Alpha Decay of 255No and 257No

The α decay of ²⁵⁵No and ²⁵⁷No produced by ²⁴⁹Cf(¹²C,α2n)²⁵⁵No and ²⁴⁸Cm(¹³C,4n)²⁵⁷No reactions, respectively, has been studied. Five α-particle groups with energies and intensities 8.30 (3%), 8.25 (6%), 8.11 (57%), 7.92 (19%), and 7.76 MeV (15%) were assigned to ²⁵⁵No; and three α-particle groups with energies 8.32, 8.27, and 8.22 MeV to ²⁵⁷No. The half-lives of ²⁵⁵No and ²⁵⁷No were measured to be 200+/-10 and 26 +/- 2 sec, respectively. The decay schemes of ²⁵⁵No and ²⁵⁷No are discussed.