A perturbed angular correlation spectrometer for material science studies

摘要

A four-detector perturbed angular correlation (PAC) spectrometer has been developed with ultra-fast BaF_2 detectors to acquire four coincidence spectra simultaneously, two at 180° and two at 90°. This spectrometer has double efficiency compared to that of a three-detector set-up. Higher efficiency is desirable for PAC studies in solid state physics where large number of coincidences are required to obtain the PAC spectra with good statistics and is particularly useful when the half-lives of the parent probe nuclei used for PAC measurements are ～2-3 days or less as in ~(111)In (2.8 d), ~(99)Mo (2.7 d) and ~(140)La (1.7 d). The performance of the spectrometer has been tested for the HfC>2 monoclinic crystal in the temperature range from 77 to 873 K and for the HfF_4·3H_2O crystal at room temperature. The polycrystalline HfO_2 has been synthesized from Hf metal by heating in air. The hydrated hafnium fluoride has been crystallized by dissolving Hf metal in 40% HF and drying slowly at room temperature.