What is LIBS?

Laser-Induced Breakdown Spectroscopy (LIBS) is a spectroscopic technique using a laser-generated plasma to ablate and excite a sample, which can initially be in solid, liquid, or gaseous form.

Emission generated from the plasma is used to identify material constituents and can be used to identify, sort, and classify materials.

What can LIBS be used for?

LIBS can be used both in-process and in the laboratory for material identification. A very versatile method, it has the primary advantages of

  • Rapid analysis
  • Sensitive measurement of light elements like H, Li, C, and others
  • Little sample preparation
  • Sensitive to a wide variety of elements
  • Simultaneous reporting of elements

How does LIBS work?

Laser-Induced Breakdown Spectroscopy utilizes a focused pulse from a high peak-power laser to create a plasma in or on a solid, liquid, or gaseous media. Some of the energy in the plasma is used to ablate solid or liquid material (if present), and the plasma rapidly expands, sending a shock wave into the surrounding media. In the core of the plasma, effective temperatures can easily exceed 50,000 K or several eV. During this stage, material in the core of the plasma is vaporized and atomized, and the plasma is typically highly ionized.

Depending on conditions, but typically after 0.5 – 1 microsecond, the neutral states of the plasma typically reach local thermodynamic equilibrium. From this time onward, upper electronic states of atoms are thermally populated in Boltzmann equilibrium, such that the emission intensity of the atomic fluorescence I ~ exp(E/kT), where E is the upper state energy level of the fluorescing species.

As the plasma cools, continuum emission from the plasma (Bremstraalung emission) fades, typically much faster than emission lines from neutral and singly-ionized atomic lines, such that each elemental emission line has a particular optimum in a particular plasma. This optimum depends on the time / temperature history of the plasma, which in turn is dependent on the laser pulse energy and pulse length.

For typical 50 – 400 mJ, ~10 ns pulses, the sequence of events in the plasma is shown below; in higher-energy, longer-pulse plasmas, events are shifted to longer times, while for lower energy, shorter-pulse plasmas events are at shifted to shorter times