title: Backscatter signatures of biological aerosols in the infrared.
abstract: To develop a deeper understanding of the optical signatures of both biological aerosols and potential interferents, we made field measurements of optical cross sections and compared them to model-based predictions. We measured aerosol cross sections by conducting a hard-target calibration of a light detection and ranging system (LIDAR) based on the Frequency Agile Laser (FAL). The elastic backscatter cross sections are estimated at 19 long-wave infrared (LWIR) wavelengths spanning the range from 9.23 to 10.696 μm. The theoretical modeling of the elastic backscatter cross sections is based on the measured refractive index and size distribution of the aerosols, which are used as inputs into Mie calculations. Both model calculations and experimental measurements show good agreement and also indicate the presence of spectral features based on single particle absorption in the backscatter cross sections that can be used as a basis for discrimination for both standoff and point sensors.
authors.affiliation: The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland 20723, USA. evan.thrush@jhuapl.edu
authors.forename: Evan
authors.initials: E
authors.lastname: Thrush
authors.forename: Nicolas
authors.initials: N
authors.lastname: Salciccioli
authors.forename: David M
authors.initials: DM
authors.lastname: Brown
authors.forename: Karen
authors.initials: K
authors.lastname: Siegrist
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Brown
authors.forename: Michael E
authors.initials: ME
authors.lastname: Thomas
authors.forename: Nathan
authors.initials: N
authors.lastname: Boggs
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Carter
mesh_terms: D000336:Aerosols / Q000737:chemistry*; D001419:Bacteria / Q000378:metabolism; D001435:Bacteriophages / Q000378:metabolism; D002138:Calibration; D007259:Infrared Rays; D015233:Models, Statistical; D008962:Models, Theoretical; D055095:Optics and Photonics; D010316:Particle Size; D012031:Refractometry
chemical_list: D000336:Aerosols