【作者】 马文荣； 赵桂芝；

【Author】 MA Wen-rong,ZHAO Gui-zhi (Nan Hua University,Hengyang of Hunan Prov.421001,China)

【机构】 南华大学；

【摘要】 ²²²Rn发生衰变产生²¹⁸Po的反冲原子,²¹⁸Po带正电,会快速与空气中的痕量气体或水蒸气形成团簇,或称未结合态,未结合态的²¹⁸Po可以与空气中的其他气溶胶颗粒结合,形成结合态的²¹⁸Po,这在历史上已经得到公认,但是上述过程中带正电的²¹⁸Po在空气中怎样失去电荷发生中和的机制、条件和影响因素等都不太清楚。这个中和过程是静电收集法测氡的一个理论基础,并且也是氡子体剂量估算的一个重要基础。二十多年来这个问题一直受到学者的关注,进行了不断的研究,并取得了很多新的进展。本文详细讨论了中和作用过程中的三种机制——电子俘获机制、小离子重新结合机制和电子转移机制。电子俘获机制是由水的辐射分解产生的羟自由基俘获²¹⁸Po反冲路径上的电子,变成OH,再与Po正离子发生中和;小离子重新结合机制指Po正离子与气体中电离产生的小的负离子结合;电子转移机制指PoO₂⁺形成后,电子从电离能较低的分子转移给电离能较高的PoO₂⁺上发生中和,是直接的电子转移过程。在不同的环境条件（空气中的气体含量、电离强度、温度、空气湿度、氡浓度）和Po离子生成后的不同年龄条件下,上述不同机制发生的程度不同,他们的影响因素也各不相同。更多还原

【Abstract】 After the formation by decay of ²²²Rn,the freshly generated ²¹⁸Po ions in recoil routes are most positively charged and react fast with trace gases and vapors in air and become small particles called clusters or,unattached "decay products",the unattached ²¹⁸Po clusters can react with other aerosol particles and become attached ²¹⁸Po.This process has been accepted in past records.But how the neutralization of the charge ²¹⁸Po happened and the conditions have many uncertainties.This neutralization process is a foundation of radon measurements that depend on electrostatic collection of charged decay products and the dose of radon decay products.This study has been concerned by many scholars in recent years and has obtained many new progresses.Three neutralization mechanisms of ²¹⁸Po were individually described, including electron scavenging by OH radicals formed by radiolysis of water vapor,recombination with small air ions and charge transfer by molecules of lower ionization potential.The three neutralization mechanisms happened differently in different conditions,such as gas concentration in the air,the ionization rate,temperature,the humidity concentration, radon concentration and the age of radon progeny and so on.更多还原