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Measuring energy-dependent photoelectron escape in microcrystals

Measuring energy-dependent photoelectron escape in microcrystals
Measuring energy-dependent photoelectron escape in microcrystals

With the increasing trend of using microcrystals and intense microbeams at synchrotron X-ray beamlines, radiation damage becomes a more pressing problem. Theoretical calculations show that the photoelectrons that primarily cause damage can escape microcrystals. This effect would become more pronounced with decreasing crystal size as well as at higher energies. To prove this effect, data from cryocooled lysozyme crystals of dimensions 5 × 3 × 3 and 20 × 8 × 8 µm mounted on cryo-transmission electron microscopy (cryo-TEM) grids were collected at 13.5 and 20.1 keV using a PILATUS CdTe 2M detector, which has a similar quantum efficiency at both energies. Accurate absorbed doses were calculated through the direct measurement of individual crystal sizes using scanning electron microscopy after the experiment and characterization of the X-ray microbeam. The crystal lifetime was then quantified based on the D1/2 metric. In this first systematic study, a longer crystal lifetime for smaller crystals was observed and crystal lifetime increased at higher X-ray energies, supporting the theoretical predictions of photoelectron escape. The use of detector technologies specifically optimized for data collection at energies above 20 keV allows the theoretically predicted photoelectron escape to be quantified and exploited, guiding future beamline-design choices.

CdTe detector, cryo-TEM sample mounts, microcrystals, photoelectron escape
2052-2525
129-135
Storm, Selina L S
e1281439-6351-406f-8880-41fa2b8a3d16
Crawshaw, Adam D
c3daa995-52e5-487b-a379-0638f43525fb
Devenish, Nicholas E
59d7608b-5d71-4c72-85de-758a2ccc3192
Bolton, Rachel
ef622c55-8cf1-46e0-b3dd-97c967dce111
Hall, David R
059b4bfd-1cfd-4931-836f-e86fb71f8bff
Tews, Ivo
9117fc5e-d01c-4f8d-a734-5b14d3eee8dd
Evans, Gwyndaf
46cb660a-bce7-4c62-8afc-de2a197ed02c
Storm, Selina L S
e1281439-6351-406f-8880-41fa2b8a3d16
Crawshaw, Adam D
c3daa995-52e5-487b-a379-0638f43525fb
Devenish, Nicholas E
59d7608b-5d71-4c72-85de-758a2ccc3192
Bolton, Rachel
ef622c55-8cf1-46e0-b3dd-97c967dce111
Hall, David R
059b4bfd-1cfd-4931-836f-e86fb71f8bff
Tews, Ivo
9117fc5e-d01c-4f8d-a734-5b14d3eee8dd
Evans, Gwyndaf
46cb660a-bce7-4c62-8afc-de2a197ed02c

Storm, Selina L S, Crawshaw, Adam D, Devenish, Nicholas E, Bolton, Rachel, Hall, David R, Tews, Ivo and Evans, Gwyndaf (2020) Measuring energy-dependent photoelectron escape in microcrystals. IUCrJ, 7 (Part 1), 129-135. (doi:10.1107/S2052252519016178).

Record type: Article

Abstract

With the increasing trend of using microcrystals and intense microbeams at synchrotron X-ray beamlines, radiation damage becomes a more pressing problem. Theoretical calculations show that the photoelectrons that primarily cause damage can escape microcrystals. This effect would become more pronounced with decreasing crystal size as well as at higher energies. To prove this effect, data from cryocooled lysozyme crystals of dimensions 5 × 3 × 3 and 20 × 8 × 8 µm mounted on cryo-transmission electron microscopy (cryo-TEM) grids were collected at 13.5 and 20.1 keV using a PILATUS CdTe 2M detector, which has a similar quantum efficiency at both energies. Accurate absorbed doses were calculated through the direct measurement of individual crystal sizes using scanning electron microscopy after the experiment and characterization of the X-ray microbeam. The crystal lifetime was then quantified based on the D1/2 metric. In this first systematic study, a longer crystal lifetime for smaller crystals was observed and crystal lifetime increased at higher X-ray energies, supporting the theoretical predictions of photoelectron escape. The use of detector technologies specifically optimized for data collection at energies above 20 keV allows the theoretically predicted photoelectron escape to be quantified and exploited, guiding future beamline-design choices.

Full text not available from this repository.

More information

Accepted/In Press date: 2 December 2019
Published date: 1 January 2020
Keywords: CdTe detector, cryo-TEM sample mounts, microcrystals, photoelectron escape

Identifiers

Local EPrints ID: 439284
URI: http://eprints.soton.ac.uk/id/eprint/439284
ISSN: 2052-2525
PURE UUID: 99ce5ef7-61b3-47c1-97fe-2ebc4f516d9a
ORCID for Ivo Tews: ORCID iD orcid.org/0000-0002-4704-1139

Catalogue record

Date deposited: 07 Apr 2020 16:36
Last modified: 18 Feb 2021 17:15

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