SIZE-DEPENDENT MEASUREMENT OF AEROSOL PHOTOEMISSION FROM PARTICLES IN DIESEL EXHAUST

The size dependence of the photoelectric yield is investigated for particles in the exhaust of an oil burner and a diesel engine. This experiment yields information on the relative concentration of polyaromatic hydrocarbons (PAH) on particles of different sizes. For the particles produced by the oil burner the PAH concentration is proportional to beta(D)/D2, where beta(D) is the attachment coefficient and D the particle diameter. This is expected when the PAH concentration is controlled by diffusion flux to the particles. With diesel particles, however, the PAH concentration per unit particle surface is much higher with smaller particles than can be explained by the diffusion model.