Use of Molecular Dynamics Simulations to Study Signal-to-Noise Aspects for obtaining Polarized Neutron Scattering Cross Sections from Spin-Manipulated Hyperpolarized Molecules in Solution*

We use molecular dynamics (MD) simulations of methyl nicotinate in methanol to calculate angular cross sections of polarized thermal neutrons scattered from hyperpolarized and spin-manipulated molecules (via NMR techniques) in solution.  Methyl nicotinate is a prime candidate because very high nuclear spin hyperpolarization has been attained through polarization transfer from para-hydrogen (1).  Using MD simulations, we study these cross sections on an absolute scale and in the presence of simulated detector noise.  This permits study of combinations of methyl nicotinate concentration, state of polarization, sample size, geometry, neutron flux, experiment duration, detector configuration, and detector efficiency that provide for signals that permit measuring site-site correlation functions between NMR-selected, hyperpolarized methyl nicotinate nuclei.  To do so we use cross sections established for neutron spin-flip and no-spin-flip cases (2).  We study prospects for obtaining useful signals from current neutron scattering sources, suitably configured. 

 

(1) See, for example, P.J. Rayner, et al., PNAS 114 (2017) E3188

(2) M. Kotlarchyk and G.M. Thurston, J. Chem. Phys. 145 (2016) 244201