Experimental test of the time stability of the half-life of alpha-decay   Po-214 nuclei
  A method and results of an experimental test of the time stability of the half-life of alpha-decay Po-214 nuclei are presented. Two underground installations aimed at monitoring the time stability have been constructed. Time of measurement exceeds 1038 days for one set up and 562 days for the other. It was found that amplitude of possible annual variation of Po-214 half-life does not exceed 0.2% of the mean value. The limit on the deviation of the decay curve from exponent at 0.034\times T_{1/2}<t< 0.1\times T_{1/2} range has been found. 
E. N. Alexeyev, Ju. M. Gavriljuk, A. M. Gangapshev, A. M. Gezhaev, V.   V. Kazalov, V. V. Kuzminov, S. I. Panasenko, S. S. R...
nucl-ex quant-ph