Effects of Laser Beam Focusing Characteristics on Laser-Induced Breakdown Spectra.

Area of Science:

• Analytical Chemistry
• Planetary Science
• Spectroscopy

Background:

• Laser-induced breakdown spectroscopy (LIBS) is a powerful analytical technique.
• Understanding optimal experimental parameters is crucial for accurate elemental analysis.
• LIBS is a potential tool for in-situ analysis on planetary missions.

Purpose of the Study:

• To investigate the effect of laser focusing conditions on LIBS.
• To compare results in Earth and simulated Martian atmospheres.
• To determine optimal focal conditions for atomic and ionic emission detection.

Main Methods:

• Experiments varied lens-to-sample distance to alter focal spot size.
• LIBS was performed on aluminum, copper, and steel samples.
• Atomic and ionic emission lines were monitored.

Main Results:

• Atomic and ionic emission intensities showed distinct peak distributions with varying focal distances.
• In Earth's atmosphere, ionic emissions peaked with surface focus, while atomic emissions peaked deeper within the sample.
• In simulated Martian atmospheres, atomic emissions peaked with surface focus, and ionic emissions peaked near the surface.

Conclusions:

• Laser focusing conditions critically influence LIBS spectral line intensities.
• Optimal focusing strategies differ for atomic versus ionic species.
• Atmospheric conditions (Earth vs. Mars) alter the optimal laser focus for LIBS analysis.