Laser-Plasma Spectroscopy of Hydroxyl with Applications.

This article discusses laser-induced laboratory-air plasma measurements and analysis of hydroxyl (OH) ultraviolet spectra. The computations of the OH spectra utilize line strength data that were developed previously and that are now communicated for the first time. The line strengths have been utilized extensively in interpretation of recorded molecular emission spectra and have been well-tested in laser-induced fluorescence applications for the purpose of temperature inferences from recorded data.

The Plasma Spectroscopic Study of Dergaon Meteorite, India.

Meteorites are the recoverable portions of asteroids that reach the surface of the Earth. Meteorites are rare extraterrestrial objects studied extensively to improve our understanding of planetary evolution. In this work, we used calibration-free laser-induced breakdown spectroscopy (CF-LIBS) to evaluate the quantitative elemental and molecular analyses of the Dergaon meteorite, a H 4-5 chondrite fall sample from Assam, India.

Laser-Plasma Spatiotemporal Cyanide Spectroscopy and Applications.

This article reports new measurements of laser-induced plasma hypersonic expansion measurements of diatomic molecular cyanide (CN). Focused, high-peak-power 1064 nm Q-switched radiation of the order of 1 TW/cm 2 generated optical breakdown plasma in a cell containing a 1:1 molar gas mixture of N 2 and CO 2 at a fixed pressure of 1.1 × 10 5 Pascal and in a 100 mL/min flow of the mixture.

Mapping of Uranium in Surrogate Nuclear Debris Using Laser-Induced Breakdown Spectroscopy (LIBS).

This work describes the use of a laser-induced breakdown spectroscopy (LIBS) system to conduct macroscopic elemental mapping of uranium and iron on the exterior surface and interior center cross-section of surrogate nuclear debris for the first time. The results suggest that similar LIBS systems could be packaged for use as an effective instrument for screening samples during collection activities in the field or to conduct process control measurements during the production of debris surrogates. The technique focuses on the mitigation of chemical and physical matrix effects of four uranium atomic emission lines, relatively free of interferences and of good analytical value.

Emission spectroscopy of expanding laser-induced gaseous hydrogen-nitrogen plasma.

Microplasma is generated in an ultra-high-pure H and N gas mixture with a Nd:YAG laser device that is operated at the fundamental wavelength of 1064 nm. The gas mixture ratio of H and N is 9 to 1 at a pressure of 1.21 ± 0.

Laser-induced optical breakdown spectroscopy of polymer materials based on evaluation of molecular emission bands.

Laser-induced breakdown spectroscopy (LIBS) for composition analysis of polymer materials results in optical spectra containing atomic and ionic emission lines as well as molecular emission bands. In the present work, the molecular bands are analyzed to obtain spectroscopic information about the plasma state in an effort to quantify the content of different elements in the polymers. Polyethylene (PE) and a rubber material from tire production are investigated employing 157nmF laser and 532nm Nd:YAG laser ablation in nitrogen and argon gas background or in air.

Measurement of Strontium Monoxide in Methane-Air Flames.

The spectroscopy of alkaline earth metal compounds is stimulated by the use of these compounds in practical areas ranging from technology to medicine. Applications in the field of pyrotechnics were the motivation for a series of flame emission spectroscopy experiments with strontium-containing compounds. Specifically, strontium monoxide (SrO) was studied as a candidate radiator for the diagnosis of methane-air flames.

A fundamental understanding of the dependence of the laser-induced breakdown spectroscopy (LIBS) signal strength on the complex focusing dynamics of femtosecond laser pulses on either side of the focus.

We correlate the focusing dynamics of 50 femtosecond (fs) laser radiation as it interacts with a silicon sample to laser-induced breakdown spectroscopy (LIBS) signal strength. Presented are concentric ring-shaped variations in the electric field in the prefocus region due to lens aberrations and nonsymmetry between the prefocus and post-focus beam profile as a result of continuum generation, occurring around the focus. Experimental results show different signal trends for both atmospheric and vacuum conditions, attributed to the existence of a continuum for the former.

Laser-induced plasma spectroscopy of hydrogen Balmer series in laboratory air.

Stark-broadened emission profiles for the hydrogen alpha and beta Balmer series lines in plasma are measured to characterize electron density and temperature. Plasma is generated using a typical laser-induced breakdown spectroscopy (LIBS) arrangement that employs a focused Q-switched neodymium-doped yttrium aluminum garnet (Nd : YAG) laser, operating at the fundamental wavelength of 1064 nm. The temporal evolution of the hydrogen Balmer series lines is explored using LIBS.

Aluminum monoxide emission measurements in a laser-induced plasma.

We report temperature inferences from time-resolved emission spectra of a micro-sized plasma following laser ablation of an aluminum sample. The laser-induced breakdown event is created with the use of nanosecond pulsed laser radiation. Plasma temperatures are inferred from the aluminum monoxide spectroscopic emissions of the aluminum sample by fitting experimental to theoretically calculated spectra with a nonlinear fitting algorithm.

Carbon swan spectra measurements following breakdown of nitro compound explosive simulants.

Our measurements of micro-plasma following laser-induced optical breakdown of nitro compound explosive simulants, here 3-nitrobenzoic acid, show well-developed molecular spectra during the first several hundreds of nanoseconds. Analysis of recorded carbon spectra is accomplished using accurate line strengths for the diatomic molecular Swan system. Presence of hydrogen-beta allows us to infer electron density in the plasma evolution.

Aluminum flame temperature measurements in solid propellant combustion.

