For the first time, the evolution ofluminescence from rare gases was studied as a function of number density. Synchrotron radiation served as a light source for selective and pulsed excitation of the samples. The excitation spectra confirm previous results on perturbed Rydberg states and exciton appearance in dense media. In time-resolved emission spectra the peak energies and widths of the luminescence bands were followed. The energy separation between the fast and slow components is found to be density independent. A model proposed by Cheshnovsky et al. [Chern. Phys. Lett. 15, 475 (1972)] accounts for the change in peak width with temperature. Both lifetimes decrease with increasing density. The data extrapolate to 3.3 ± 0.1 ns (Ar); 3.4 ± 0.1 ns, 270 ± 5 ns (Kr); 4.5 ± 0.1 ns, 100 ± 5 ns (Xe) for the low density limit. For the solid at the triple point, we obtain 1.3 ± 0.1 ns, 82 ± 5 ns (Kr) and1.1 ± 0.1 ns, 18.5 ± 0.5 ns (Xe). Theories on density dependence oflifetimes give only a qualitative description of the experimental results.
Direct pattern transfer onto poly(vinylidene fluoride) was achieved by using x-ray photons from a synchrotron radiation source. Quadrupole mass spectrometry and ultraviolet photoemission spectroscopy, combined with ab initio molecular orbital calculations, were employed to investigate the mechanism of direct photomicromachining. The mass spectrometry identified H2, F, and HF as the etched products, with no carbon containing species being detected. The changes in photoemission spectra due to photodegradation were analyzed by comparison with ab initio molecular orbital calculations. This analysis indicated that a high degree of conjugation is generated in the degraded polymer due to the loss of fluorine atoms. It is concluded that the mechanism of direct photomicromachining is ascribable to the shrinking of the irradiated polymer region due to defluorination and the generation of conjugation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.