闪锌矿的吸收光谱和颜色的本质

本文采用电子吸收光谱和分子轨道（MO）－能带理论模型，系统地研究了不同颜色的闪锌矿呈色的机理和本质。闪锌矿由于其形成条件不同，所含杂质元素各异而颜色变化。黑色闪锌矿含Fe高，其颜色是由于以配位体硫为特征的非键轨道2e到Fe^2 的晶体场型轨道的电子转移在500nm产生吸收所致。只有闪锌矿含Fe低（＜1％）时，它才可具有其他颜色，黄色与受主能级Cu^ 到导带或价带到施主能级Ga^3 的电子跃迁在410nm产生吸收有关；绿色是Co^2 的晶体场跃迁^4A2→^4T2(P)在700nm附近产生的吸收峰所致；红色可能与受主能级Hg^ 到施主能级Ga^3 的电子跃迁在470nm产生宽吸收带有关。当闪锌矿的吸收光谱有其中两个吸收带叠加时，它具有过渡的颜色，如黄绿色或绿黄色、桔黄色或桔红色，主要色调取决于两个吸收带的相对强度。

ABSORPTION SPECTRA AND COLORATION OF SPHALERITE

The mechanism of coloration of sphalerite has been studied with the help of optical absorption spectroscopy and the single electron MO-energy band model. The diversity in color of sphalerite is attributable to different impurity elements and different formation conditions. Black sphalerite high in iron content is attributed to the charge transfer between the non-bonding orbital 2e characterized by coordinated sulfur 3p electron and the crystal field orbital of Fe~(2+), which causes an absorption edge at about 500nm. Other colors can be seen only in sphalerite with the lower content of iron (<1%). Yellow color is perhaps associated with the electron transition from the acceptor level Cu~+ to the conduction band or from the valence band to the donor level Ga~(3+). The spin-permitted crystal field transition of Co~(2+), forming absorption bands at about 700nm, may be an explanation for the green color. The red color is due to the wide absorption band at 470nm associated with the electron transition between acceptor level Hg~+ and donor level Ga~(3+). The overlap of the above absorption bands will give rise to other colors of sphalerite, such as yellowgreen, green-yellow, orange-yellow or orange. The basic color is dependent on the relative intensity of absorption bands.