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Formaldehyde reactions in dark clouds
A D Sen1, V G Anicich, S R Federman
1Jet Propulsion Laboratory, California Institute of Technology, Pasadena 91109, USA.
The Astrophysical Journal
|May 20, 1992
Summary
Reactions between formaldehyde and deuterated ions like D+ were studied. Charge transfer dominated, with proton transfer only seen with D3+ ions, near the collision limit.
Area of Science:
- Astrochemistry
- Chemical Kinetics
- Interstellar Medium
Background:
- Formaldehyde (H2CO) is a key molecule in dark interstellar clouds.
- Understanding formaldehyde loss processes is crucial for astrochemistry.
- Deuterated ions serve as experimental analogs for proton reactions.
Purpose of the Study:
- Investigate low-pressure reactions of formaldehyde with D+, D2+, D3+, and He+.
- Determine rate coefficients and product branching ratios for these reactions.
- Assess the significance of these reactions as formaldehyde loss pathways in interstellar clouds.
Main Methods:
- Utilized the ion cyclotron resonance technique.
- Studied reactions at low pressures.
- Measured rate coefficients and branching ratios of product channels.
Main Results:
- Charge transfer was the dominant reaction pathway for H2CO with D+, D2+, and He+.
- Proton transfer was exclusively observed in the reaction of H2CO with D3+.
- All studied reactions occurred at rate coefficients near the collision limit.
- Proton-deuteron exchange reactions were found to be inefficient.
Conclusions:
- These ion-molecule reactions are significant potential loss processes for formaldehyde in interstellar cloud cores.
- The experimental findings provide insights into the chemical evolution of interstellar environments.
- Charge transfer and proton transfer reactions play distinct roles depending on the reactant ion.