What is Laser Induced Breakdown Spectroscopy (LIBS)?

Laser Induced Breakdown Spectroscopy—abbreviated as LIBS—is an analytical technique that has been used in laboratories for several years. The majority of handheld LIBS analyzers are used for quick sorting of alloys in scrap yards, and identification and analysis of alloys in a wide range of applications within the metals industry.

How Does LIBS Work?

During LIBS analysis, a focused pulsed laser bombards the sample removing a tiny amount of material from the surface. Similarly, during a typical one-second measurement, the sample is struck by thousands of pulses which heat up the material up to and over 10,000 °C. The temperature is so high that the atoms in fact break up and form a plasma.

In spite of these high temperatures, the sample does not become too hot to the touch during analysis, and hence it can be held safely by hand during measurement.

What is Happening Within the Atoms?

When the high power pulsed laser strikes the sample, the electrons in the outer shells of the outer atoms are ejected. Since electrons in the outer shells are shielded by the electrons in the inner shell, they are not strongly pulled by the nucleus. This implies that less energy is required to eject electrons from the outer shells.

A vacancy is created by the ejected electrons, rendering the atom unstable. When the pulse stops, the plasma begins to cool down and the vacancy is occupied by electrons cascading down from the outer shells of the electrons. The excess energy released when the electrons move between two shells or energy levels is emitted in the form of element-specific light.

For a typical metallic sample containing manganese, iron, nickel, vanadium, chromium, and so on, each element emits several wavelengths resulting in a spectrum of up to thousands of peaks. A fiber optic cable is used to collect the wavelengths of light, which are subsequently processed by the spectrometer.

A specific spectral peak is associated with each element. LIBS spectra are fairly complex with potentially hundreds or even thousands of lines for one element.

The intensity of the spectrum peak is used to calculate the element concentration. Then, using an advanced algorithm, the sample type is identified and the concentrations are calculated.

Why do People Choose the Handheld LIBS Technique?

Currently, LIBS analyzer is one of the fastest analytical technologies available to identify and analyze metal alloys. It takes just a second to measure almost any alloy including aluminum alloys — making it up to 20 times faster than handheld XRF.

A LIBS analyzer is extremely robust as the detector is generally protected by sapphire glass, one of the hardest materials known at present. Therefore, it is possible to safely measure sharp and pointy objects, such as shavings and turnings.

It is also user-friendly. One just needs to point, shoot, and read the result from the screen.

The LIBS technique is almost entirely non-destructive. A LIBS analysis leaves a tiny burn spot which is so small that it is barely visible to the naked eye.

From a regulatory and licensing perspective, much less user intervention is required than for XRF. Generally, lengthy training classes or expensive licenses are not required. However, it is essential to check the local legislation regarding issues such as the use of safety goggles. It is highly recommended to use safety goggles when operating a Class 3B laser device.

Being an excellent alloy identification tool, LIBS can also deliver a good chemistry when needed.

This information has been sourced, reviewed and adapted from materials provided by Hitachi High-Tech Analytical Science.

For more information on this source, please visit Hitachi High-Tech Analytical Science.

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