Radioactive decay speedup at T=5 K: electron-capture decay rate of (7)Be encapsulated in C(60)

• Published in: Physical review letters Vol. 98; no. 25; p. 252501
• Main Authors: Ohtsuki, T, Ohno, K, Morisato, T, Mitsugashira, T, Hirose, K, Yuki, H, Kasagi, J
• Format: Journal Article
• Language: English
• Published: United States 22.06.2007
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PHYSREVLETT.98.252501

The electron-capture (EC) decay rate of (7)Be in C(60) at the temperature of liquid helium (T=5 K) was measured and compared with the rate in Be metal at T=293 K. We found that the half-life of (7)Be in endohedral C(60) ((7)Be@C(60)) at a temperature close to T=5 K is 52.47+/-0.04 d, a value that is 0.34% faster than that at T=293 K. In this environment, the half-life of (7)Be is nearly 1.5% faster than that inside Be metal at room temperature (T=293 K). We then interpreted our observations in terms of calculations of the electron density at the (7)Be nucleus position inside the C(60); further, we estimate theoretically the temperature dependence (at T=0 K and 293 K) of the electron density at the Be nucleus position in the stable center inside C(60). The theoretical estimates were almost in agreement with the experimental observations.