The research in the Dodson group uses new and existing spectroscopic and kinetic tools to study chemical reactions occurring at low temperatures (< 50 K), with direct application to understanding chemistry as it occurs in space and other cold environments. These low-temperature techniques enable the detection and study of exotic and often highly unstable molecules, yielding previously undiscovered chemical insights into reaction mechanisms.

Check out the group twitter account or Prof. Dodson’s Google Scholar profile.

Spectroscopic Studies of Intermolecular Interactions

Low-temperature environments provide the energetic conditions necessary to study weak molecule/molecule and molecule/surface binding interactions. Our group studies the interactions of small molecules in matrix environments—using primarily experimental (infrared spectroscopy) techniques supported by theoretical (quantum chemistry) analysis—probing those interactions directly [1] and exposing how the environment may perturb the structure of isolated molecules [2]. Our group also studies the interactions between adsorbed small molecules and porous materials at low temperatures and is using these materials as a means to study and promote the enrichment of nuclear-spin isomers.

Mass Spectrometry Techniques for Reaction Kinetic

Our group is developing custom mass spectrometry tools to study ion/molecule reactions that uniquely occur in low-temperature, low-pressure environments. Of interest are radiative association reactions, which are important in interstellar chemistry but can generally only be studied under specialized laboratory conditions that minimize competitive three-body interactions. Such reactions generally cannot be modeled by standard Arrhenius kinetics, so these reactions must be carried out under controlled temperatures relevant to space. Our instrumentation is tailor-made to study the formation of organometallic molecules via such reactions. We also collaborate with scientists at DOE labs to use tunable synchrotron radiation and multiplexed photoionization mass spectrometry to carry out reaction kinetics experiments that quantitatively probe the fate of astrochemically relevant species. [3]

Cavity-Enhanced Spectroscopy of Buffer-Gas Cooled Molecules

In order to carry out kinetic studies of reactions proceeding at low temperature, it is necessary to quantify the temperature of reactant molecules, here meaning not only their translational temperature but also vibrational and rotational temperature. We use buffer-gas cooling techniques as our primary method for producing cold molecules, which we couple to high-sensitivity, high-resolution cavity-enhanced techniques to probe the rotationally resolved Doppler-broadened spectra. These measurements empower us to have excellent control in preparing our reactant molecules, ensuring the accuracy of our kinetic measurements. We are also generally interested in understanding and improving the technology available for buffer-gas cooling, as it is a broadly applicable tool for producing a wide range of cold molecules in the gas phase.

References

[1] Hockey, E. K., Vlahos, K., Howard, T., Palko, J., Dodson, L. G. “Weakly bound complex formation between HCN and CH3Cl: A matrix-isolation and computational study,” J. Phys. Chem. A, 2022, 126, 3110 – 3123.DOI:10.1021/acs.jpca.2c00716

[2] Hockey, E. K., McLane, N., Vlahos, K., McCaslin, L. M., Dodson, L. G. “Matrix-formation dynamics dictate methyl nitrite conformer abundance,” ChemRxiv DOI: 10.26434/chemrxiv- 2023-4vtc9).J. Chem. Phys, 2024, 160, 094303. DOI:
10.1063/5.0188433

[3] Hockey, E. K., McLane, N., Martí, C., Duckett, L., Osborn, D. L., Dodson, L. G. “Direct
observation of gas-phase hydroxymethylene: Photoionization and kinetics resulting from
methanol photodissociation,” J. Am. Chem. Soc., 2024, 146, 14416 – 14421. DOI:
10.1021/jacs.4c03090