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Open AccessArticle

Bayesian Analysis of Femtosecond Pump-Probe Photoelectron-Photoion Coincidence Spectra with Fluctuating Laser Intensities

1
Institute of Experimental Physics, Graz University of Technology, 8010 Graz, Austria
2
Institute of Theoretical and Computational Physics, Graz University of Technology, 8010 Graz, Austria
*
Author to whom correspondence should be addressed.
Both authors contributed equally to this work.
Entropy 2019, 21(1), 93; https://doi.org/10.3390/e21010093
Received: 6 December 2018 / Revised: 10 January 2019 / Accepted: 16 January 2019 / Published: 19 January 2019
This paper employs Bayesian probability theory for analyzing data generated in femtosecond pump-probe photoelectron-photoion coincidence (PEPICO) experiments. These experiments allow investigating ultrafast dynamical processes in photoexcited molecules. Bayesian probability theory is consistently applied to data analysis problems occurring in these types of experiments such as background subtraction and false coincidences. We previously demonstrated that the Bayesian formalism has many advantages, amongst which are compensation of false coincidences, no overestimation of pump-only contributions, significantly increased signal-to-noise ratio, and applicability to any experimental situation and noise statistics. Most importantly, by accounting for false coincidences, our approach allows running experiments at higher ionization rates, resulting in an appreciable reduction of data acquisition times. In addition to our previous paper, we include fluctuating laser intensities, of which the straightforward implementation highlights yet another advantage of the Bayesian formalism. Our method is thoroughly scrutinized by challenging mock data, where we find a minor impact of laser fluctuations on false coincidences, yet a noteworthy influence on background subtraction. We apply our algorithm to data obtained in experiments and discuss the impact of laser fluctuations on the data analysis. View Full-Text
Keywords: photoelectron-photoion coincidence; PEPICO; femtosecond pump-probe spectroscopy; ultrafast molecular dynamics; Bayesian data analysis photoelectron-photoion coincidence; PEPICO; femtosecond pump-probe spectroscopy; ultrafast molecular dynamics; Bayesian data analysis
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    Link: https://github.com/fslab-tugraz/PEPICOBayes/
    Description: In the supplemantary material, we illustrate the necessity and principle of time-resolved photoelectron-photoion coincidence spectroscopy in two, hopefully easily understandable, simplifying animations. Also, in our github repostitory we make available our code, a manual including introductory examples and the data used in this paper.
MDPI and ACS Style

Heim, P.; Rumetshofer, M.; Ranftl, S.; Thaler, B.; Ernst, W.E.; Koch, M.; von der Linden, W. Bayesian Analysis of Femtosecond Pump-Probe Photoelectron-Photoion Coincidence Spectra with Fluctuating Laser Intensities. Entropy 2019, 21, 93.

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