Peaks Of CO2 Research Articles

Optical properties of HgS and HgS : Co2+ crystals

Melt-grown crystals of HgS and HgS : Co2+ were used to measure their optical absorption spectra. The optical energy band gaps of these crystals were 2.030 eV and 1.870 eV at room temperature, respectively. The impurity optical absorption peaks of Co2+ were observed at 4030, 5988, 12285, 12672, and 12905 cm−1. These peaks can be attributed to the electronic transitions between the split energy levels of Co2+ ion located at the Td symmetry site, where the crystal field, Racah, and spin-orbit coupling parameters were given by Dq = 403, B = 427, and Λ = −155 cm−1, respectively.

Characterization of Fine Hydroxyapatite Powders Synthesized by Wet Process

Abstract We prepared fine hydroxyapatite powders by dropping ammonium bi-phosphate into a calcium acetate solution and by vigorously stirring at 3O°C. We measured the powders' specific surface area to be 290 m2/g by the BET technique. The powders were mono-dispersed ultrafine particles by transmission electron microscopy investigation. No phase other than hydroxyapatite (JCPDS: 9–432) was revealed by X-ray diffractometry. A quantitative chemical analysis gave a Ca/P ratio very close to the exact hydroxyapatite stoichiometry (Ca/P: 1.67). Shrinkage started up to 800°C according to a dilatometric measurement and the dense products were obtained when heated at 1000°C for 2 h in air. We used a quadrupole mass spectrometer to monitor the gases desorbed from the hydroxyapatite powders at a constant heating rate of 5°C/min in a high vacuum. It is noted here that there were two peaks of H2O and CO2, respectively, and that we observed an increase in desorption of H2. The two peaks were explained clearly with an in...

The adsorption and decomposition of formic acid on Ni(111): The identification of formic anhydride by vibrational spectroscopy

The adsorption and decomposition of formic acid (HCOOH) on a Ni(111) surface has been examined using thermal desorption spectroscopy (TDS), electron energy-loss spectroscopy (EELS), and reflection–absorption infrared spectroscopy (RAIRS). At 90 K several adsorption states above monolayer coverage are detected. Hydrogen bonding of HCOOH is indicated by strongly red-shifted OH stretching modes. The first layer, possibly consisting of adsorbed HCOOH dimers, is dehydrated above 250 K and forms a stable surface intermediate. Further heating leads to the known autocatalytic decomposition of the surfaces species and produces extremely sharp TDS peaks of CO2 and H2 . Above 360 K only CO is left on the surface. After forming the stable surface intermediate using DCOOH, modes at 776, 1267, 1329, 2181, and 2199 cm−1 are observed by RAIRS. The latter two modes, which are not resolved by EELS, are interpreted as the symmetric and antisymmetric CD stretching modes of the surface intermediate. Consequently, whereas most vibrational studies on other surfaces favor a formate ion (HCOO) as stable surface intermediate, we propose a formic anhydride on the Ni(111) surface. The modes observed at 1323 and 1267 cm−1 are interpreted as symmetric and asymmetric CO stretching modes. The existence of a formic anhydride intermediate is finally confirmed by an experiment using a mixture of HCOOH and DCOOH: The RAIRS spectra show the presence of all three different kinds of intermediates which are (HCO)2 O, (DCO)2 O, and HCO–O–DCO.

Temperature-programmed desorption study of the interactions of H2, CO and CO2 with LaMnO3

Surface interactions of H2, CO and CO2 with the perovskite-type oxide LaMnO3 have been studied by temperature-programmed desorption (t.p.d.) and i.r. spectroscopy. A t.p.d. desorption peak of H2 at 355–360 K, which increases in intensity with increasing reduction temperature of the oxide (Tr), is assigned to molecular adsorption of H2 on reduced manganese sites (Mnn+, n≈ 2). CO adsorption yielded t.p.d. peaks of CO and CO2. A peak of CO at 473 K (for oxidized LaMnO3) associated with a carbonate group and peaks at 360–395 K, 540–550 K and 773–800 K (for reduced LaMnO3) associated with linear and bridged CO species adsorbed on Mnn+ ions were observed. A very wide CO2 desorption peak at 473 K and tail centred at 773 K (oxidized LaMnO3) are associated with monodentate and bidentate carbonates interacting with Mn3+. CO2 adsorption yielded t.p.d. peaks of CO2 at 345–385 K and at 540–665 K whose intensity decreased and increased, respectively, with Tr. These are associated with monodentate and bidentate carbonates, respectively, interacting with reduced sites of manganese or La3+. Detection of bands at ca. 2900 cm–1 in the i.r. spectrum obtained after CO + H2 adsorption, the appearance of new CO desorption features at 570 K and above 860 K, and the detection of a new H2 desorption peak at 770–785 K in the t.p.d. spectra obtained after CO–H2 or H2–CO adsorptions suggest decomposition of an oxygenated species formed by interaction of CO and H2 adsorbed on the same adsorption centre.

Contribution to the residence time of sulfur dioxide in a polluted atmosphere

The atmospheric oxidation of SO2 to SO4= has received much attention because of its importance in atmospheric pollution. In studies on the dispersion of effluents from stacks the oxidation or absorption of sulfur dioxide is of interest, since it shortens the residence time and leads to lower ground level concentrations. Previous measurements have shown that initially the oxidation is quite rapid (almost 30% in about 100 min) for humidities above 70%. In Frankfurt am Main the concentration of air pollutants, wind direction and speed, air temperature, and relative humidity have been continuously recorded for several years. In certain cases short-term peaks (5 to 15 min) of CO2 and SO2 concentrations can be defined as an influence of power station effluents. The CO2 and SO2 concentrations leaving the stack are well known. Carbon dioxide is almost inert, whereas the proportion of sulfur dioxide can decrease by oxidation or absorption while being transported through the atmosphere. In comparison with emissions the air quality measurements in Frankfurt am Main estimate an increased ratio of CO2 to SO2. That is a loss of almost 50% of the total sulfur content in a period of 20 min to 1 hour, depending on meteorological conditions.

Studies on maturation changes in fruits induced by ionizing radiation Part VI

The present paper deals with some observations on the effects of gamma radiation on the changes of respiratory rates, ethylene production, some organic acids, protein and RNA contents during the ripening of Bartlett pears. Irradiation delayed the onset of the respiratory rise and the ethylene production in the climacteric. Control samples required 4 days to reach the peaks of CO2 and C2H4 prodution, respectively. The 250 Krad-fruits required 9 days to reach the peak of CO2 production, and 7 days of C2H4 production. The fruits irradiated with a dose of 1000 Krad showed no increase of CO2 and C2H4 production in climacteric and failed to ripen. Effects of addition of malate on CO2 output of sliced tissue declined in the irradiated samples.The malic and citric acids decreased more in irradiated fruits than in control during ripening. Succinic acid slightly accumulated in the fruits irradiated with a dose of 1000 Krad. The protein N of pears during ripening slightly increased. A dose of 250 Krad, however, suppressed the increasing rate for a few days, followed on the 11th day by recovery to about the level in the control, and there was no recovery in a similar period after irradiation at a dose of 1000 Krad. Total RNA contents of fruits in both the control and the irradiated with a dose of 250 Krad also increased slightly, but it decreased with a dose of 1000 Krad.