Photo-Thermal Detection of the Onset of Photo-Chemical Nucleation (Laser-Snow) in Vapor.
Abstract
The phenomenon of photochemical nucleation of particles (also called Laser-snow) has been observed by many workers, for example, in metal vapor systems and in organic vapors. Although this laser-snow effect seems to occur generally under the right excitation, temperature and pressure conditions, the phenomenon remains poorly understood. One problem is a lack of method for detecting the onset of photo-nucleation of particles, which has up to now been detected, e.g., by light-scattering, or electrostatic deflection. We believe that photo-nucleation should result in a large amount of heat released at the excitation laser beam, due, for example, to heat of condensation, and hence should be detectable by noncontact photothermal means. We report here a first experiment for such detections by using Thermal Lensing (TL) and by Optoacoustic Laser-beam Deflection (OLD). The present experiment is performed in a carbon disulphide vapor at room temperature and reduced pressures. Originator furnished keywords include: Nucleation, aerosol, photo-chemistry, photo-thermal, carbon disulphide, thermal lens, laser beam deflection.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 28, 1984
- Accession Number
- ADA150111
Entities
People
- A. C. Tam
- H. Sontag
- I. Hussla
Organizations
- International Business Machines Corporation (Armonk, NY)