Insight into Desorption Mechanisms in a Helium Low-Temperature Plasma Ionization Source Using Computational...

Area of Science:

• Analytical Chemistry
• Plasma Physics
• Surface Science

Background:

• Direct sampling and ionization of condensed-phase samples require understanding desorption mechanisms.
• Low-temperature plasma (LTP) is a key technique for ambient desorption/ionization mass spectrometry (MS).
• Fundamental desorption mechanisms in LTP and similar plasma sources are not fully understood.

Purpose of the Study:

• To investigate analyte desorption mechanisms from solid samples using plasma simulations.
• To elucidate the role of plasma-induced surface charge and electric fields in desorption.
• To identify key plasma parameters influencing desorption efficiency.

Main Methods:

• Utilized COMSOL Multiphysics for plasma simulations.
• Modeled a simplified helium LTP configuration exposing solid samples on glass.
• Analyzed surface charge accumulation and resulting electric fields.

Main Results:

• Plasma exposure leads to surface charge accumulation on the sample-substrate.
• Localized electric fields generated by surface charge likely disrupt analyte-substrate interactions, facilitating desorption.
• Simulated electron energies of approximately 2.5 eV were estimated as an indicator for desorption efficiency.

Conclusions:

• Plasma-induced surface charge and electric fields play a crucial role in analyte desorption.
• The findings offer new insights into the interplay between plasma phenomena and desorption processes.
• This research aids in optimizing analytical techniques relying on plasma-based desorption/ionization.