title: Electrolytic coloration below 0°C and spectral properties of ammonium alum crystals using a pointed anode.
abstract: Ammonium alum crystals are colored electrolytically below 0°C and under various voltages using a pointed anode and a flat cathode. SO2(-), O3(-), O2(-), O(-) hole-trapped centers and O(0), O(2-), H(+) radicals are produced in colored ammonium alum crystals. The absorption bands of the SO2(-) and O3(-) hole-trapped centers are observed in the absorption spectra of the colored ammonium alum crystals. The hole-trapped centers and radicals come mainly from the electric-field-induced decomposition of the SO4(2-) radicals and crystalline water molecules. Current is measured during electrolytic coloration. Electron exchanges from electrons and small charged radicals to electrodes induce complete current.
authors.affiliation: Department of Physics, Tianjin University, Tianjin 300072, PR China. Electronic address: jthgu@163.com.
authors.forename: Hongen
authors.initials: H
authors.lastname: Gu
authors.affiliation: Department of Physics, Tianjin University, Tianjin 300072, PR China.
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Hao
mesh_terms: D000534:Alum Compounds / Q000737:chemistry*; D004566:Electrodes; D004572:Electrolysis; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000534:Alum Compounds; C059726:aluminum ammonium sulfate
keywords: 0°C; Alum crystal; Color center; Electrolytic coloration