X-ray multi-probe data acquisition: A novel technique for laser pump x-ray transient absorption spectroscopy

Area of Science:

• Spectroscopy
• Physical Chemistry
• Materials Science

Background:

• Synchrotron-based laser pump X-ray Transient Absorption (XTA) spectroscopy is crucial for studying ultrafast photophysical and photochemical processes.
• Existing data acquisition techniques face limitations in efficiently capturing time-resolved XTA signals across diverse experimental conditions.

Purpose of the Study:

• To develop and implement a novel data acquisition technique, X-ray Multi-Probe DAQ (XMP DAQ), for synchrotron-based XTA spectroscopy.
• To enable efficient and simultaneous measurement of time-resolved XTA spectra across a wide range of pump-probe time delays.

Main Methods:

• Developed XMP DAQ utilizing high-performance analog-to-digital converters and custom software.
• Implemented two distinct XMP DAQ schemes: Current Integration (CI) DAQ for high count rates and Photon Counting (PC) DAQ for low count rates and closely spaced X-ray pulses.
• CI DAQ employs a fitting procedure to extract time-resolved absorption intensity, enhancing accuracy by mitigating baseline drifts.

Main Results:

• XMP DAQ generates a two-dimensional XTA dataset, capturing spectra at thousands of pump-probe time delays simultaneously.
• CI DAQ effectively measures XTA data with widely spaced X-ray pulses and high count rates.
• PC DAQ is optimized for closely spaced X-ray pulses and low count rates, providing accurate spectral calculations via time-resolved histograms.

Conclusions:

• XMP DAQ significantly advances XTA spectroscopy by enabling efficient, quantitative analysis of photophysical and photochemical processes.
• The technique provides comprehensive time-resolved data from sub-nanosecond to microsecond timescales and beyond.
• The dual CI and PC DAQ schemes offer versatile solutions for various synchrotron operating modes and experimental needs.