Broberg, Theodore Waldo, authorShe, C. Y., advisorEdwards, David F., advisorKrueger, David A., committee memberRaich, J. C., committee member2021-09-072021-09-071972-01https://hdl.handle.net/10217/233867Laser Raman spectra for NH4H2PO4 (ADP) and KH2PO4 (KDP) are presented as a function of temperature in the region above the phase transitions. Evidence is presented confirming the existance of strong coupling between the proton B2 tunneling mode and the B2 optical phonon mode in both crystals. The spectra were fit to a coupled oscillator function and the relevant fitting parameters are presented. The Debye relaxation time and soft mode frequency for the overdamped mode as well as the static dielectric susceptibility are plotted as a function of temperature. Soft mode behavior in both crystals displays the ω2 α(T-Tc') dependence. For KDP Tc' was determined to be 30°K. Room temperature spectra are presented for KDP and ADP, and five of the six optical phonon modes are identified. The (PO4)3- ion modes are observed to split under the local crystalline field of S4 symmetry and a librational mode of the (NH4)+ ion is resolved.doctoral dissertationsengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.Raman effectText