2143. Stimulated Brillouin scattering of CO 2 laser radiation from underdense plasma : A A Offenberger et al,J Appl Phys,47 (4), 1976, 1451–1458

Abstract

Thin films of buckminsterfullerene C60 were deposited on KBr(100) at 78 K that were prepared by cleaving in UHV. The thickness of the film was monitored by recording the IR spectrum of C60 at different polarizations. For the first time FTIR spectra of CO and CO2 adsorbed on C60 film were measured under UHV conditions. At pressures <10−9 mbar the transmission spectra of CO2 adsorbed on the C60 film at temperatures below 90 K show a single ν3 absorption peak at 2328 cm−1 with a linewidth (FWHM) of 5 cm−1. At higher CO2 pressures the coverage grows and the linewidth and intensity of the absorption peak increase. A second absorption peak at 2331 ± 1 cm−1 was detected. At still higher pressures multilayer adsorption takes place with absorptions at 2344 and 2380 cm−1 at p-polarization and 2344 cm−1 at s-polarization. A single absorption peak of CO adsorbed on C60 was recorded in transmission at 2134 cm−1 with a linewidth of 5 cm−1 at temperatures below 40 K. With increasing CO pressure a peak shift to 2138 cm−1 and an enhancement of the linewidth to 10 cm−1 was observed. Still higher pressures lead to multilayer adsorption with absorptions at 2142 and 2139 cm−1 at p-polarization and 2139 cm−1 at s-polarization. All absorptions detected, including the C60 spectra, possess higher intensities at s-polarization than at p-polarization. At an angle of incidence of 45° the ratio of the integrated absorption (As/Ap) at s-polarization and p-polarization respectively is 1.3.