一、引言量子化学自诞生以来,就经受了大量分子光谱数据的考验,实验表明量子化学的正确和有效。近年来光电子能谱的出现,更提供了许多新的数据,进一步推动了量子化学的发展。量子化学的概念和方法,目前已渗透到化学的各个分支,并得到了广泛的应用。例如在有机化学中,轨道、能级及电子密度等概念代替了传统的价键和定域概念。 I. INTRODUCTION Since its birth, quantum chemistry has withstood the test of a large number of molecular spectroscopic data. Experiments show that quantum chemistry is correct and effective. In recent years, the emergence of photoelectron spectroscopy, but also provides many new data, and further promote the development of quantum chemistry. The concepts and methods of quantum chemistry, has now penetrated to the various branches of chemistry, and has been widely used. In organic chemistry, for example, concepts such as orbitals, energy levels and electron densities replace the traditional valence bond and localization concepts.