Abstract
Abstract. Using the aerosol and cloud simulation chamber AIDA, we investigated the laser filament induced particle formation in ambient air, humid synthetic air, humid nitrogen, argon–oxygen mixture, and pure argon in order to simulate the particle formation under realistic atmospheric conditions as well as to investigate the influence of typical gas-phase atmospheric constituents on the particle formation. Terawatt laser plasma filaments generated new particles in the size range 3 to 130 nm with particle production rates ranging from 1 × 107 to 5 × 109 cm−3 plasma s−1 for the given experimental conditions. In all cases the particle formation rates increased exponentially with the water content of the gas mixture. Furthermore, the presence of a few ppb of trace gases like SO2 and α-pinene clearly enhanced the particle yield by number, the latter also by mass. Our findings suggest that new particle formation is efficiently supported by oxidized species like acids generated by the photoionization of both major and minor components of the air, including N2, NH3, SO2 and organics.
Highlights
M ticle yield by number, the latter by mass
The new particle formation occurs even in humid inert gas atmospheres in which it is most likely driven by the inevitable presence of lower ppb levels of volatile organic trace contaminants
Adding oxygen to the inert gas reduced the particle production rate by an order of magnitude, which is consistent with the high electron scavenging efficiency of oxygen, reducing the plasma reactivity
Summary
M ticle yield by number, the latter by mass. Our findings in the plasma trail left behind by the laser filaments. In recent years femtosecond laser pulses fired into the atmosphere have shown to generate self-guided filaments (Kasctroantidointi.oTnsheweitxhpeerxitmreemnOteslycweleorawenpbeaSrcfkocgrrmioeeundndcinepathrteicllaergceo-nscceanleparian et al, 2003; Couairon and Mysyrowicz, 2007; Bergeaerosol and cloud chamber AIDA (Aerosol Interaction and et al, 2007; Kasparian and Wolf, 2008; Chin et al, 2005) in Dynamics in the Atmosphere) (Mohler et al, 2003; Schnaiter a dynamic balance between Kerr self-focusing and defocus- et al, 2012) under illumination by the TW-class mobile ing by the self-generated plasma and/or negative higher order laser system Teramobile (Wille et al, 2002). Trace gases were sampled via Teflon tubes (FEP, 4 mm inner diameter) placed 5 cm away from the central AIDA axis and the laser beam, directly above the mixing fan. Aerosol particles were sampled through stainless steel tubes located ∼ 15 cm above the laser beam and 60 cm away from the central axis of the AIDA chamber, towards the laser exit window. Cloud droplets were sampled via vertical stainless steel tubes in the bottom of the AIDA chamber
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