Fourier transform infrared spectrometer for a single aerosol particle

Gideon Sageev Grader, Richard C. Flagan, John H. Seinfeld, Stephen Arnold

Research output: Contribution to journalArticlepeer-review


A spectrometer is reported here for obtaining the infrared spectrum of a single aqueous aerosol particle by a Fourier transform technique. The particle is held in an electrodynamic balance and irradiated simultaneously by the infrared output from a Michelson interferometer and the visible light from a dye laser. The size of the particle is modulated by chopping the IR beam, and the resulting visible scattered light fluctuation is detected at 90° with a photomultiplier tube. The amplitude of the scattered light fluctuation is measured with a lock-in amplifier at each interferometer mirror position. The electronic circuitry for stepping the interferometer mirror is presented and discussed. Inverting the lock-in signal by a discrete fast Fourier transform routine (FFT) yields the particle absorption spectrum. The resulting spectrum for an (NH4)2SO4 droplet is presented.

Original languageEnglish (US)
Pages (from-to)584-587
Number of pages4
JournalReview of Scientific Instruments
Issue number4
StatePublished - 1987

ASJC Scopus subject areas

  • Instrumentation


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