The photophoretic force
The photophoretic force
- Journal of Colloid Science, 19(1), p.50-60, 1964 .
Photophoresis has many times been described qualitatively but quantitative information is scarce. Photophoretic-force measurements have been made with an apparatus that, in essence, compares the force with that of gravity. To the present, only light beams sufficiently intense to develop measurable forces with carbon black particles have been achieved. Unfortunately, these particles were actually agglomerates of smaller particles, making the former's properties such as density, considerably uncertain. Nevertheless, the results, in agreement with radiometer theory, show that the photophoretic force increases exponentially with particle radius. A gas pressure dependence, undetected by several previous investigators, was demonstrated also.
Photophoresis has many times been described qualitatively but quantitative information is scarce. Photophoretic-force measurements have been made with an apparatus that, in essence, compares the force with that of gravity. To the present, only light beams sufficiently intense to develop measurable forces with carbon black particles have been achieved. Unfortunately, these particles were actually agglomerates of smaller particles, making the former's properties such as density, considerably uncertain. Nevertheless, the results, in agreement with radiometer theory, show that the photophoretic force increases exponentially with particle radius. A gas pressure dependence, undetected by several previous investigators, was demonstrated also.