Interaction of wide band gap single crystals with 248 nm excimer laser radiation. V. The role of photoelectronic processes in the formation of a fluorescent plume from MgO

Journal Article · Sat Feb 01 04:00:00 EST 1997 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.364183· OSTI ID:450242

Ermer, D R; Langford, S C; Dickinson, J T ^[1]

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1. Physics Department, Washington State University, Pullman, Washington 99164-2814 (United States)

We examine the formation of a fluorescent plume during pulsed laser irradiation of wide band gap materials at sub-band gap photon energies. We show that fluences near the threshold for plume fluorescence in MgO do not produce adequate electron densities for significant laser-plume interactions via inverse bremsstrahlung processes. At a wavelength of 248 nm, 30 ns pulse width, and fluences well below the onset of detected plume fluorescence, we observe intense Mg{sup +} emissions and electron temperatures in excess of 1 eV. The onset and growth of plume fluorescence closely parallels the neutral emission intensities, suggesting that the lack of plume fluorescence below the fluence threshold is due to the lack of gas phase neutral Mg. Time-resolved measurements of the atomic line emissions show peaks well {ital after} the peak laser intensity, arguing against direct laser-plume interactions. We propose that electron acceleration involves electrostatic interactions between photoelectrons and photoelectronically emitted ions. The unusual temporal evolution of the atomic line emissions can be attributed to the time dependence of the spatial overlap between neutral particles and the accelerated electrons that collisionally excite the atomic lines. {copyright} {ital 1997 American Institute of Physics.}

• DOE Contract Number: FG06-92ER14252
• OSTI ID: 450242
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 3 Vol. 81; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ABLATION
BREMSSTRAHLUNG
ELECTRON EMISSION
ELECTRON TEMPERATURE
EXTREME ULTRAVIOLET RADIATION
FLUORESCENCE
IONIC CRYSTALS
LASER RADIATION
MAGNESIUM OXIDES
NEUTRAL PARTICLES
time resolved spectra