Indirect measurement of the (n, gamma) Sb-127 cross section

Nuclei in the I-135 region have been identified as being a possible bottleneck for the i process. Here we present an indirect measurement for the Maxwellian-averaged cross section of Sb-126(n, gamma). The nuclear level density and the gamma-ray strength function of Sb-127 have been extracted from Sn-124(alpha, p gamma) Sb-127 data using the Oslo method. The level density in the low-excitation-energy region agrees well with known discrete levels, and the higher-excitation-energy region follows an exponential curve compatible with the constant-temperature model. The strength function between E-gamma approximate to 1.5-8.0 MeV presents several features, such as an upbend and a possibly double-peaked pygmy-like structure. None of the theoretical models included in the nuclear reaction code TALYS seem to reproduce the experimental data. The Maxwellian-averaged cross section for the Sb-126(n, gamma) Sb-127 reaction has been experimentally constrained by using our level-density and strength-function data as input to TALYS. We observe a good agreement with the JINA REACLIB, TENDL, and BRUSLIB libraries, while the ENDF/B-VIII.0 library predicts a significantly higher rate than our results.