X-Ray Photoemission Study of Orthorhombic Selenium; a New Allotrope of Crystalline Selenium

Abstract

In order to study the molecular species of a new allotrope of crystalline selenium (orthorhombic Se), X-ray photoelectron spectroscopy (XPS) has been applied to it for the first time. A comparison of the XPS spectrum of orthorhombic Se with those of rhombohedral and monoclinic Se consisting of Se 6 and Se 8 ring molecules respectively almost excluded the possibility that orthorhombic Se may consist of both Se 6 and Se 8 ring molecules. The CNDO molecular orbital calculations of the electronic structure for several Se 7 ring molecules of various structures suggest that orthorhombic Se is composed of a chair-type Se 7 ring molecule.