Daughter recoil

In 1904 it was observed by H. Brooks that measurements on Po (RaA), obtained from radon, led to a contamination of the detection chamber by Pb (RaB) and Bi (RaC). This was explained by Rutherford as being due to daughter recoil in the a-decay of in the sequence (written symbolically) ... 

In isomeric decay the 7-energy is often so small that the daughter recoil is negligible. For example... 

Figure 5. Ejection of daughter nuclide out of a grain due to recoil. Only a fraction of the nuclides located in a cone will be ejected for a given range 8. As shown on the diagram, at a distance x from the surface of the grain, the only nuclide to escape by recoil will be located in a cone with an angle a.

Figure 2. (A.) The radionuclides in an aquifer are divided into three reservoirs groundwater, the host aquifer minerals, and adsorbed onto active surfaces. Also shown are the processes adding to a daughter nuclide (closed circles) in the groundwater of weathering, advection, recoil from decay of parent atoms ( P ) in the aquifer minerals, and production by parent decay, the processes of losses of a radionuclide of advection and decay, and exchange between dissolved and adsorbed atoms.

Input by production from sorbed parent atoms. Daughter atoms recoiled during... 

Adsorbed nuclides. Obtaining a solution to Equation (1) requires knowledge of the absorbed abundance of the nuclide of interest (Iads)- Assuming that steady state abundances have been achieved at each location, supply by adsorption is balanced by desorption and decay. No supply is expected to occur by decay of adsorbed parent atoms in the cases where a recoil drives daughters instead into solution or into the underlying mineral (although modification may be made in the case of p decay). Then,... 

From the diversity of potential sites for U and Th, it is clear that the weathering release of and Th, as well as of the recoil and leaching release of daughter nuclides, must be determined for each site. Nonetheless, most studies assume that and Th have similar distributions, so that the values for si (the fraction released by recoil) and wi (the weathering release constant) is assumed to be approximately equal for all nuclides I. 

While it is expected that the source rocks for the radionuclides of interest in many environments were deposited more than a million years ago and that the isotopes of uranium would be in a state of radioactive equilibrium, physical fractionation of " U from U during water-rock interaction results in disequilibrium conditions in the fluid phase. This is a result of (1) preferential leaching of " U from damaged sites of the crystal lattice upon alpha decay of U, (2) oxidation of insoluble tetravalent " U to soluble hexavalent " U during alpha decay, and (3) alpha recoil of " Th (and its daughter " U) into the solute phase. If initial ( " U/ U).4 in the waters can be reasonably estimated a priori, the following relationship can be used to establish the time T since deposition,... 

The chemical behavior of U and its daughter nuclides in the ocean environment was extensively studied in the 1960s and 1970s and has been well summarized (Cochran 1992). The most important mechanism by which nuclides are separated from one another to create disequilibrium is their differing solubility. For U, this solubility is in turn influenced by the redox state. The process of alpha-recoil can also play an important role in producing disequilibrium. 

Decay of on the continents causes a-recoil of the immediate daughter, " Th, which quickly decays to This process leads to ( " U/ U) above the secular... 

The paper summerizes the experimental data on the equilibrium factor, F, the free fraction, fp, the attachment rate to the room air aerosol, X, the recoil factor,, and the plateout rates of the free, qf, and the attached, q3, radon daughters, determined in eight rooms of different houses. In each room several measurements were carried out at different times, with different aerosol sources (cigarette smoke, stove heating etc.) and under low (v<0.3 It1) and moderate (0.3[Pg.288]

Kolerskii, S.V., Yu.V. Kusnetsov, N.M. Polev and L.S. Ruzer, Effect of Recoil Nuclei being Knocked of Aerosol Particles onto Free-Atom Concentrations of Daughter Emanation Products, Izmeyitel naya Tekhnika 10 57-58 (1973). 

Figure 5. Relative standard deviation on the fitting of the deposition rate of the unattached daughters (Xun) and on the fitting of the ventilation rate (Xvent)> calculated by means of a Monte- Carlo simulation model. The lower curve is obtained with counting statistics alone. The upper curve includes one hour time fluctuations on the input parameters, with 10% rel. stand, dev. on X, un (15/h), a(.35/h), Vent(.45/h) and radon cone. (50 bq/m ) and 2% on recoil factor (.83), penetration unattached (.78) and flow rate (28 1/min).

It has been reported for many years that condensation nuclei can be produced by ionizing radiation. Recent studies have improved the measurement of the activity size distribution of these ultrafine particles produced by radon and its daughters (Reineking, et al., 1985 Knutson, et al., 1985). It seems that the Po-218 ion is formed by the radon decay, is neutralized within a few tens of milliseconds, and then attached to an ultrafine particle formed by the radiolysis generated by the polonium ion recoil. Although there will be radiolysis along the alpha track, those reactions will be very far away (several centimeters) from the polonium nucleus when it reaches thermal velocity. The recoil path radiolysis therefore seems to be the more likely source of the ultrafine particles near enough to the polonium atom to rapidly incorporate it. 

Since the subsequent B-decays of Pb-212 and Pb-214 4- Bi-214 do not result in significant recoil (Mercer, 1976), the alpha measurement of Po-214 and the Pb-212 daughters is in reality tracing the aerosol distribution of a Rn-220 daughter atom (Pb-212) which has condensed only once and a Rn-222 daughter atom (Pb-214) that has probably condensed more than once. This stability of the Pb isotopes is the basis for our generic reference to Pb-212 and Pb-214 distributions. 

A Recoil Model That Accounts for The Pb-214 Shift. The following equations describe an empirical model that outlines the hypothesis more formally. First, the radon daughters are defined in terms of their atmospheric distributions at some time during their life ... 

For A, the fraction of the total Po-218 that attaches before decay, the recoiling daughter Pb-214 produced in any size interval can fractionate as follows ... 

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