Low-lying 128I excited states from the (n, γ) reaction

Abstract Gamma and conversion electron spectra following the 129 I(n, γ) 130 I reaction have been studied with bent crystal and magnetic spectrometers in the energy range 15–1000 keV. Gamma-gamma prompt and delayed coincidences in the range 40–500 keV have been investigated with the use of two Ge(Li) detectors. The 130 I level scheme involving 43 excited states up to 1100 keV has been constructed. Parity is determined for all the levels. Unique spin values are assigned to 29 levels. The half-lives of the 39.952, 69.586, 82.396 and 85.109 keV levels have been measured to be 8.3 ± 1.0 min, 133 ± 7 ns, 315 ±15 ns and 254 ± 4 ns respectively. The neutron binding energy B n was calculated to be 6500.363 ± 0.043 keV. The 129 I(d, p) 130 I reaction has been studied with 22 MeV deuterons at an angle of 40°. The (n, γ) levels are found to match extremely well those from the (d, p) and (n, γ primary ) reactions. A comparison of the (n, γ) and (d, p) levels allowed us to identify the π g 7 2 v s 1 2 , π g 7 2 v d 3 2 , π g 7 2 v h 11 2 and π g 5 2 v h 11 2 two-quasiparticle multiplets. Energy splitting of these p-n configurations by residual interactions taken as a combination of short-range Wigner and singlet forces have been calculated. The presence of the enhanced E2 transitions enabled us to conclude that in the A = 130 region the collective mode of excitation in doubly odd nuclei is as essential as in doubly even nuclei.