Femtosecond growth dynamics of an underdense ionization front measured by spectral blueshifting

Journal Article · Mon Feb 01 04:00:00 EST 1993 · IEEE Transactions on Plasma Science (Institute of Electrical and Electronics Engineers); (United States)

DOI:https://doi.org/10.1109/27.221098· OSTI ID:6427279

Wood, W M; Siders, C W; Downer, M C ^[1]

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1. Univ. of Texas, Austin (United States)

The authors present a comprehensive report of time-resolved spectral blue shifts of 100-fs laser pulses caused by ionization of atmospheric density N[sub 2] and noble gases subjected to high (10[sup 14]W/cm[sup 2]-10[sup 16]W/cm[sup 2]) light intensities. Included are data for two experiments: (1) self-shifting of the ionizing laser pulses for varying peak intensities, pressures (1-5 atm.), and gas species; and (2) time-resolved blueshifts of a weak copropagating probe pulse for the same range of ionization conditions. The self-shift data reveal a universal, reproducible pattern in the shape of the blueshifted spectra: as laser intensity, gas pressure, or atomic number increase, the self-blueshifted spectra develop from a near replica of the incident pulse spectrum into a complex structure consisting of two spectral peaks. The time-resolved data reveal different temporal dependence for each of these two features. The authors present a quantitative model for a simplified cylindrical focal geometry which explains the presence of the two spectral features in terms of two distinct ionization mechanisms: collisionless tunneling ionization, which dominates early in the ionizing pulse profile, and electron impact ionization, which dominates during the intense maximum of the ionizing pulse. Transient resonant enhancements may also contribute to ionization near the peak of the pulse.

• DOE Contract Number: FG05-92ER40739
• OSTI ID: 6427279
• Journal Information: IEEE Transactions on Plasma Science (Institute of Electrical and Electronics Engineers); (United States), Journal Name: IEEE Transactions on Plasma Science (Institute of Electrical and Electronics Engineers); (United States) Vol. 21:1; ISSN ITPSBD; ISSN 0093-3813
• Country of Publication: United States
• Language: English

Related Subjects

661300* -- Other Aspects of Physical Science-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COHERENT RADIATION
COLLISIONS
DATA
DOPPLER EFFECT
ELECTROMAGNETIC RADIATION
ELECTRON COLLISIONS
ELEMENTS
EXPERIMENTAL DATA
FLUIDS
GASES
GEOMETRY
INFORMATION
IONIZATION
LANGMUIR FREQUENCY
LASER RADIATION
MATHEMATICAL MODELS
MATHEMATICS
NITROGEN
NONMETALS
NUMERICAL DATA
PHOTOIONIZATION
PLASMA
PULSES
RADIATION SOURCES
RADIATIONS
RARE GASES
SPECTRAL SHIFT
USES