No abstract

No abstract

formate structure is seen to develop to approximately the same extent as on clean A1203. A likely site for formate production is therefore an oxygen center that is left exposed during dehydroxylation of the A1203 surface.CA. P.B. is grateful for a supported educational leave from Alcoa.

Infrared spectra of H2O + CO2 and H2O + CO ices before and after proton irradiation showed that a major reaction in both mixtures was the interconversion of CO2 ⇌ CO. Radiation synthesized organic compounds such as carbonic acid were identified in the H2O + CO2 ice. Different chemical pathways dominate in the H2O + CO ice in which formaldehyde, methanol, ethanol, and methane were identified. Sublimed material was also analyzed using a mass spectrometer. Implications of these results are discussed in reference to comets.

Experimental studies of the vapor phase nucleation of refractory compounds. V. The condensation of lithium

No abstract

Under conditions in the primordial solar nebula and dense interstellar clouds, small grains have low relative velocities. This is the condition for efficient sticking and formation of fractal aggregates. A calculation of the ratio of cross-section, a, to number of primary particles, N, for fractal clusters yielded In a/N = 0.2635 + 0.5189N (-°'x74s). This ratio decreases slowly with N and approaches a constant for large N. Under the usual assumption of collisions producing spherical compact, uniform density aggregates, a/N varies as N-1/3 and decreases rapidly. Fractal grains are therefore much more closely coupled to the gas than are compact aggregates. This has a significant effect on the aerodynamic behavior of aggregates and consequently on their evolution and that of the nebula.

No abstract