Hyperfine structure investigation of the (4)f(7)6s(2) S-8(7/2) and 4f(7)6s6p P-6(5/2) states of unstable europium isotope Eu-155

The method of laser induced resonance fluorescence on an atomic beam has be en used in order to measure hyperfine structure splittings of the 4f(7)6s(2 ) S-8(7/2) and 4f(7)6s6p P-6(5/2) levels of the unstable isotope Eu-155. Ex perimental values of magnetic-dipole A- and electric-quadrupole B-constants of Eu-155 have been determined for the first time; A(exp)((EuS7/2)-Eu-155- S-8) = -8.87(22) MHz, A(exp)((EuP5/2)-Eu-155-P-6) = -261(1.2) MHz and B-exp ((EuP5/2)-Eu-155-P-6) -957(12) MHz. After corrections for second-order hype rfine structure perturbations the values: A(corr)((EuP5/2)-Eu-155-P-6) -260 .9(1.2) MHz and B-corr((EuP5/2)-Eu-155-P-6) = -958(12)MHz have been obtaine d and the values of nuclear moments of 155Eu have been estimated: mu(Eu-155 ) = 1.519(10) n.m, and Q(s)(Eu-155) = 2.512(62) b.