2001 年 11 巻 4 号 p. 311-314
In the early days of nuclear science, many researchers tried to see if a nuclear decay constant could be changed by putting radioactive nuclei in various extreme environments, such as high and low temperatures, high pressure and high electromagnetic fields. They could not find any measurable change. Since then it was believed that a nuclear decay constant was independent of extranuclear conditions. In 1947, it was pointed out that there might be observable changes in decay constants when decay modes were dominated by an electron capture or an internal conversion process. Thereafter, many experimental studies were carried out, and their changes were observed. We studied the change of the decay constant of 99mTc by applying high-pressure. The present status of our study is described in this report.