Perturbed Angular Correlation Study of the Static and Dynamic Aspects of Cadmium and Mercury Atoms Inside and Attached to a C-60 Fullerene Cage

Abstract

30 keV Cd-111m and 50 keV Hg-199m beams from ISOLDE were used to implant on preformed targets of C-60 with a thickness of 1 mg cm(-2). Endofullerene compounds, viz. Cd-111m@C-60 and Hg-199m@C-60 formed during implantation were separated by filtration through micropore filter paper followed by solvent extraction. Dried samples of the endofullerene compounds were counted for the time differential perturbed angular correlation (TDPAC) measurement using the coincidence of the 151-245 keV cascade of Cd-111m and the 374 158 keV cascade of Hg-199m on a six LaBr3(Ce) detector system coupled with digital electronics. The results for 111mCd@C60 indicate a single static component (27%) and a fast relaxing component (73%), the latter implying that the cadmium atom moves rapidly inside the cage at room temperature. The quadrupole interaction frequency and asymmetry parameter of the cadmium atom occupying the static site in C60 are omega(Q) = 8.21(36) Mrad s(-1) and eta = 0.41(9), respectively. The fast relaxation constant is 0.0031(4) ns(-1). Similarly, mercury atoms also exhibit a single static and a fast component. The static site has a quadrupole frequency omega(Q) = 283.0(12.4) Mrad s-1 and eta = 0 with a fraction of 30%. The fast relaxation constant is 0.045(8) ns(-1) with a fraction of 70%, very similar to that of cadmium.