固体表main能够吸附气体的空位称吸附中心

求吸附率$\theta=\frac N {N_0}$的状态函数

吸附一个分子，系统能量降低，为$-\varepsilon _0$.采用能级指标表示

$$ \Xi=\sum_{N=0}^\infty\sum_se^{-\alpha N-\beta E_s}=\sum_N\sum_l\Omega_{Nl}e^{-\alpha N-\beta E_l} $$

$$ \begin{aligned} \Xi& =\sum_{N=0}^{N_0}\frac{N_0!}{N!\big(N_0-N\big)!}e^{-\alpha N+\beta N\boldsymbol{\varepsilon}0} \\ &=\sum{N=0}^{N_0}\frac{N_0!}{N!(N_0-N)!}{\left(e^{-\alpha+\beta\varepsilon_0}\right)^N} \\ &=\left(1+e^{-\alpha+\beta\varepsilon_0}\right)^{N_0} \end{aligned} $$

将被吸附气体视为理想气体

$$ \frac\mu{kT}=\frac {N_{气}}V{\left(\frac{h^2}{2\pi mkT}\right)}^{3/2}=\frac P{kT}{\left(\frac{h^2}{2\pi mkT}\right)}^{3/2} $$

$$ \begin{aligned}\theta=&\frac{\overline{N}}{N_0}=\frac{1}{1+(kT/P)\Big(2\pi h^{-2}mkT\Big)^{3/2}e^{-\varepsilon_0/kT}}\end{aligned} $$

$\theta-T$.压强低的在下方

$\theta-P$.温度大的在下方