Electron-capture decay rate of 7Be encapsulated in a C70 fullerene cage

The decay rate of 7Be electron capture in C70 and Be metal was measured employing a reference method. The half-life (T1/2) of 7Be endohedral C70 (7Be@C70) was found to be T1/2 = 52.49 & PLUSMN; 0.04 d at room temperature (T = 293 K) and T1/2 = 52.42 & PLUSMN; 0.04 d at liquid helium temperature (T = 5 K). Furthermore, the T1/2 of 7Be in Be metal was T1/2 = 53.25 & PLUSMN; 0.04 d at room temperature (T = 293 K) and T1/2 = 53.39 & PLUSMN; 0.03 d at liquid helium temperature (T = 5 K). These values for 7Be@C70 at T = 5 K are approximately 1.6%(1.8%) smaller than those for 7Be in Be metal at T = 293 K (T = 5 K), indicating the difference in the electron wave functions for 7Be inside C70 and 7Be in C60 and Be metal. The average charge transfer from the L(2s) electrons of the 7Be atom influences such variations in the decay constant (& lambda; = ln 2/T1/2) in the environment. The experimental and theoretical investigations revealed that the change in the EC-decay rate of 7Be could be largely related to the potential configurations and the environment inside C60 and/or C70 cages. The motion of 7Be inside cages was found to be restricted according to temperature.

Automated summary

The decay rate of 7Be electron capture in C70 and Be metal was measured and compared. The half-life of 7Be@C70 at room temperature and liquid helium temperature was found to be slightly shorter compared to that of 7Be in Be metal. The difference in the electron wave functions inside C70 and Be metal contributed to this discrepancy.