A Linear Ion Trap with an Expanded Inscribed Diameter to Improve Optical Access for Fluorescence Spectroscopy

Area of Science:

• Physical Chemistry
• Spectroscopy
• Ion Trapping Technology

Background:

• Fluorescence spectroscopy is crucial for studying molecular properties.
• Gas-phase ion spectroscopy is limited by optical access and sensitivity.
• Understanding chromophore microenvironments requires advanced spectroscopic tools.

Purpose of the Study:

• To design and implement a custom linear ion trap for enhanced fluorescence spectroscopy of gas-phase ions.
• To enable spectroscopic studies at cryogenic temperatures (below 25 K).
• To investigate excited state charge transfer processes influenced by the ion's microenvironment.

Main Methods:

• A custom-geometry linear ion trap with increased optical access (80% rod diameter).
• Integration with a closed-cycle helium refrigerator for cryogenic operation.
• Laser-induced fluorescence collection orthogonal to the excitation laser axis.

Main Results:

• Achieved high photon detection rates (10^7 photons/s) from trapped rhodamine 6G ions.
• Demonstrated temperature control below 25 K on the trap electrodes.
• The custom geometry significantly improved optical access to the ion cloud.

Conclusions:

• The developed linear ion trap facilitates sensitive fluorescence spectroscopy of gas-phase ions.
• This instrument expands the applicability of fluorescence spectroscopy to systems with low photon emission quantum yields.
• Enables detailed studies of microenvironment effects on excited-state dynamics in gas-phase ions.