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. Moreover, new experiments with Q-switched laser pulses illustrate occurrence of molecular recombination spectra for time delays of the order of several dozen of microseconds after plasma initiation. The OH signals occur due to the natural humidity in laboratory air. Centrifugal stretching of the Franck-Condon factors and r-centroids are included in the process of determining the line strengths that are communicated as a Supplementary File. Laser spectroscopy applications of detailed OH computations include laser-induced plasma and combustion analyses, to name but two applications. This work also includes literature references that address various diagnosis applications.

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. Line-of-sight (LOS) analysis of recorded molecular spectra indicated the outgoing shockwave at expansion speeds well in excess of Mach 5. Spectra of atomic carbon confirmed increased electron density near the shockwave, and, equally, molecular CN spectra revealed higher excitation temperature near the shockwave. Results were consistent with corresponding high-speed shadowgraphs obtained by visualization with an effective shutter speed of 5 nanoseconds. In addition, LOS analysis and the application of integral inversion techniques allow inferences about the spatiotemporal plasma distribution.

Verification of Safety Compliance of Delivering Radionuclides at Vanderbilt University.

Various radionuclides are transported at Vanderbilt University and Vanderbilt University Medical Center on a daily basis, to provide the necessities for diagnostic, therapeutic, and research applications. The delivery of the radionuclides takes various pathways where the general public may receive radiation doses. The Tennessee Department of Environment and Health Radiological Division regulates the dose limits for members of the public to be less than 1 mSv per year and 20 µSv in any hour. We designed a project to verify that potential doses received by the general public meet state regulations. Before the departure of the delivery, dose rates from three directions at a distance of 30 cm with respect to the transport vehicle, were measured using a tissue equivalent survey meter. During the shipment, times were recorded and the number of persons encountered along the path was estimated. Annual and hourly doses were calculated, conservatively assuming that a member of general public would follow the shipment at a distance of 30 cm, for the entire duration of the delivery. Calculated dose rates for each delivery and various combinations of radionuclides were found to be below state regulation limits.

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

Microplasma is generated in an ultra-high-pure H2 and N2 gas mixture with a Nd:YAG laser device that is operated at the fundamental wavelength of 1064 nm. The gas mixture ratio of H2 and N2 is 9 to 1 at a pressure of 1.21 ± 0.03 105 Pa inside a chamber. A Czerny-Turner-type spectrometer and an intensified charge-coupled device are utilized for the recording of plasma emission spectra. The line-of-sight measurements are Abel inverted to determine the radial distributions of electron number density and temperature. Recently derived empirical formulas are utilized for the extraction of values for electron density. The Boltzmann plot and line-to-continuum methods are implemented for the diagnostic of electron excitation temperature. The expansion speed of the plasma kernel maximum electron temperature amounts to 1 km/s at a time delay of 300 ns. The microplasma, initiated by focusing 14 ns, 140 mJ pulses, can be described by an isentropic expansion model.