OCTUPOLE DEFORMATION IN SM-149, SM-151 NUCLEI

Parity doublet states and alternating parity bands in Sm-149, Sm-151 n uclei observed in Nd-148, Nd-150(alpha,3ngamma) reactions at E(alpha) = 37 and 35 MeV are presented here. Nineteen new transitions in SM-149 and sixteen in Sm-151 have been observed in singles and gamma-gamma-t -r.f. coincidence experiments. Four alternating parity bands in Sm-149 and two in Sm-151 characterized by simplex quantum numbers are report ed. The observed level schemes are interpreted in terms of octupole de formation. The energy difference due to parity splitting, collective r otational parameters, quasiparticle Routhians, single particle angular momentum alignments of bands with simplex quantum number s = +/-i in Sm-149 and with s = -i in Sm-151 have been calculated from the experim ental results. From the El, E2 branching ratios, the electric dipole m oments are deduced to be [D0] = 0.19 +/- 0.08 e fm for Sm-149 and [D0] = 0.36 +/- 0.11 e fm for Sm-151. The parameter C1, a function of the symmetry energy coefficient, has been estimated for Sm-149 from the li quid drop model of Strutinsky for deformed nucleus, and has been found to be C1 = 0.002 003(+0.000 087/-0.000 159) fm.