Abstract

The need for data-scaling has become increasingly evident as time-resolved pump-probe photocrystallography is rapidly developing at high intensity X-ray sources. Several aspects of the scaling of data sets collected at synchrotrons, XFELs (X-ray Free Electron Lasers) and high-intensity pulsed electron sources are discussed. They include laser-ON/laser-OFF data scaling, inter- and intra-data set scaling.

Highlights

  • With the increasing application of pump-probe photocrystallography over a range from milliseconds to femtoseconds, sample crystals have increasingly needed to be replaced due to laser-induced radiation damage

  • X-ray induced damage is dominant in femtosecond experimentation as performed at X-ray free electron laser (XFEL) sources and high brightness electron diffraction facilities, leading the sample to explode immediately after the generation of a diffraction pattern

  • In the time-resolved synchrotron experiment, it is feasible to collect laser-ON and laserOFF frames in rapid succession, making sure that crystal quality and other conditions, such as incident beam intensity or crystal size, are the same, This eliminates the need for relative scaling of the ON and OFF frames which is otherwise necessary for calculation of the ratios in expression 2b, following expression (5). This is not the case when radiation damage becomes excessive at XFEL sources

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Summary

INTRODUCTION

With the increasing application of pump-probe photocrystallography over a range from milliseconds to femtoseconds, sample crystals have increasingly needed to be replaced due to laser-induced radiation damage. X-ray induced damage is dominant in femtosecond experimentation as performed at X-ray free electron laser (XFEL) sources and high brightness electron diffraction facilities, leading the sample to explode immediately after the generation of a diffraction pattern. The subsequent analysis must be based on multi-crystal data sets, which implies that data-scaling becomes a crucial aspect of the processing of the data, as has been recognized in many reported studies, see, for example, Hattne et al (2014) and Kirian et al (2011). We will discuss three types of scaling and provide references to more explicit descriptions where necessary

CONCEPTS
Inter-set scaling
The AASR method
The WLS method
Intra-data set scaling
EXAMPLE OF AN APPLICATION
Intra-data set scaling of set 3
CONCLUSIONS
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