Spectroscopic Study of Ultrashort Pulse Laser-Breakdown Plasmas in Air

Time-resolved visible spectroscopy of plasmas produced by laser breakdown of air using femtosecond Nd laser pulses (50–300 mJ, 500 fs) reveals features not observed with nanosecond laser pulses. Emission is initially dominated by molecular lines, specifically the second positive system of N2 and the first negative system of N2+. This is followed by continuum emission with a growth time of ∼3 ns and a decay time of ∼30 ns. Atomic lines of N and O emerge from the decay of the continuum and last up to 1 μs; only faint ionization lines are observed. Several of the atomic lines are initially strongly broadened, narrowing over a period of 100 ns.

[1]  S. Merola,et al.  Time-resolved spectral and spatial description of laser-induced breakdown in air as a pulsed, bright, and broadband ultraviolet-visible light source. , 1998, Applied optics.

[2]  I. A. Kossyi,et al.  Kinetic scheme of the non-equilibrium discharge in nitrogen-oxygen mixtures , 1992 .

[3]  W. Rawlins,et al.  Spectroscopic investigation of laser-initiated low-pressure plasmas in atmospheric gases. , 1982, Applied optics.

[4]  R. Nordstrom.  Study of Laser-Induced Plasma Emission Spectra of N2, O2, and Ambient Air in the Region 350 nm to 950 nm , 1995 .

[5]  D. Keefer,et al.  Experimental study of a stationary laser−sustained air plasma , 1975 .

[6]  William L. Barr,et al.  Spectral Line Broadening by Plasmas , 1975, IEEE Transactions on Plasma Science.

[7]  F. H. Read,et al.  Measurement of the lifetimes of ionic excited states using the inelastic electron-photon delayed coincidence technique , 1975 .

[8]  Jean-Claude Kieffer,et al.  Filamentation of ultrashort pulse laser beams resulting from their propagation over long distances in air , 1999 .

[9]  G. Herzberg,et al.  Molecular Spectra and Molecular Structure , 1992 .

[10]  J. G. Parker,et al.  Experimental investigation of electrical breakdown in nitrogen and oxygen induced by focused laser radiation at 1.064 μ , 1982 .

[11]  D. Comtois,et al.  Modeling the triggering of streamers in air by ultrashort laser pulses , 2000 .

[12]  D. Lorents,et al.  An Introduction to Gas Lasers: Population Inversion Mechanisms , 1976 .

[13]  K. B. Mitchell.  Fluorescence Efficiencies and Collisional Deactivation Rates for N2 and N2+ Bands Excited by Soft X Rays , 1970 .

[14]  Leon J. Radziemski,et al.  Time-resolved laser-induced breakdown spectrometry of aerosols , 1983 .

[15]  See Leang Chin,et al.  Re-focusing during the propagation of a focused femtosecond Ti:Sapphire laser pulse in air , 1999 .

[16]  F. R. Simpson,et al.  Absolute cross sections for electron excitation of the second positive bands of nitrogen , 1969 .

[17]  M. Miki,et al.  Guiding of electrical discharges under atmospheric air by ultraviolet laser‐produced plasma channel , 1996 .

[18]  R. Anderson,et al.  Excitation of the C 3Πu state of N2 by electron impact , 1975 .

[19]  C. Ferreira,et al.  Kinetic model of a low-pressure N/sub 2/-O/sub 2/ flowing glow discharge , 1995 .