Introduction to LIBS

Laser Spark Spectroscopy (LASS), Laser-Induced Plasma Spectroscopy (LIPS) or, as it is more often known, Laser-Induced Breakdown Spectroscopy (LIBS), is a form of atomic emission spectroscopy in which a pulsed laser is used as the excitation source.  The output beam of the laser is focussed to a small spot on the surface of the sample being analysed so as to generate a short-lived, luminous plasma, the optical emissions of which may be detected by a suitable optical spectrograph.  The recorded spectrum may then be used to yield information on the elemental composition of the sample.  A key attribute of LIBS is that only optical access to the sample is required, which allows LIBS to be used for remote, non-contact analysis of materials which may be hazardous or otherwise difficult to handle (e.g. high temperature, radioactive, etc).  LIBS can also offer very rapid measurements, allowing analysis of, for example, fast moving materials on a conveyor belt during waste sorting and recycling.
 
The development of LIBS can be traced back to the work of Frederick Brech and Lee Cross during 1962 when they reported the observation of emission spectra from a metal target using a ruby maser.¹  The use of a pulsed laser to produce a luminous plasma for the purpose of spectrochemical analysis of a material was first reported in 1963 by a research group at the Ford Motor Company (Dearburn, Michigan, USA) who used a “giant pulse”, Q-switched ruby laser.²  A few years later, members of this research group applied the same experimental technique to molten stainless-steel samples, producing calibration curves for nickel and chromium that were found to be very similar to those obtained using solid samples.³  This clearly demonstrated the potential of LIBS for remote characterisation of hazardous materials although at that time the lack of suitable lasers and optical detectors hampered the development of this new technique.  Over the next two decades, advances in laser technology were such that real-world applications could be considered more seriously, but it was not until the 1980s that detector technology had advanced sufficiently to allow LIBS to become more than just a scientific curiosity.  The availability of time-gated CCD array detectors made a major impact on the development of LIBS as they were found to be particularly useful for recording the transient emission spectra from laser-induced plasma.  Many of the current manifestations of LIBS originate from work dating back to the early 1980s by Leon Radziemski, David Cremers and co-workers at Los Alamos National Laboratory (New Mexico, USA), and it was from this group that the acronym LIBS first appeared.

References
  1. F. Brech and L. Cross, Appl. Spectrosc. 16, 59 (1962).
  2. P.D. Maker, R.W. Terhune and C.M. Savage, “Optical third harmonic generation”, 3rd Internat. Conf. on Quant. Electron., Paris, France (1963).
  3. E.F. Runge, S. Bonfiglio and F.R. Bryan, Spectrochim. Acta 22, 1678–1680 (1966).