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Quantitative Analysis of Vacuum Induction Melting by Laser-induced Breakdown Spectroscopy

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UV laser-induced desorption mechanism analyzed through two-layer alkali halide samples.

F A Fernández-Lima¹, C R Ponciano, E F da Silveira

¹Instituto Superior de Tecnologias y Ciencias Aplicadas, Havana, Cuba.

Journal of Mass Spectrometry : JMS

|December 21, 2007

Summary

UV laser ablation of alkali halide salts produces cluster ions. Their desorption yields suggest neutral components dominate, with two proposed mechanisms for ion ejection and recombination.

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Published on: February 14, 2014

Area of Science:

Materials Science
Physical Chemistry
Surface Science

Background:

Time-of-flight mass spectrometry (TOF-MS) is a key technique for analyzing ions.
Laser ablation is used to generate species from solid materials.
Alkali halide salts exhibit complex desorption behaviors under laser irradiation.

Purpose of the Study:

To investigate the desorption mechanisms of alkali halide salts using UV laser ablation.
To analyze the structure and formation of desorbed positive and negative cluster ions.
To understand the role of neutral species and layered structures in the desorption process.

Main Methods:

Time-of-flight mass spectrometry (TOF-MS) was employed.
UV laser ablation was used to desorb ions from alkali halide salts.
Experiments were conducted on homogeneously mixed and layered salt samples.

Main Results:

Observed cluster ions predominantly follow the structures (XY)(n)X(+) or (XY)(n)Y(-).
Desorption yields decreased exponentially with cluster size, indicating a dominant role for neutral components.
Analysis of mixed and layered salts revealed atomization of upper layers and colder ejection from deeper layers.

Conclusions:

The desorption of ionic salts by ns-pulsed lasers likely involves two sequential mechanisms.
These mechanisms include the ejection and recombination of ions in a hot plume.
The ejection of cold, preformed species from deeper or peripheral regions also contributes to the observed ions.