Laboratory Measurements of Dissociative Recombination with Cold Molecular Ions for Ground-Based Studies of Diffuse Molecular Clouds

Dissociative recombination (DR) with electrons is the dominant process by which molecular ions are destroyed in the diffuse interstellar medium. This research project will determine the rates of DR reactions of three molecular ions CF+, CH+, and SH+ in the laboratory at low temperatures and pressures that simulate the conditions in space. Rates from the study will allow astronomers to infer accurate abundances of these ions and use them as probes of the physics and chemistry of the interstellar gas. The project will support the training of a postdoctoral scholar and provide research opportunities to an undergraduate student.

The research team will perform the laboratory DR measurements using the Cryogenic Storage Ring (CSR) located at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. The CSR can store ions for over 1,000 seconds, allowing them to cool radiatively to low rotational energy levels comparable to those in diffuse molecular clouds. Using the DR measurements, the team will generate accurate thermal rate coefficients at low temperatures relevant to diffuse clouds. Reliable DR data from the project will enable astronomers to use CF+, CH+, and SH+ abundances to probe key properties and processes in the diffuse gas.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.