# Chemical hydrodynamics of nuclear spin states Source: [Chemical hydrodynamics of nuclear spin states]() Collection index: [llms.txt]() Data updated: 2025-10-25T07:41:49.622Z Authors: Anupama Acharya, Madhukar Said, Sylwia J. Barker, Marcel Utz, Bruno Linclau, Ilya Kuprov Published: 2025-05-04T12:38:10.000Z ## Abstract Quantum mechanical equations of motion are strictly linear in state descriptors, such as wavefunctions and density matrices, but equations describing chemical kinetics and hydrodynamics may be non-linear in concentrations. This incompatibility is fundamental, but special cases can be handled - for example, in magnetic resonance where nuclear spin interactions may be too weak influence concentration dynamics. For processes involving single spins and first-order chemical reactions, this is a well-researched topic, but time evolution of complex nuclear spin systems in the presence of second-order kinetics, diffusion, and flow has so far remained intractable. This creates obstacles in microfluidics, homogeneous catalysis, and magnetic resonance imaging of metabolic processes. In this communication we report a numerically stable formalism for time-domain quantum mechanical description of nuclear spin dynamics and decoherence in the simultaneous presence of diffusion, flow, and second-order chemical reactions. The formalism is implemented in versions 2.11 and later of the open-source Spinach library. As an illustration, we use Diels-Alder cycloaddition of acrylonitrile to cyclopentadiene, yielding endo- and exo-norbornene carbonitrile, in the presence of diffusion and flow in the detection chamber of a microfluidic NMR probe (a finite element model with thousands of Voronoi cells) with a spatially localised stripline radiofrequency coil. ## Recorded benchmark results A research result applies to its stated dataset, split, metric and evaluation configuration. Compare like-for-like settings, preserve the metric's unit and direction, and distinguish paper-reported results from independent reproduction. The best result recorded here is not a claim of exhaustive, current global coverage. ## Original sources and implementation [Original paper]() [PDF]()