Neutron photocrystallography: simulation and experiment

TL;DR

This paper introduces neutron photocrystallography, combining experimental neutron diffraction with simulation tools to study light-induced structural changes in crystals, exemplified by nitrosyl linkage-isomers in a specific compound.

Contribution

It presents a new experimental setup at a neutron diffractometer and a simulation tool within JANA2006 for planning photocrystallographic experiments.

Findings

Successful structural determination of photoinduced isomers.

Enhanced reliability through in-situ optical transmission measurements.

Simulation tool aids in experiment planning and feasibility assessment.

Abstract

The investigation of light-induced structural changes by diffractive methods has improved much in the last two decades. We present here the case of neutron photocrystallography for which we have built a special experimental setup at the single crystal neutron diffractometer TriCS at the Swiss Spallation Neutron Source SINQ. We illustrate the progress of the method on the example of the structural determination of photoinduced nitrosyl linkage-isomers in Na2[Fe(CN)5NO] 2H2O. The in-situ determination of the population of the light-induced linkage isomers by optical transmission measurements enhances the reliability of such structural investigations considerably. Additionally we present a new simulation tool within the program package JANA2006 which allows to plan a photocrystallographic experiment thoroughly since the required q-range, the minimally needed population of the photoinduced species, as well as the necessary counting statistics for a successful single crystal diffraction experiment can be evaluated in advance.