The temperature in an aluminized propellant is determined as a function of height and plume depth from diatomic AlO and thermal emission spectra. Higher in the plume, 305 and 508 mm from the burning surface, measured AlO emission spectra show an average temperature with 1σ errors of 2980 ± 80 K. Lower in the plume, 152 mm from the burning surface, an average AlO emission temperature of 2450 ± 100 K is inferred.

Measurement and analysis of atomic hydrogen and diatomic molecular AlO, C2, CN, and TiO spectra following laser-induced optical breakdown.

In this work, we present time-resolved measurements of atomic and diatomic spectra following laser-induced optical breakdown. A typical LIBS arrangement is used. Here we operate a Nd:YAG laser at a frequency of 10 Hz at the fundamental wavelength of 1,064 nm.

Optical diagnostic and therapy applications of femtosecond laser radiation using lens-axicon focusing.

Diagnostic modalities by means of optical and/or near infrared femtosecond radiation through biological media can in principle be adapted to therapeutic applications. Of specific interest are soft tissue diagnostics and subsequent therapy through hard tissue such as bone. Femto-second laser pulses are delivered to hydroxyapatite representing bone, and photo-acoustic spectroscopy is presented in order to identify the location of optical anomalies in an otherwise homogeneous medium.

Measurement and analysis of titanium monoxide spectra in laser-induced plasma.

We present results including measurement and analysis of titanium monoxide. Pulsed, nanosecond Nd:YAG laser radiation is used in a typical laser-induced breakdown spectroscopy arrangement to record the spectra. This scheme provides experiments analogous to pulsed laser deposition tactics and allows for time-resolved spectroscopic analysis.

Analysis of time-resolved superposed atomic hydrogen Balmer lines and molecular diatomic carbon spectra.

We present analysis of superposition spectra following laser-induced breakdown (LIB) of methane. Both hydrogen-beta and hydrogen-gamma lines contain discernible contributions from diatomic carbon emissions for time delays of 1 to 2 μs from pulsed, 8 ns, infrared Nd:YAG laser radiation LIB. Analysis of the atomic lines and molecular C(2) spectra reveal electron and molecular excitation temperatures of typically 13,000 and 5000 K, respectively.

Computation of AlO B2Σ+ → X2Σ+ emission spectra.

Application of molecular spectroscopy to analytical chemistry usually requires accurate description of the particular transition of interest. In this communication we describe the creation of a list of spectral lines. Following the introduction and definition of the line strength, we present a recipe for computation of diatomic-line-strengths, including the Hönl-London factor and electric dipole line strength for each spectral line.

Time-resolved spectroscopy measurements of hydrogen-alpha, -beta, and -gamma emissions.

Hydrogen emission spectroscopy results are reported following laser-induced optical breakdown with infrared Nd:YAG laser radiation focused into a pulsed methane flow. Measurements of Stark-broadened atomic hydrogen-alpha, -beta, and -gamma lines show electron number densities of 0.3 to 4x10(17) cm(-3) for time delays of 2.

Temperature distribution in dental tissue after interaction with femtosecond laser pulses.

Algebraic and numerical solutions are presented of the temperature rise in dental tissue due to interaction with ultrashort optical radiation. Results of the studies with femtosecond laser pulses show agreement between theory and experiment. A temperature rise of typically 5 K is found for a 40 millisecond train of 7 nJ, 70 fs laser pulses at a repetition rate of 80 MHz.

Spontaneous emission from the C3 radical in carbon plasma.

Spontaneous emission measurements are discussed for the Swings transitions of the C(3) radical in laser-generated graphite plasma, and the spectroscopy of the C(3) radical in carbon vapor and plasma is summarized. A review is given of some theoretical calculations and emission spectroscopic investigations are presented. Time-averaged, laser-induced optical breakdown spectra are reported from Nd:YAG laser generated graphite microplasma.

Measurements of aluminum and hydrogen microplasma.

We report time-averaged and time-resolved emission spectra subsequent to laser-induced optical breakdown of aluminum in laboratory air and in hydrogen gas. The microplasma generated by nominal 10 ns IR laser radiation shows Stark-broadened and shifted atomic lines. An analysis of the H(alpha) and H(beta) Balmer series lines and selected aluminum lines allows one to determine electron number density in the range of 0.

Diatomic Hönl-London factor computer program.

A new method is presented for computation of diatomic rotational line strengths, or Hönl-London factors. The traditional approach includes separately calculating line positions and Hönl-London factors and assigning parity labels. The present approach shows that one merely computes the line strength for all possible term differences and discards those differences for which the strength vanishes.

Laser-induced carbon plasma emission spectroscopic measurements on solid targets and in gas-phase optical breakdown.

We report measurements of time- and spatially averaged spontaneous-emission spectra following laser-induced breakdown on a solid graphite/ambient gas interface and on solid graphite in vacuum, and also emission spectra from gas-phase optical breakdown in allene C3H4 and helium, and in CO2 and helium mixtures. These emission spectra were dominated by CII (singly ionized carbon), CIII (doubly ionized carbon), hydrogen Balmer beta (Hbeta), and Swan C2 band features. Using the local thermodynamic equilibrium and thin plasma assumptions, we derived electron number density and electron temperature estimates.

Measurement and analysis of atomic and diatomic carbon spectra from laser ablation of graphite.

Spectra from plasma produced by laser-induced breakdown of graphite were recorded and analyzed to increase our understanding of the way in which carbon nanoparticles are created during Nd:YAG laser ablation of graphite. The effects of various buffer gases were studied. Electron density and temperature were determined from spectra of the first and second ions of atomic carbon.