Keller Thomas, Fabrykiewicz Piotr, Przeniosło Radosław, Sosnowska Izabela, Keimer Bernhard
Max Planck Institute for Solid State Research, Stuttgart, Germany.
Max Planck Society Outstation at the Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM-II), Garching, Germany.
J Appl Crystallogr. 2020 Feb 1;53(Pt 1):88-98. doi: 10.1107/S160057671901611X.
A hitherto unrecognized resolution effect in neutron Larmor diffraction (LD) is reported, resulting from small-angle neutron scattering (SANS) in the sample. Small distortions of the neutron trajectories by SANS give rise to a blurring of the Bragg angles of the order of a few hundredths of a degree, leading to a degradation of the momentum resolution. This effect is negligible for single crystals but may be significant for polycrystalline or powder samples. A procedure is presented to correct the LD data for the parasitic SANS. The latter is accurately determined by the SESANS technique (spin-echo small-angle neutron scattering), which is readily available on Larmor diffractometers. The analysis technique is demonstrated on LD and SESANS data from α-FeO powder samples. The resulting -spacing range agrees with experimental data from high-resolution synchrotron radiation powder diffraction on the same sample.
报道了一种迄今未被认识到的中子拉莫尔衍射（LD）中的分辨率效应，该效应源于样品中的小角中子散射（SANS）。SANS使中子轨迹产生小的畸变，导致布拉格角模糊约百分之几度，从而导致动量分辨率下降。这种效应对于单晶可以忽略不计，但对于多晶或粉末样品可能很显著。提出了一种校正寄生SANS的LD数据的方法。后者通过SESANS技术（自旋回波小角中子散射）精确测定，该技术在拉莫尔衍射仪上很容易获得。对α-FeO粉末样品的LD和SESANS数据进行了分析技术验证。所得的 -间距范围与同一样品的高分辨率同步辐射粉末衍射实验数据一致。
