Abstract
The detailed pathways of photoactivity on ultrafast time scales are a topic of contemporary interest. Using a tabletop apparatus based on a laser plasma X-ray source and an array of cryogenic microcalorimeter X-ray detectors, we measured a transient X-ray absorption spectrum during the ferrioxalate photoreduction reaction. With these high-efficiency detectors, we observe the Fe K edge move to lower energies and the amplitude of the extended X-ray absorption fine structure reduce, consistent with a photoreduction mechanism in which electron transfer precedes disassociation. These results are compared to previously published transient X-ray absorption measurements on the same reaction and found to be consistent with the results from Ogi et al. and inconsistent with the results of Chen et al. (Ogi, Y.; et al. Struct. Dyn. 2015, 2, 034901; Chen, J.; Zhang, H.; Tomov, I. V.; Ding, X.; Rentzepis, P. M. Chem. Phys. Lett. 2007, 437, 50-55). We provide quantitative limits on the Fe-O bond length change. Finally, we review potential improvements to our measurement technique, highlighting the future potential of tabletop X-ray science using microcalorimeter sensors.
| Original language | English |
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| Pages (from-to) | 1099-1104 |
| Number of pages | 6 |
| Journal | Journal of Physical Chemistry Letters |
| Volume | 8 |
| Issue number | 5 |
| DOIs | |
| State | Published - Mar 2 2017 |
Funding
The authors thank Eleanor Waxman for useful discussions and Ilari Maasilta and his group at Jyväskylä University (Finland) for their international participation in the connection of microcalorimeter sensors to tabletop time-resolved X-ray science. The authors gratefully acknowledge financial support from the NIST Innovations in Measurement Science program and U.S. Department of Energy, Basic Energy Sciences. Sector 20 facilities at the Advanced Photon Source are supported by the U.S. Department of Energy, Basic Energy Sciences and the Canadian Light Source.