Motions in proteins occur over a wide range of time scales, from femtoseconds to seconds or longer.¹⁻³ Therefore, their characterization requires the application of a correspondingly wide range of experimental probes. Among these incoherent neutron scattering (INS) is a particularly direct source of information on time scales and forms of hydrogen motions.⁴⁻⁸ However, due to limited accuracy in the measurement of energy changes of scattered neutrons, INS work has been limited to the 10⁻¹⁵-10⁻¹⁰s time scales. The neutron spin-echo technique was developed to overcome this limitation.⁹ Neutron spin-echo allows precise measurement of velocity changes of neutrons via Larmor precession of the neutron’s spin. This has led to the possibility of extracting information on atomic motions on nanosecond and longer time scales.