A stop-flow sample delivery system for transient spectroscopy

Area of Science:

• Spectroscopy
• Chemical Physics
• Physical Chemistry

Background:

• Transient spectroscopy requires precise sample delivery for analyzing rapid molecular processes.
• Existing methods may be sample-intensive or lack the temporal resolution needed for certain laser systems.

Purpose of the Study:

• To develop and demonstrate a highly sample-efficient stop-flow system for transient spectroscopy.
• To adapt the system for laser-based instruments with moderate repetition rates (10-100 Hz).

Main Methods:

• Integration of two pulsing micro-valves within a flow cuvette for transient IR spectroscopy.
• A peristaltic pump drives the flow cycle, enabling precise sample manipulation.
• Utilizing laser-based instruments, including quantum-cascade lasers and amplified femtosecond lasers.

Main Results:

• The system effectively stops sample flow for analysis and rapidly delivers new samples within 1 ms.
• Demonstrated performance using transient IR spectroscopy of azobenzene derivative photoisomerization.
• Achieved high sample efficiency, requiring only small volumes while exciting a large molecular fraction.

Conclusions:

• The developed stop-flow system offers a significant advancement in sample delivery for transient spectroscopy.
• Its efficiency and compatibility with laser-based instruments make it valuable for studying fast chemical dynamics.
• Enables detailed investigation of molecular photoisomerization with minimal sample consumption.