Based on a theoretical model where the nuclear spins remain unchanged during a collision, we provide an analytical and general expression for the nuclear spin state-to-state distribution of an ultracold diatom-diatom chemical reaction in a magnetic field, for given rotational transitions of the molecules. It simply requires knowledge of the field-dependent eigenfunctions of the molecular reactants and products of the chemical reaction. The final state-to-state distribution drastically changes with the magnetic field. When the distribution is summed over all the final products, a simplified expression is found where only the knowledge of the eigenfunctions of the molecular reactants is required. The present theoretical formalism has been successfully used to explain the magnetic field behavior of the product-state distribution in chemical reactions of ultracold KRb molecules [Hu et al., Nat. Chem. 13, 435 (2021)].

中文翻译：

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磁场中超冷化学反应的核自旋产物状态分布模型

基于碰撞过程中核自旋保持不变的理论模型，我们提供了磁场中超冷硅藻 - 硅藻化学反应的核自旋状态到状态分布的分析和一般表达式，对于给定的旋转跃迁分子。它只需要了解分子反应物和化学反应产物的场相关本征函数。最终的状态间分布随磁场发生剧烈变化。当分布在所有最终产物上求和时，可以找到一个简化的表达式，其中只需要分子反应物的本征函数的知识。等。，纳特。化学 13 , 435 (2021)]。