WHAT IT IS
The excimer 193 nm laser ablation system is a gas-based ultraviolet laser source widely used in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Excimer lasers employ a mixture of rare gas and halogen (commonly ArF) to generate pulses at 193 nm. This deep-UV wavelength is absorbed efficiently by most solid materials, enabling stoichiometric ablation with reduced thermal effects and elemental fractionation. Excimer 193 nm lasers are considered the gold standard in high-precision elemental and isotopic analysis, particularly in geosciences, materials research, and environmental studies.
HOW IT WORKS
Laser Generation - An excimer medium (argon fluoride, ArF) is electrically excited, producing pulsed emission at 193 nm. Unlike solid-state lasers, excimer sources operate as gas-discharge systems.
Beam Delivery - Optical components guide and shape the 193 nm beam into the ablation cell. Spot sizes typically range from 1–100 µm, allowing both microanalysis and mapping.
Sample Interaction - The deep-UV photons are strongly absorbed by nearly all materials, producing efficient material removal. Short wavelength minimizes heat transfer, leading to more stoichiometric particle release.
Aerosol Transport - Carrier gas (usually He with Ar addition) sweeps the ablated aerosol out of the cell and into the ICP. Fine particle size distribution supports efficient transport and ionization.
Detection - In the ICP, particles are atomized and ionized. The mass spectrometer detects ions, yielding elemental concentrations and isotopic ratios.
The 193 nm wavelength provides superior absorption compared with 213 or 266 nm lasers, improving reproducibility and reducing matrix effects.
ADVANTAGES
Efficient Ablation: High photon energy at 193 nm is absorbed by a wide variety of materials.
Low Fractionation: Reduced melting and elemental fractionation compared with longer wavelengths.
Versatile Resolution: Adjustable spot sizes support both micron-scale analysis and larger ablation areas.
High Reproducibility: Delivers consistent results across diverse samples, improving quantification.
Established Standard: Widely regarded as the reference laser type for geochemical and environmental LA-ICP-MS.
CHALLENGES AND LIMITATIONS
High Cost: Excimer systems are more expensive than solid-state Nd:YAG lasers.
Maintenance: Gas replacement, optical cleaning, and alignment increase service demands.
Size and Infrastructure: Larger footprint and need for exhaust systems compared with compact solid-state lasers.
Operational Complexity: Requires careful handling of gas mixtures and high-voltage discharges.
Competition from Femtosecond Lasers: Although excimers remain widely used, ultrafast femtosecond lasers offer even lower thermal effects in some applications.