Date of Award
Master of Science
Department of Engineering Physics
Paul J. Wolf, PhD
Ba, BaO, Sr and SrO were ablated by 248 nm laser pulses at fluences ranging from 270 mJ-/sq cm to 575 mJ-/sq cm in vacuum and in 25 mtorr atmospheres of N2, O2 and microwave-discharged O2. The spectral emissions of these plumes were compared for indications of ionization due to Ba or Sr collisions with each gas. The addition of a background gas increased the ion and neutral signature across the spectrum. SrO band emission was observed at 16,600-16,900/cm and possible BaO band emissions were observed in the 18,250-18,400/cm, 19,000-19700/cm and 19,800-20,000/cm regions. A screened plate ion probe was use to establish the ion content of the Ba plume. A time of flight study established low-pressure (1 to 35 mtorr) and low-fluence (40 to 160 mJ-/sq cm relationships on Ba(+) velocity and population. Observed ion velocities ranged from 3.1 km/sec. To 4.5 km/sec. Results indicate the addition of a background gas at pressures less than 25 mtorr quenches Ba(+) in the plume and retards the plume expansion.
DTIC Accession Number
Byers, David L., "Investigation of Ba, BaO, Sr and SrO Pulsed Laser-Induced Vapor Plumes in N2, O2, Microwave Discharged O2, and Vacuum at Low Laser Fluence" (1996). Theses and Dissertations. 5854.