Strong-field ionization of sputtered molecules for biomolecular imaging

Area of Science:

• Physical Chemistry
• Surface Science
• Laser Physics

Background:

• Molecular thin films are crucial in various scientific applications.
• Photoionization is a key technique for analyzing molecular species.
• Laser-induced fragmentation can complicate analysis.

Purpose of the Study:

• To investigate the effect of laser wavelength on photoionization of sputtered molecules.
• To understand the underlying photoionization mechanisms.
• To optimize conditions for reduced fragmentation in mass spectrometry and bioimaging.

Main Methods:

• Sputtering molecules from thin films.
• Using high-field 125 fs mid-infrared laser pulses.
• Varying the photoionization wavelength.
• Analyzing photoionization spectra and fragmentation patterns.

Main Results:

• Increasing photoionization wavelength significantly reduces molecular fragmentation.
• The photoionization mechanism transitions from multi-electron excitation to tunnel ionization with increasing wavelength.
• Wavelength-dependent spectral analysis confirms the mechanism shift.

Conclusions:

• Mid-infrared photoionization offers a tunable pathway to control molecular fragmentation.
• Understanding the wavelength-dependent ionization mechanism is critical for applications.
• This research has implications for improving focused ion beam and mass spectrometry-based bioimaging.