Low-lying 130I excited states from the (n, γ) reaction

Abstract

Gamma and conversion electron spectra following the 129I(n, γ) 130I 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 130I 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 129I(d, p) 130I 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.