Laser-Pulse-Length Effects in Ultrafast Laser Desorption

Area of Science:

• Analytical Chemistry
• Physical Chemistry
• Spectroscopy

Background:

• Laser desorption (LD) is crucial for mass spectrometry (MS) sampling and ionization.
• Optimizing laser pulse length is key for efficient and gentle molecule desorption, impacting MS analysis costs and complexity.
• Previous studies lack systematic investigation into the optimal laser pulse length for LD in MS.

Purpose of the Study:

• To systematically investigate the effect of laser pulse length on molecule desorption efficiency and fragmentation.
• To determine the optimal pulse duration for laser desorption (LD) in mass spectrometry (MS) applications.
• To evaluate the potential of ultrashort laser pulses for trace analysis using LD-MS.

Main Methods:

• Direct comparison of femtosecond, picosecond, and nanosecond laser pulses for LD.
• Experiments conducted in vacuum to isolate LD effects, excluding collisional cooling and postionization interference.
• Resonance-enhanced multiphoton ionization used as the postionization technique.
• Analysis of over-the-counter medicaments (naproxen, ibuprofen) from tablets and aerosols (retene, ship emission) from quartz filters.

Main Results:

• Picosecond pulses showed benefits in reducing LD-induced fragmentation compared to nanosecond pulses.
• Desorption efficiency continuously increased as laser pulse length decreased.
• Ultrashort laser pulses (femtosecond and picosecond) demonstrate significant potential for trace analytics.

Conclusions:

• Decreasing laser pulse length, especially to femtosecond and picosecond regimes, enhances LD efficiency for MS.
• Ultrashort laser pulses offer a promising approach for sensitive trace molecule analysis via LD-MS.
• The findings are transferable to other LD-based analytical techniques due to controlled experimental conditions.