The UPS and IPES are the most powerful and direct technologies to study the structure of occupied and unoccupied energy band below and above the Fermi level in the solid state material, respectively.

• 而光电子频谱及电子光频谱为现今研究固态材料在费米能阶上下佔态及未佔态轨域最强而有力且直接的方式。