Terahertz difference frequency response of pdd in two-laser experiments

Abstract

In previous work we reported observations of a thermal response from Pd cathodes electrolyzed in heavy water stimulated by a single diode laser. In more recent experiments, stimulation was done using two overlapping weak laser beams, and the cell was observed to respond to the difference frequency. The cell responded to three difference frequencies in the THz range at 8.2 THz, at 15.1 THz, and at 20.8 THz. The first two of these frequencies can be associated with optical phonon frequencies of PdD with zero velocity. We examine the conjectures that the response at 20.8 THz is due to deuterium in vacancies in the gold coating, or due to hydrogen contamination.