Fluorescence of Atmospheric Aerosols and Lidar Implications

Abstract

The fluorescence of aerosols in the ambient atmosphere has been monitored in situ using cw argon ion laser excitation in bands of 50 nm and 100 nm over the spectral region of 560-810 nm. The observed broadband aerosol fluorescence may limit lidar (laser radar) determinations of pollutants. The limitation can be overcome by a method in which the aerosol fluorescence excited at two wavelengths is constant while the molecular signals differ. The effectiveness of the technique has been demonstrated by in situ measurements of atmospheric nitrogen dioxide (NO(2)) in the presence of aerosols.

A recursive transfer-matrix solution for a dipole radiating inside and outside a stratified sphere

“…In general, the angular distribution involves more terms in the series expansion. These additional terms will contain information about the sphere radius, which is of interest to cell biology [7,9,10] and atmospheric physics [6,8]. For example, atmospheric aerosols may fluoresce [8] and this might be used to provide a means for their chemical identification and to measure their content in the atmosphere.…”

“…Later on, Raman microprobe analysis of particulates was used for identification of biological particles in fluorescence-activated flow of cytomeres [7]. The inelastic scattering of species embedded within a spherical particle is also of considerable interest in studies employing light detecting and ranging (LIDAR) for remote sensing of both molecular and particulate constituents of atmosphere [6,8]. Indeed, atmospheric aerosols may fluoresce and that may be used to provide a means for chemical identification of ambient aerosols and to measure aerosol content in the atmosphere [8].…”

“…The inelastic scattering of species embedded within a spherical particle is also of considerable interest in studies employing light detecting and ranging (LIDAR) for remote sensing of both molecular and particulate constituents of atmosphere [6,8]. Indeed, atmospheric aerosols may fluoresce and that may be used to provide a means for chemical identification of ambient aerosols and to measure aerosol content in the atmosphere [8]. As another example, the particle may be a biological cell which has been tagged with fluorescent molecules that attach to the DNA, the cytoplasm, or to the cell membrane.…”

Remote nocturnal bird classification by spectroscopy in extended wavelength ranges

“…Examples of standard applications are the mapping of aerosols [33], clouds [34], temperature [35], and wind speed [36] in the atmosphere. Lidar is also used for gas concentration measurements [37][38][39] and fluorescence studies of, e.g., aerosols [40] and hard targets such as buildings, water compounds, and plants [41,42]. The technique is well documented, and overviews can be found in e.g., [43,44].…”

Prototype FAGE determination of NO2

“…This was a limiting factor in previous attempts to measure NO2 with laser-induced fluorescence at atmospheric pressure [Gelbwachs and Birnbaum, 1973]. To a large extent, aerosols should be discriminated by the temporal and spectral specificity of the FAGE system since aerosols must absorb at 532 nm and fluorescence with microsecond lifetimes in order to present significant interference to the NO z-FAGE system.…”