SPECTRALLY RESOLVED ABSOLUTE FLUORESCENCE CROSS-SECTIONS FOR BACILLUSSPORES

Absolute fluorescence cross sections for Bacillus subtilis and B. cere us bacterial spores as both aqueous suspensions and aerosols were meas ured at a number of excitation wavelengths between 228 and 303 nm. The fluorescence was spectrally resolved at each excitation wavelength. e xcitation wavelength for spore fluorescence is between 270 and 280 nm for aqueous suspensions is four times larger than for dry aerosols whe n measured under similar conditions. Measurements on wet aerosols show ed an increase in fluorescence cross section over dry aerosols, indica ting an enhancement of the fluorescence when the bacterial spores are wet. Mie scattering cross sections at 90 degrees to the direction of t he incident radiation and extinction cross sections as a function of w avelength for B. subtilis suspensions and fluorescence cross sections for tryptophan are also reported. (C) 1997 Optical Society of America