Laser-Induced Breakdown Spectroscopy (LIBS) is an extremely powerful and flexible elemental analysis technique that utilizes the energy in a short, intense laser pulse to vaporize or “ablate” a small volume of sample material.  The ablated target material (whether solid, liquid, or gas) absorbs enough energy to vaporize and then ionize the constituent atoms, creating a small cloud of plasma (free ions and electrons) that expands rapidly.  As the cloud expands and cools, a significant fraction of the ions recombine to form excited atoms, which eventually decay via spontaneous emission to the atomic ground state (the state of lowest energy in the atom).  The photons given off during spontaneous emission can be collected and spectrally analyzed which provides a “spectral fingerprint” of all the constituent elements of the target and the plasma.  Since each element has a unique spectral fingerprint, relative and absolute elemental concentrations within the target material can be determined.  Theoretically, this measurement can be accomplished with one laser pulse (about 10 ns), resulting in a very rapid analysis of the target (total measurement time less than one second).  Because the target material is interrogated by a laser beam and the plasma is analyzed by “all–optical” techniques, the analysis can be performed remotely or on hazardous materials.

                               

Our Research

Our research is targeted toward two areas: the biomedical applications of LIBS-based technologies and the use of pulsed laser sources in laboratory astrophysics measurements (these are fundamental atomic physics measurements on ionic species of interest to observational astronomers.)  To read more about the new Wayne State University Biomedical Physics major through the Dept. of Physics and Astronomy, click here.  To read more about our Department of Physics and Astronomy, click here.


To date, most of the experiments have focused on exploiting the advantages of LIBS, and these projects are detailed below.  Projects with a biomedical thrust are marked with a DNA strand symbol.

Active Specific Research Projects (Summer/Fall 2008)

1) LIBS as a tool to detect and identify bacteria.  The BIOMAS Project: Bacterial Identification by Optical, Molecular, and Atomic Spectroscopy. (Prof. Rehse/Jonathan Diedrich /Narmatha Jeyasingham/Qassem Mohaidat/Khozima Hamasha).   In just the last three years, it has been determined that LIBS can be utilized to discriminate between bacterial strains on the basis of the atomic spectrum alone.  This summer will see initial investigations into the ability to discriminate between two very common non-pathogenic bacteria strains: Escherichia coli and Pseudomonas aeruginosa.  Eventually, we wish to apply the technique as a clinical diagnostic tool for the identification of such dangerous pathogens as Vibrio cholerae (which causes cholera) and EHEC which causes kidney damage in children.

4) LIBS will be used to determine the relative concentrations of Fe in magnetic nanoparticle samples (Emmett Brown).  Iron oxide nanoparticles are prepared in a bio-compatible alginate matrix by another research group in our department (Lawes).  This bio-compatible matrix can be introduced into the human body and it is hoped that the magnetic nanoparticles will provide unique behavior of medicinal value.  These samples are prepared in a chemical process, with the percent concentration of iron being completely unknown.  It is our intention to use LIBS to measure the fractional percentage of iron in these samples, yielding a quick and inexpensive assay of the material.

5) We are testing the ability of LIBS to detect trace concentrations of aluminum in a simulated tissue matrix (Marian Adamson).  This project has relevance to the Wayne State University Smart Sensors and Integrated Microsystems neurological implant program.  It is believed that aluminum atoms can diffuse out of a sapphire matrix into human tissue in which an integrated-circuit implant has been placed.  This diffusion of aluminum out of what is supposed to be an "inert" substrate is bad for the subject and the implant.  We are trying to determine whether LIBS can be used as a sensitive probe to detect this process.  Initial investigations will begin by identifying suitable tissue "simulants" which can be used to safely test the technique.  We will then try to determine what the limit of detection (LOD) is for Al in such systems.  Lastly, we will explore the delivery of the laser and collection of the light via a single optical fiber to simulate actual in vivo use of the technique.

6) Molecular evolution in laser-created plasmas at the air/water interface (Arathi Padmanabhan).  We are currently studying the temporal evolution and power dependence of various molecular species in our LIBS plasmas created by ablating the surface of water.  The molecules, which result from combination of liberated atoms in the plasma, emit detectable light to well after 40 microseconds after the laser pulse - whereas the emission from atomic species is gone after nearly 5 microseconds.  We are also investigating the effect of using different "bath gases" on this behavior by performing our ablation in argon, nitrogen, and helium.

Recent Research Papers

18. R. Li, R. Chatelain, R.A. Holt, S.J. Rehse, S.D. Rosner, and T.J. Scholl, “Oscillator strength measurements in Pr II with the fast-ion-beam laser-induced-fluorescence technique,” Physica Scripta 76, 577-592 (2007).

9. Broadband Precision Wavelength Meter Based on a Stepping Fabry-Perot Interferometer, T.J. Scholl, S.J. Rehse, R.A. Holt, and S.D. Rosner, Rev. Sci. Inst. 75, 3318 (2004)

8.  Laser Collimation of an Atomic Gallium Beam, S.J. Rehse, K.M. Bockel, and S.A. Lee, Phys. Rev. A 69, 063404 (2004)

7. Steven J. Rehse, Light Force Manipulation of Gallium Atoms, Dissertation (Ph.D.), Colorado State University, 2002

6. Generation of 125 mW Frequency Stabilized Continuous-wave Tunable Laser Light at 295 nm by Frequency Doubling in a BBO Crystal, S.J. Rehse and S.A. Lee, Opt. Comm. 213, 347 (2002)

5. Light force manipulation of an atomic gallium beam, S.J. Rehse, K. Bockel, and S.A. Lee, in Technical Digest. Summaries of papers presented at the Quantum Electronics and Laser Science Conference, 218, (IEEE 2001)

4. Measurement of the Hyperfine Structure of the 4d2D3/2,5/2 Levels and Isotope Shifts of the 4p2P3/2 - 4d2D3/2 and 4p2P3/2 - 4d2D5/2 Transitions in Gallium 69 and 71, S.J. Rehse, W.M. Fairbank Jr., and S.A. Lee, JOSA B 18, 1 (2001)

3. Optical Manipulation of Group III Atoms, S.J. Rehse, R.W. McGowan and S.A. Lee, Appl. Phys. B 70, 657 (2000)

2. Light force manipulation of group III atoms, S.J. Rehse and S.A. Lee, in Laser Spectroscopy. 14th International Conference. ICOLS99, 316, 1999

1. Nanolithography With Metastable Neon Atoms: Enhanced Rate of Contamination Resist Formation for Nanostructure Fabrication, S.J. Rehse, A. D. Glueck, S.A. Lee, A.B. Goulakov, C.S. Menoni, D.C. Ralph, K.S. Johnson and M. Prentiss, Appl. Phys. Lett. 71, 1427, (1997)

Last updated on 12/02/08