Radio observations of several interstellar molecules

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1990

OSTI ID:5932184

Minh, Y C

Observations of rotational transitions are presented for several interstellar molecules whose formation may be related to grain processes and their implications are discussed for interstellar chemistry. Instellar hydrogen sulfide was observed at fractional abundances f(H2S) is approximately 10(exp -9) relative to H2 towards cold, dark clouds, while its abundance is enhanced by a factor of 1000 in the Orion hot core and the plateau. H2S may be evaporating from the grain mantles in the hot core, and even in the cold, dark clouds, grain surface reactions may be responsible for the gas-phase H2S abundances. An upper limit was derived for the HDS abundance (HDS)/(H2S) is less than or equal to 6 x 10(exp -4) in the Orion hot core. H2CS ortho-to-para ratios were observed to be approximately 1.8 towards TMC-1, which may suggest that gas-grain exchanges are taking place effectively in cold, dark clouds. A ratio of approximately 3, the statistical value, was derived for Orion (3N1E) and NGC7538, and approximately 2 for Orion (KL). Upper limits were derived for the ethyl cyanide column densities of approximately 3 x 10(exp 12)/sq cm toward TMC-1 and L134N. Together with the detection for vinyl cyanide, there may be no necessity of invoking grain surface synthesis for these highly saturated species in cold clouds. Finally, HOCO+ was surveyed as a tracer of interstellar CO2 towards many galactic sources, and derived f(HOCO+) approximately 10(exp -8) to 10(exp -9) in the Galactic center and less than or equal to 10(exp -10) for cold dark clouds. The observed abundance of HOCO+ in the Galactic center is approximately 3 and approximately 1 orders of magnitude larger than that predicted by ion-molecule chemistry and shock chemistry, respectively.

• Research Organization: Massachusetts Univ., Amherst, MA (USA)
• OSTI ID: 5932184
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
ALKYL RADICALS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHEMISTRY
COSMIC DUST
COSMIC GASES
COSMOCHEMISTRY
CYANIDES
DATA
DECOMPOSITION
DESORPTION
DUSTS
ELEMENTS
ENERGY-LEVEL TRANSITIONS
ETHYL RADICALS
EXPERIMENTAL DATA
FLUIDS
GALAXIES
GASES
HYDROGEN
HYDROGEN COMPOUNDS
HYDROGEN SULFIDES
INFORMATION
NONMETALS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
RADICALS
SULFIDES
SULFUR COMPOUNDS