Date of Award


Document Type


Degree Name

Master of Science


Department of Engineering Physics

First Advisor

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.

AFIT Designator


DTIC Accession Number