Particle-vibration Coupling Research Articles

Experimental evidence for particle-vibration coupling in 209Pb

Low-lying levels in 209Pb have been studied by means of the reaction 208Pb(d,pγ). Delayed (p,γ) coincidence measurements yield the half-life of the 1422 keV level, τ 1 2 = 1.36 ± 0.30 ns, and an upper limit for the half-life of the 778 keV level, τ 1 2 < 1.0 ns. From these it is concluded that the 778 and 1422 keV levels in 209Pb correspond to the i 11 2 and j 15 2 shell-model states, respectively. The speed of the depopulating E transition from the j 15 2 level is about 16 single-particle units. This enhancement is taken as an evidence for coupling to the collective vibration of 208Pb.

Lower levels of O17 and F17 in the α-model of the nucleus

A method is presented for calculating one-particles states in the α-model by using a non-spherical potential similar to the Nilsson potential but with other properties of symmetry. The spectrum of the lower levels of O17 and F17 is calculated in the weak coupling scheme taking into account the interaction of the motion of the particle with the non-sphericity of the core and with vibrations, which is of essential importance.With certain values of the 2 parameters used in the calculation: the deformation parameter and the particle-vibrational coupling constant, the results are in good agreement with experiment. The lower levels of negative parity of the O17 or F17 system have small reduced widths and are rotational-vibrational states constructed on the single-particle orbits of the outer nucleon 1d and 2s with small admixtures of 1f and 2p. The calculation shows that the quadrupole moment of O17 and the lifetime of the level 12+ are almost entirely determined by the influence of the lower 2+ level of O14 with an energy 6.91 MeV.