Absence of low-temperature dependence of the decay of {sup 7}Be and {sup 198}Au in metallic hosts

The electron-capture (EC) decay rate of {sup 7}Be in metallic Cu host and the {beta}{sup -}-decay rate of {sup 198}Au in the host alloy Al-Au have been measured simultaneously at several temperatures, ranging from 0.350 K to 293 K. No difference of the half-life of {sup 198}Au between 12.5 K and 293 K is observed to a precision of 0.1%. By utilizing the special characteristics of our double-source assembly, possible geometrical effects that influence the individual rates could be eliminated. The ratio of {sup 7}Be to {sup 198}Au activity thus obtained also remains constant for this temperatures range to the experimental precision of 0.15{+-}0.16%. The resulting null temperature dependence is discussed in terms of the inadequacy of the often-used Debye-Hueckel model for such measurements.