# Impact of restricted spin-ranges in the Oslo Method: The example of (d,p)$^{240}\mathrm{Pu}$

## TL;DR

This study systematically examines how restricted spin ranges influence the nuclear level density and gamma-ray strength functions obtained via the Oslo Method, emphasizing the importance of accurate spin distribution knowledge.

## Contribution

It demonstrates the significant impact of populated spin distributions on Oslo Method results using a detailed case study of plutonium-240.

## Key findings

- Populated spin distribution critically affects extracted nuclear data.
- Accurate spin distribution knowledge improves reliability of Oslo Method results.
- Monte-Carlo simulations confirm the influence of spin restrictions.

## Abstract

In this paper we present the first systematic analysis of the impact of the populated vs. intrinsic spin distribution on the nuclear level density and $\gamma$-ray strength function retrieved through the Oslo Method. We illustrate the effect of the spin distribution on the recently performed $^{239}\mathrm{Pu}$(d,p$\gamma$)$^{240}\mathrm{Pu}$ experiment using a 12 MeV deuteron beam performed at the Oslo Cyclotron Lab. In the analysis we couple state-of-the-art calculations for the populated spin-distributions with the Monte-Carlo nuclear decay code RAINIER to compare Oslo Method results to the known input. We find that good knowledge of the populated spin distribution is crucial and show that the populated distribution has a significant impact on the extracted nuclear level density and $\gamma$-ray strength function for the $^{239}\mathrm{Pu}$(d,p$\gamma$)$^{240}\mathrm{Pu}$ case.