RESUMEN
Electron energy distribution functions (EEDFs) were measured with increasing gas pressure in oxygen capacitively and inductively coupled plasmas. It was found that, in the capacitive discharge, abnormally low-energy electrons became highly populated and the EEDF evolved to a more distinct bi-Maxwellian distribution as the gas pressure was increased. This pressure dependence of the EEDF in the oxygen capacitive discharge is contrary to argon capacitively coupled plasma, where--at high gas pressure--low-energy electrons are significantly reduced due to collisional heating and the EEDF evolves to the Maxwellian. The highly populated low-energy electrons at high gas pressure, which was not observed in inductively coupled oxygen plasma, show that collisional heating is very inefficient in terms of the oxygen capacitive discharge. It appears that this inefficient collisional heating seems to be attributed to a low electric field strength at the center of the oxygen capacitive plasma.
RESUMEN
Growth and propagation of the transient planar state in the transition of cholesteric liquid crystals from the homeotropic to the planar state was investigated by both experiments and numerical simulations for planar boundary conditions. Interference fringes observed in the measured reflection spectra during the evolution of the transient planar state have not been reported in the previous study. These interference fringes caused by a Fabry-Perot interferometric structure formed in the cell show that the transient planar state grows from the surfaces and propagates toward the bulk region in the planar sample. Our experimental results for the growth of transient planar state in planar boundary conditions are consistent with the previously reported simulation studies.