Subcategory: Physics (not Nanoscience)
Keith A. Tukes Jr. - Hampton University
Co-Author(s): Uwe Hommerich and Eiei Brown, Hampton University, Hampton, VA
Laser-Induced breakdown spectroscopy (LIBS) is a method of chemical identification which requires very little sample preparation and is widely applicable . Particularly, LIBS has shown to hold great promise for remote sensing of explosive materials. LIBS is the process of creating and analyzing the atomic and molecular emission spectra that are generated by focusing a pulsed laser beam onto the surface of a sample, creating a plasma spark at the surface, collecting that emitted light ,and directing it to a detector. One can identify the elemental and molecular composition of the sample by comparing LIBS emission signatures with the NIST atomic spectra database and FTIR spectra, respectively. In this research, comparative LIBS studies were performed on copper and potassium containing samples under pulsed laser excitation at 1.064 µm and 1.57 µm (eye-safe). The study was focused on identifying and comparing atomic and molecular emission lines as well as determining the plasma temperature for different laser wavelengths. The Boltzmann distribution of atomic energy states is dependent upon the temperature of the constituents of the system, assuming that all constituents have the same temperature. Therefore the laser-induced plasma must be in local thermodynamic equilibrium (LTE) and the plasma temperature is calculated using the relative intensities of the same atomic/ionic species’ emissions, the upper level energies and degeneracies, and the transition strengths [2-3]. Experimental details, spectroscopic results, and temperature modeling of visible and infrared LIBS emission spectra for copper and potassium compounds will be discussed at the conference. Future endeavors will include calculation of the electron density for use with the NIST atomic spectra database to examine the resemblance of the LIBS spectra to the NIST-predicted Saha-LTE spectra.
Funder Acknowledgement(s): Army Research Office; CREST Center for Laser Science; National Science Foundation
Faculty Advisor: Uwe Hommerich, firstname.lastname@example.org
Role: I researched the 'Boltzmann-Method' to understand how the plasma temperature can be extracted from the LIBS spectra. I ran the LIBS experiment, aligning the 1064 nm Q-Switched Nd:YAG laser, lenses and detectors. I prepared the bulk-pellet samples and created copper-containing penny samples. Created LIBS spectral-graphs and Boltzmann plots from which I extracted the plasma temperatures.