Nuclei in the 135 I 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 126 Sb(n, γ ). The nuclear level density and the γ -ray strength function of 127 Sb have been extracted from 124 Sn(α, pγ ) 127 Sb data using the Oslo method. The level density in the low-excitation-energy region agrees well with known discrete levels, and the higherexcitation-energy region follows an exponential curve compatible with the constant-temperature model. The strength function between E γ ≈ 1.5-8.0 MeV presents several features, such as an upbend and a possibly doublepeaked 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 126 Sb(n, γ ) 127 Sb 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.

The γ -ray strength function and the nuclear level density of 167 Ho have been extracted using the Oslo method from a 164 Dy(α, pγ ) 167 Ho experiment carried out at the Oslo Cyclotron Laboratory. The level density displays a shape that is compatible with the constant temperature model in the quasicontinuum, while the strength function shows structures indicating the presence of both a scissors resonance and a pygmy dipole resonance. Using our present results as well as data from a previous 163 Dy(α, pγ ) 166 Ho experiment, the 165 Ho(n, γ ) and 166 Ho(n, γ ) eellian-averaged cross section (MACS) uncertainties have been constrained. The possible influence of the low-lying, long-lived 6 keV isomer 166 Ho in the s process is investigated in the context of a 2M , [Fe/H] = −0.5 asymptotic giant branch star. We show that the newly obtained 165 Ho(n, γ ) MACS affects the final 165 Ho abundance, while the 166 Ho(n, γ ) MACS only impacts the enrichment of 166,167 Er to a limited degree due to the relatively rapid β decay of the thermalized 166 Ho at typical s-process temperatures.

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Sensitivity studies of the i process have identified the region around 135I as a bottleneck for the neutron capture flow. Nuclear properties such as the Maxwellian-averaged cross section (MACS) are key to constrain the uncertainties in the final abundance patterns. From the 124Sn(α, pγ)127Sb reaction we are able to indirectly measure the nuclear level density and γ-ray strength function for 127Sb using the Oslo method. From these two quantities we can calculate the MACS for the 126Sb(n, γ)127Sb reaction using the Hauser-Feshbach formalism, constrain its uncertainties and compare it to libraries such as JINA REACLIB, TENDL and BRUSLIB.

Sensitivity studies of the i process have identified the region around 135I as a bottleneck for the neutron capture flow. Nuclear properties such as the Maxwellian-averaged cross section (MACS) are key to constrain the uncertainties in the final abundance patterns. With the Oslo method, we are able to indirectly measure such properties for the nuclei involved in this process. From the 124Sn(α, pγ)127Sb reaction data we extract the nuclear level density and γ-ray strength function for 127Sb. The level density at higher excitation energies is compatible with the constant-temperature model, while the γ-ray strength function presents features like an upbend and a pygmy-like structure below S n. From these two quantities we can calculate the MACS for the 126Sb(n, γ)127Sb reaction using the Hauser-Feshbach formalism, and constrain its uncerainties from the theoretical ones. Libraries such as JINA REACLIB, TENDL and BRUSLIB agree well with the experimental results, while ENDF/B-VIII.0 predicts a higher rate.