The pressure induced reactivity of carbon monoxide was investigated in a wide temperature range (100-400 K) completely avoiding any irradiation of the sample with visible or higher frequency light. FTIR spectroscopy was employed to monitor the reaction and infrared sensors for measuring the pressure. With this approach we have been able to separate the effects of the three variables (P, T and hnu) that establish the conditions for the occurrence of the chemical reaction. A new instability boundary, not affected by the photoactivation of the reaction, is provided. The reaction has been studied in three different crystal phases (epsilon, delta, and beta), but the small differences in the reaction products are ascribable to the temperature changes rather than to the crystalline arrangement. For T<300 K the analysis of the IR spectra reveals the formation of an extended amorphous material formed, according to the vibrational assignment and to the kinetic data, by polycarbonyl linear chains containing a large amount of anhydride groups. For T>or=300 K the formation of carbon dioxide and epoxy rings, and the simultaneous decrease of carbonyl species, let suppose a decarboxylation of the extended solid product. Once exposed to the atmosphere, the reaction product readily and irreversibly reacts with water giving rise to carboxylic groups.
Elementary magnon, libron and vibron excitations as well as combined two-libron excitations of solid
α
oxygen have been investigated by means of Raman scattering at several isobars in
the pressure range up to 1.25 GPa. We deduced the band frequency, bandwidth
and relative band intensity of all modes as a function of temperature and
pressure. On the basis of these results we can exclude the possibility of all
second-order phase transitions in the low temperature, low pressure range of
oxygen stated in the literature. The disappearance of the sublattice magnetization
σ
could be estimated from the frequency of the higher energy magnon mode at the critical
pressure which is in the vicinity of the phase transition from the antiferromagnetic ordered
δ phase to the
non-magnetic ε
phase. The change of several spectroscopic features under increasing pressure
clearly indicates that anharmonic contributions in the libron potential are altered.
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