.05×1021V/m2) and Chelyabinsk LL5 (−4.66±0.04×1021V/m2), while the difference between the hyperfine magnetic field values was less pronounced.