Direct observation of effective temperature of Ta atom in layer compound TaS₂ by neutron resonance absorption spectrometer

A neutron resonance absorption spectrometer, DOG, has been installed at KENS, High Energy Accelerator Research Organization Neutron Source, which enables us to investigate the motions of a particular element by analyzing the line width of resonance absorption spectrum. We measured the temperature dependence of the effective temperature of Ta motion in TaS₂ as well as in Ta metal using DOG. The effective temperatures extracted from the observed absorption spectrum agree well with the calculated values from the phonon density of states of Ta metal over a wide temperature range of 10 to 300 K. We also succeeded in measuring both the angular dependence and the temperature dependence of effective temperatures of Ta in a layer compound TaS₂. Based on the temperature dependence of the effective temperature, the partial phonon density of states of Ta in TaS₂ was discussed.