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Mitchell, G. F.

Publications and source records attributed to Mitchell, G. F..

9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

The detection of a discrete outflow from the young stellar object GL 490

A high-resolution (0.059/cm) M-band spectrum has been obtained of the embedded young stellar object GL490. The spectrum shows interstellar absorption in the fundamental vibrational band, v = 1-0, of (C-12)O. Two strong and narrow (10 km/s) velocity components are present. One, at the velocity of GL490 (vLSR = -16 km/s), is likely gas in the molecular cloud within which GL490 is embedded. The other component is blueshifted by 13 km/s relative to GL490. An observation of emission from the J = 3-2 transition of HCO(+) using a 20-arcsec beam supports the view that the blueshifted gas is near the central object. The -29-km/s feature is interpreted as a recently ejected shell. It is conjectured that the extended outflows of cold molecular gas seen by millimeter CO emission observations are driven by sporadic outbursts rather than by continuous flows from the central object.

Mitchell, G. F.↗
NASA NTRS1982

A CO2-rich coma model applied to the neutral coma of Comet West

Models of the cometary coma in which the dominant volatile is CO2 have been constructed for a range of heliocentric distances. Model coma abundances of C2, C3, and CN are compared with the abundances observed in Comet West and are found to be in good agreement. Furthermore, the variation with heliocentric distance of C2, C3, and CN model abundances agree well with the observed variation in Comet West. The present work lends detailed support to a previous suggestion that a substance more volatile than water, such as CO2, controls the evaporation of the nucleus of Comet West. The implications for cometary formation are briefly discussed.

Mitchell, G. F.↗
NASA NTRS1980

Laboratory and modeling studies of chemistry in dense molecular clouds

A chemical evolutionary model with a large number of species and a large chemical library is used to examine the principal chemical processes in interstellar clouds. Simple chemical equilibrium arguments show the potential for synthesis of very complex organic species by ion-molecule radiative association reactions.

Huntress, W. T., Jr.↗
NASA NTRS1979

Interstellar synthesis of the cyanopolyynes and related molecules

The cyanopolyynes HC2CN, HC4CN, HC6CN, and HC8CN, and the molecules CH3CHCN and CH3CH2CN, have recently been detected in the interstellar medium. It is shown that the observed abundances of these molecules can be obtained by gas-phase formation pathways if the reaction of H2CN(+) with C2H2 is rapid at low interstellar temperatures. The molecules CH2CHCN and C3N may be formed also by the reactions of H2CN(+) with C2H2, and CH3CH2CN may be formed by reaction of H2CN(+) with C2H4.

Mitchell, G. F.↗
NASA NTRS1979

The synthesis of complex molecules in interstellar clouds

The abundances of polyatomic molecules that may be formed by CH3(+) radiative association reactions in dense interstellar molecular clouds are reevaluated. The formation of a number of complex interstellar molecules via radiative association reactions involving ionic precursors other than CH3(+) is also investigated; these additional precursors include CH3O(+), CH3CO(+), CH5(+), HCO(+), NO(+), H2CN(+), C2H2(+), and NH3(+). The results indicate that the postulated gas-phase ion-molecule radiative association reactions could potentially explain the synthesis of most of the more complex species observed in dense molecular clouds such as Sgr B2. It is concluded, however, that in order to be conclusive, laboratory data are needed to show whether or not these reactions proceed at the required rates at low temperatures.

Huntress, W. T., Jr.↗
NASA NTRS1979

Long chain carbon molecules and diffuse interstellar lines

An estimate of the abundances of chain hydrocarbon molecules expected in dense interstellar clouds as a result of gas-phase chemistry alone supports the hypothesis that the long chain molecules are responsible for the diffuse interstellar lines seen in the optical spectra of stars lying behind fairly low-density interstellar clouds. In particular, it is shown that the equilibrium abundances of the long chain carbon molecules may remain quite high even for molecules with as many as 11 carbon atoms.

Mitchell, G. F.↗