Vol. 27, issue 01, article # 14

Abstract:

There are two types of photophoretic forces, the DTS- (Crookes) and the Da-force (Knudsen). This paper deals with the fundamental problem of distinguishing by experiment between both forces by using their different dependencies on pressure. We explored gravito-photophoresis of individual particles from three materials differing in their physical properties (carbon amorphous, crystalline, aluminium). On the grounds of available aerosol theory representation of the majority of cases is not feasible. Resolvable special cases and the data in their entirety, however, secure unambiguously earlier hypotheses that the force of gravito-photophoresis is normally caused by differences in the accommodation coefficient (Da) over the surface. That conclusion is confirmed by a method for determining the size of particles from the force-pressure diagram which yields reasonable results. Hypothetical application of gravito-photophoresis to atmospheric aerosols now obtains empirical corroboration. Some aluminium particles surprisingly show changes in behaviour depending on pressure and irradiance. Here, the levitating force is determined not only (as usual) by the momentary irradiation, but also by the previous history of this factor. We assume that with some metals the irradiation can induce variations in the accommodation coefficient. Results of the investigations are applied to clarifying lasting problems of electro-photophoresis and apparent longitudinal photophoresis.

Keywords:

aerosols, vertical transport, photophoresis, radiometer forces, accommodation

References:

1. Preining O. Die Erscheinungen der Photophorese // Staub. 1955. V. 39. P. 45–64.
2. Rohatschek H. Theorie der Photophorese – Ergebnisse und Probleme // Staub. 1955. V. 42. P. 607–643.
3. Preining O. Photophoresis // Aerosol Science. Ed. by C.N. Davies. London: Academic Press, 1966. P. 111–135.
4. Rohatschek H. History of photophoresis // History of Aerosol Science / Eds. by O. Preining and E.J. Davis. Wien: Verlag der Österreichischen Akademie der Wissenschaften, 2000.
5. Schinner A., Rohatschek H. Stochastic processes associated with photophoresis // J. Aerosol Sci. 2008. V. 39. P. 549–553.
6. Crookes W. On (attraction and) repulsion resulting from radiation // Phil. Trans. 1874–1880. V. 164. P. 501–527; V. 165. P. 519–547; V. 166. P. 325–376; V. 168. P. 243–318; V. 170. P. 87–164.
7. Knudsen M. Radiometer pressure and coefficient of accommodation // D. Kgl. Danske Vidensk. Selskap, Math.-Fys. Medd. 1930. V. 11, N. 1. P. 1–75.
8. Rubinowicz A. Radiometerkräfte und Ehrenhaftsche Photophorese (I and II) // Ann. Phys. 1920. V. 62, N. 4. P. 691–715, 716–737.
9. Rohatschek H. Über die Kräfte der reinen Photophorese und der Gravitophotophorese // Acta Physica Austriaca. 1956. V. 10. P. 267–286.
10. Rohatschek H. Semi-empirical model of photophoretic forces for the entire range of pressures // J. Aerosol Sci. 1995. V. 26. P. 717–734.
11. Ehrenhaft F., Reeger E. Sur la photophorèse transversale // Comptes Rendus Acad. Sci. 1951. V. 232. P. 1922–1924.
12. Wilflinger E. Über die Abhängigkeit der Elektrophotophorese von der Lichtintensität und vom Gasdruck // Z. Phys. 1931. V. 71. P. 658–677.
13. Lustig A., Söllner A. Über Photophorese von Silberpartikeln // Z. Phys. 1932. V. 79. P. 823–842.
14. Arnold S., Pluchino A.B., Leung K.M. Influence of surface-mode-enhanced local fields on photophoresis // Phys. Rev. A. 1984. V. 29. P. 654–660.
15. Rohatschek H. The role of gravitophotophoresis for stratospheric and mesospheric particles // J. Atmos. Chem. 1984. V. 1. P. 377–389.
16. Rohatschek H. Levitation of stratospheric and mesospheric aerosols by gravito-photophoresis // J. Aerosol Sci. 1996. V. 27. P. 467–475.
17. Pueschel R.F., Verma S., Rohatschek H., Ferry G.V., Boiadjieva N., Howard S.D., Strawa A.W. Vertical transport of anthropogenic soot aerosol into the middle atmosphere // J. Geophys. Res. 2000. V. 105. P. 3727–3736.
18. Cheremisin A.A., Vassilyev Yu.V., Horvath H. Gravito-photophoresis and aerosol stratification in the atmosphere // J. Aerosol Sci. 2005. V. 36. P. 1277–1299.
19. Krauss O., Wurm G. Photophoresis and the pileup of dust in young circumstellar disks // Astrophys. J. 2005. V. 630. P. 1088–1902.
20. Rohatschek H. Zur Theorie der Gravitophotophorese // Acta Physica Austriaca. 1956. V. 10. P. 227–238.
21. Zulehner W., Rohatschek H. Photophoresis of nonspherical bodies in the free molecular regime // J. Colloid Interface Sci. 1990. V. 138. P. 555–564.
22. Rohatschek H. Zur Dynamik der Photophorese // Acta Physica Austriaca. 1969. V. 30. P. 57–82.
23. Happel J., Brenner H. Low Reynolds Number Hydrodynamics. N.Y.: Prentice-Hall, Englewood Cliffs, 1965.
24. Rohatschek H., Zulehner W. The resistance force on nonspherical particles in the free molecular regime // J. Colloid Interface Sci. 1987. V. 119. P. 378–387.
25. Rohatschek H. Direction, magnitude and causes of photophoretic forces // J. Aerosol Sci. 1985. V. 16. P. 29–42.
26. Tauzin P. Photophorèse et magnétophotophorèse des particules de fer oméga à différentes pressions // Comptes rendus Acad. Sci. 1950. V. 230. P. 77–79.