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Session 20 - Chemistry & Physical Process in the ISM.
Display session, Wednesday, January 07
Exhibit Hall,

[20.07] Detection of Alfvén Waves by Molecular Spectroscopy - Deuterium Chemistry

H. M. Butner (SMTO), S. B. Charnley (NASA/ARC)

Hydromagnetic waves could be a major source of line broadening in molecular clouds. They are also important in transporting angular momemtum during gravitational collapse. Ambipolar diffusion between ions and neutrals determines the loss of magnetic flux from magnetically supported clumps of gas and thus plays a critical role in the initial stages of low mass star formation . However, direct evidence of hydromagnetic waves or the presence of ambipolar diffusion is difficult to obtain. Charnley (1997) presents one possible method of detecting hydromagnetic waves by their effect on molecular chemistry. Ion-neutral streaming, induced by the passage of a hydromagnetic wave, can affect the molecular chemistry by driving some endothermic reactions at enhanced rates.

We have examined a number of deuterated species in several molecular clouds, looking for evidence of both abundance variations and velocity fields consistent with the predictions of the Charnley model. Deuterated species were chosen because they have small temperature barriers in their formation. The low-amplitude Alfvén waves considered by Charnley (1997) have low drift speeds, but still high enough to drive deuterium fractionation chemistry.

We report on our initial observations, done with the NRAO 12 meter telescope. We studied a number of deuterated molecules. We discuss how the observations compare with the model predictions of Charnley (1997). In particular, we examine how the deuterium fractionation and velocity field change as a function of location in the clouds studied.

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