真空系统中CO的置换解吸及对质谱分析的影响

CO Displacement Desorption in Vacuum and Its Influence on the Mass Spectroscopy

当样品气体引入真空系统后，原壁面吸附的气体将被引入气体快速地置换而解吸出来，从而造成真空室内气体组分严重失真于样品气体，这对静态进样的质谱分析尤为严重。极限真空为 １× １０－５ Ｐａ的不锈钢真空系统充入Ｈｅ，Ｎｅ或Ａｒ后，ＣＯ的解吸速度比未充气时提高８倍，Ｈ２和ＣＨ４的解吸速度更快。这种置换吸附和解吸作用有可能用于研究真空装置内某些吸附气体的快速除气，采用预充气法提高充气器件内气体的纯度和采用热封离法提高真空器件内的真空度等措施均基于这个原理。

Injection of some inert gases, such as, helium, neon and argon, usually result in rapid displacement desorption of the gaseous specimen absorbed by the inner surfaces of the vacuum system. For instance, inside a stainless vacuum chamber in a base pressure of 1 × 10 - 5 Pa, injection of the inert gas, He, Ne or Ar leads to an incras of the desorption rate of CO by 8 times. For the cases of hydrogen and methane, the inert gas induced desorption can be much higher than that of CO. On the one hand, this can be a serious problem because it inversely distort the gaseous compositions of the vacuum chamber in a mass spectroscopic analysis. On the other hand, the effect has technological interest in many applications. For instance, pre-filling of inert gas results in rapid outgassing of the inner surfaces of vacuum system or vacuum electronic devices to improve its vacuum. For a gas-filled devices, pre-filling of inert gases may better the purity of the gas to be filled in the device.