Use of a Fabry-Perot interferometer to isolate pure rotational Raman spectra of diatomic molecules.

We propose to use a Fabry-Perot interferometer (FPI) as a comb frequency filter to isolate pure rotational Raman spectra (PRRS) of nitrogen molecules. In making the FPI's free spectral range equal to the spectral spacing between the lines of nitrogen PRRS, which are practically equidistant, one obtains a device with a comb transmission function with the same period. However, to match the FPI transmission comb completely with the comb of nitrogen PRRS lines one should tune the wavelength of the radiation used to excite the PRRS of nitrogen exactly to the position of any minimum in the FPI transmission comb.

Daytime operation of a pure rotational Raman lidar by use of a Fabry-Perot interferometer.

We propose to use a Fabry-Perot interferometer (FPI) in a pure rotational Raman lidar to isolate return signals that are due to pure rotational Raman scattering from atmospheric nitrogen against the sky background. The main idea of this instrumental approach is that a FPI is applied as a frequency comb filter with the transmission peaks accurately matched to a comb of practically equidistant lines of a pure rotational Raman spectrum (PRRS) of nitrogen molecules. Thus a matched FPI transmission comb cuts out the spectrally continuous sky background light from the spectral gaps between the PRRS lines of nitrogen molecules while it is transparent to light within narrow spectral intervals about these lines.

Experimental validation of the solar aureole technique for determining aerosol size distributions.

This paper describes the inversion procedures by including multiple scattering contributions to almucantar radiance in the solar aureole region and discusses the retrieved size distribution results by comparing them with ground truth measurements. The agreement between the two sets of results is good and provides yet another experimental validation to show that the solar aureole technique is a simple, practical, and accurate method for obtaining the columnar size distribution of atmospheric aerosols. Comparisons between the results obtained by the two approximations--single and multiple scattering--show that the size distribution retrievals obtained by the latter are more accurate than those obtained by the former.