Abstract: A method of determining optical absorption and emission spectra from a crystal or non-crystalline fiber sample includes directing a laser light source to a side of the fiber sample and measuring fluorescence intensity at various positions along the crystal fiber sample, and then directing a broadband light source through the ends of the crystal fiber sample and measuring absorption in a region of no fluorescence. The preferred apparatus for carrying out the method includes a broadband light source to generate measurable absorption outside the region of fluorescence and a laser light source for generating measurable absorption in the region of fluorescence.

Abstract: A method for determining the potential of zero charge of an unpowdered semiconductor material. The semiconductor material is used as the working electrode 12 of a standard three-electrode photoelectrochemical cell 11. The onset potential of the semiconductor material is measured at several different cell temperatures. The slope of the graph of onset potential versus temperature is used to compute the potential of zero charge.

Abstract: Photoelectrochemical cells employing chalcogenophosphate (MPX.sub.3) photoelectrodes are disclosed, where M is selected from the group of transition metal series of elements beginning with scandium (atomic number 21) through germanium (atomic number 32) yttrium (atomic number 39) through antimony (atomic number 51) and lanthanum (atomic number 57) through polonium (atomic number 84); P is phosphorus; and X is selected from the chalogenide series consisting of sulfur, selenium, and tellurium. These compounds have bandgaps in the desirable range of 2.0 eV to 2.2 eV for the photoelectrolysis of water and are stable when used as photoelectrodes for the same.