Statistics of electric charging of α-active aerosols

Abstract

Electric charging processes have a large effect on the behavior of aerosols: spreading in space and precipitation. The aerosols are effectively charged by ionizing radiation, acting on the particles and the surrounding atmosphere. The sources of irradiation could be external or internal (situations when the particles themselves are radioactive are possible). In the latter cases, charging of a and 13-active aerosols is of greatest interest; charging by means of"/-decay is insignificant. The statistics of the charging of 13-active aerosols is discussed in [1].Our objective in this paper is to calculate the distribution functions of the electric charges of a-active particles in a bipolar atmosphere by the method of detailed balance of the charge states of particles [1]. The main feature is that under conditions of a-decay of the constituent nuclei of the aerosol material -40 secondary electrons emanate from micron-size particles [2], and as a result a particle acquires a positive charge. For this reason, in contrast to the case of t3-active particles. multiple charge transfers between charge states must be included in the analysis.We shall consider a quite rarefied aerodtspersed system, in which collisions of aerosol particles (and corresponding charge exchange) can be neglected. The charge on the aerosol particles can change as a result of absorption of electrons or ions from the atmosphere as well as emission of a-particles and secondary electrons.The interaction of the particles can only be mediated through the common ionic atmosphere, and for this reason the charge distribution over particles in different size fractions do not depend on one another. Let the system contain N particles with radius r. Let Nk(t ) be the number of particles which at time t have electric charge ek. k = 0, + 1, +2 ..... where e ~s +~ an elementary electric charge. At any time the relation ~ Nk(t ) = N, which follows from the conservation of the number k=-~ of particles is satisfied.We introduce the probability of a change in the charge state of a particle per unit time as WkJ, where ke is the charge of the particle before the change and je is the charge in the charge as a result of a single recharging act.If the state of the particles with charge k is represented graphically by nodes on an axis, then the process of charge exchange can be associated with a diagram (see Fig. 1).It is pertinent here to introduce the concept of a current along the axis of charge states. Consider an arbitrary section between neighboring states (for example, k--1 and k). Then the current of states through this section is ~'k-~. k = oo = Y~ ~ (Wlk-! Nk-l --WkkJ-t +INk -1 +t)" In the stationary state this current is equal to zero. For the case of fixed (with respect l=l i=l to the number of charges) emission of electrons (for example, one-electron emission) the equation ~b k_t.k = 0 gives a unique relation between N k and Nkd. In the case of the statistics of charges emerging from an aerosol particle in the process of decomposition, not only the closest neighb...

Behavior of radioaerosols formed by evaporation of 137Cs131I and 137CsOH from the metal surface in an electrostatic field

“…The β-decay of radioactive fission products imparts a positive charge to aerosols. The behavior of radioactive aerosols and their electrification have been studied in sufficient detail [6][7][8][9].…”