Nuclear resonance fluorescence inBa136

Abstract

The resonant scattering of electron bremsstrahlung by an enriched sample of ' Ba has been studied for photon energies of up to 5 MeV. It provided estimates of the: radiative widths for 10 levels. Based on the relative yields at scattering angles of 96' and 126, unambiguous spin assignments were made to 5 of these levels. Where feasible, the yield measurements were supplemented by self-absorption data and by linear polarization studies. For the strongest excitation in "Ba, at 3.436 MeV, the resonance fluorescence experiments led to a 1 assignment and a value I 0 = 88+22 meV for the partial width of the ground state transition. The corresponding E1 strength is approximately 1/3 of the El strengths observed for the strongest low-lying E1 transitions in the even-even N = 82 nuclei. When combined with previous observations for N )82, the result obtained for ' Ba (N = 80) indicates that the strengths of the ground state transitions from the lowest 1 states peak at à = 82. Yield information on a few levels in "Ba and " Ba was also obtained. NUCLEAR REACTIONS '3~'3 Ba(p, p) bremsstrahlung 1.68 MeV (E (5.0 MeV; measured 0 (96') and 0 (126'), self-absorption, LP; deduced g I'0 /l, J, x.Enriched Ba target, natural target.

Fine Structure of the Pygmy Dipole Resonance inXe136

“…Therefore, the PDR is a challenge for theory in nuclear physics because one can expect a good description of the fragmentation of a collective mode without including any phenomenological parameters responsible for the resonance width. Thus, the comparison to experimental data makes it possible to determine whether the damping mechanism for a collective mode in many-body systems is well understood.The first evidence for strong low-lying E1 excitations in heavy nuclei located in the energy region 5-10 MeV indicating an additional structure beside the IVGDR in the E1 response of atomic nuclei was found three decades ago [1][2][3]. Recently, an experimental survey of the whole mass region has revealed that the PDR is a common excitation mode in most atomic nuclei [4,5].…”

“…The first evidence for strong low-lying E1 excitations in heavy nuclei located in the energy region 5-10 MeV indicating an additional structure beside the IVGDR in the E1 response of atomic nuclei was found three decades ago [1][2][3]. Recently, an experimental survey of the whole mass region has revealed that the PDR is a common excitation mode in most atomic nuclei [4,5].…”

First identification of dipole excitations to a2+⊗3−⊗particle multiplet in an odd-Zilges1, Herzberg2, Brentano3 et al. 1993Phys. Rev. Lett.441130View full textAdd to dashboardCite

“…As nuclei in the N = 82 region have relatively low lying 3~~ states with very strong (E3; 3~ -» 0+) transitions, many investigations on (2 + (g> 3~) states concentrate on different Ba, Ce, Nd, and Sm isotopes. In photon scattering experiments the 1~~ member of the 2 + ® 3~ multiplet has been found in various N = 82 nuclei [10][11][12][13]. Experimental effort is under way to detect other members of this multiplet with different experimental techniques, but the information is sparse; see, e.g., [14][15][16].…”

Electric dipole strength distribution below the E1 giant resonance in N = 82 nuclei

“…This mode was first observed in neutron capture reactions [1][2][3] and from the beginning of the 1990s it has attracted considerable interest. Recently in the photon scattering experiments in N = 82 semi-magic 136 Xe, 138 Ba, 140 Ce, 142 Nd and 144 Sm nuclei a similar mode has been observed in the energy interval between 5.5 MeV and 8 MeV (see Refs.…”

“…These observations initiated a large number of both experimental and theoretical research into the PDR. A series of subsequent nuclear experiments [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] have shown that this is a common mode in nuclei at excitation energies around 7 MeV. Nowadays this mode has been found for isotopes ranging from the light nuclei (such as 17−22 O) up to lead isotopes including the transitional nuclei [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”