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Astrochemistry

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The Savin Group is carrying out laboratory studies of key astrochemical reactions occurring in dense molecular clouds, which give birth to stars and their surrounding planetary systems. Currently, we are studying the formation of H3+ isotopologues such as H2D+ and D2H+. These two molecules trace out the properties of cold, dense gas in prestellar cores and protoplanetary disks, where most other molecules have frozen out, thereby providing important insights into star formation.

The measurements will be performed using the dual-source, merged, fast-beams apparatus that we have used previously to study reactions of neutral atomic C with H3+ (the cosmic origins of organic chemistry) and O with H3+ (leading to gas-phase formation of water in space). With our apparatus we can generate beams of neutral atomic D and react them with H3+ and its isotopologues. Photodetachment of a D- beam will be used to produce a beam of neutral D atoms in their ground state. Beams of H3+ and H2D+ will be generated using a second ion source and various mixtures of H2 and D2. The molecular ions will be electrostatically merged onto the neutral D beam. Merged-beams rate coefficients will be measured covering collision energies of 3.5 meV to 20 eV, the lower limit of which corresponds to a temperature of ~25 K. An electrostatic energy analyzer combined with a channel electron multiplier will be used to detect the daughter product ions of the reactions. Using the known experimental energy spread, cross sections will be extracted and then convolved with a Maxwellian energy spread to generate thermal rate coefficients for molecular cloud temperatures. Measuring all the relevant currents, beam shapes, energies, signal counts, and background rates enables us to generate rate coefficients with an accuracy of ~15%.

REU students working with the Savin Group would be based at Nevis Labs.