The highest-energy band containing electrons is called the valence band, and the next higher one is the conduction band. 填有电子而能量最高的能带称为价带,相邻的更高能带称为导带。
Thus, optical-wavelength light can excite an electron at an impurity atom from one discrete state to another without knocking it all the way to the conduction band. 因此,一般的光波可以将杂质原子里的电子从一个离散的能态激发到另一个,而不会把它打到更高的导带。