Periodic Reporting for period 3 - HILTRAC (Highly Instrumented Low Temperature Reaction Chamber)
Reporting period: 2023-12-01 to 2025-05-31
With the development of new astronomical tools and telescopes, such as the James Webb Space Telescope and the Atacama Large Millimeter Array (ALMA), there is an abundance of data on the discovery of new molecules and mapping their distribution in the interstellar medium or exoplanetary atmospheres. There is an increasing need for laboratory studies of spectroscopic parameters, chemical reaction rate coefficients in extreme environments, and other associated measurements to support observation and models, to show what chemistry could be present that is currently missing from our understanding, and to suggest where to discover new molecules. The Highly Instrumented Low Temperature Reaction Chamber (HILTRAC) project aims to create a versatile instrument capable of measuring temperature-dependent reaction rate coefficients and branching fractions of astrochemically-relevant gas phase reactions. By using the HILTRAC apparatus, we are studying how seemingly slight changes in chemical composition can result in drastic changes in chemical reactivity and the dynamics of molecular collisions. These changes are inherently linked to the reaction potential energy landscape, which can be experimentally examined by changing the temperature of a chemical reaction and measuring the resulting reaction rate coefficient and product branching ratios.
The HILTRAC apparatus couples a uniform supersonic flow (USF) capable of achieving a wide range of cold temperatures (30 – 150 K) with the unique detection capabilities of an infrared frequency comb spectrometer in addition to the widely accepted detection methodology of laser-induced fluorescence. The work performed thus far started with the design, construction, and characterization of the HILTRAC apparatus with a pulsed Laval nozzle generating the USF. It then moved onto coupling the laser-induced fluorescence detection with the chamber in order to measure temperature-dependent reaction rate coefficients of the CH + OCS reaction. Complementary quantum chemical calculations and reaction kinetics simulations of this reaction has led to insight into the production of HCS under cold temperatures, as discussed further in our recent publication. Work has since moved to incorporating a frequency comb laser with the USF in order to start identifying products from a reaction via their infrared spectroscopic signatures.
The newly built HILTRAC apparatus is one of only a handful in the world capable of generating uniform supersonic flows in which to observe cold chemistry and measure reaction rate coefficients under temperature conditions relevant to the interstellar medium. To the best of my knowledge, it is the first apparatus which couples a frequency comb spectrometer with a pulsed Laval apparatus. We expect to continue to improve the sensitivity of the frequency comb spectrometer, enabling detection and monitoring of reaction products. We also plan to incorporate a mass spectrometer, which will further increase the versatility of the apparatus by expanding the range of chemical reactions for which the apparatus can be used.