Hyperfine field and fraction in high field site for implanted 221Fr

Abstract A low temperature nuclear orientation study has been performed on Fr in Fe. Anisotropy measurements of both gamma rays and alpha particles have been done. The best value for the hyperfine field, obtained in the gamma-ray experiment, is 129.7(40) T. The results from the alpha-particle experiment support this value. The value is a factor of 2 larger than measured earlier; at present there is no good explanation for this discrepancy. A lower limit of 37% and an upper limit of 45% of Fr in high field site can be set.