Deuterium (d) is one of the light elements created in the big bang, with a primordial abundance (relative to h) of d/h ~ 26PPM. As the galaxy evolves, the d/h ratio in the interstellar medium (ISM)…

This federal contract award, valued at $95,217.69, was granted to the University of Missouri System (doing business as the Curators of the University of Missouri) to conduct research on the infrared emission spectra of deuterated polycyclic aromatic hydrocarbons (PAHs) and their cations. The research aims to support the upcoming James Webb Space Telescope (JWST) mission by providing a computational model and "library" of deuterated PAH spectral data that can be used to quantitatively explore the amount of deuterium locked up in these molecules within the interstellar medium. This work aligns with the Astrophysics Research and Analysis (APRA) program's mission to support fundamental atomic, molecular, and solid-state research that enables the analysis and interpretation of data from NASA astrophysics missions. The award, which does not have a set-aside designation, was granted by the Shared Services Center, a civilian agency within the federal government. The University of Missouri System, a public land-grant research university, is the prime contractor on this grant.

Deuterium (d) is one of the light elements created in the big bang, with a primordial abundance (relative to h) of d/h ~ 26PPM. As the galaxy evolves, the d/h ratio in the interstellar medium (ISM) decreases from its primordial value due to astration , a process which converts d into other elements by nuclear fusion in stellar interiors. However, the observed gas-phase d/h ratios of some sightlines in the local galactic ISM are substantially lower than the expected reduction by astration. The missing d could have been depleted onto polycyclic aromatic hydrocarbon (PAH) molecules which are ubiquitous and abundant in interstellar regions. Pahs of intermediate size are expected to become d enriched in the ISM through the selective loss of h during photodissociation events. When h in pahs is replaced by d, the c-h stretching and bending modes at 3.3, 8.6 and 11.3 micron will shift to longer wavelengths by a factor of the difference in reduced mass between the c-h and c-d oscillators. Therefore, deuterated pahs are expected to emit at ~4.4, 11.7 and 15.4 micron. We propose to compute the infrared emission spectra of deuterated pahs and their cations of various sizes and various degrees of deuteration in a wide range of interstellar regions (e.g., reflection nebulae, photodissocation regions) by making use of the laboratory-measured and quantum-chemically-computed c-d bond strengths of NASA/ames and others together with the stochastical heating model of draine \&LI (2001). The model emission spectra of deuterated pahs will serve as a valuable ``library for jwst whose high sensitivity will revolutionize PAH studies. By comparing our model spectra with the observed spectra obtained by jwst will allow one to quantitatively explore the amount of d/h locked up in pahs, more accurately ever than any previous studies based on ISO, spitzer and akari observations. Our proposed work lies precisely within apra s laboratory astrophysics mission to produce computational efforts to explore the spectroscopic properties of atoms and molecules and particulate matter and support the determination of fundamental atomic, molecular, nuclear and solid-state parameters that are essential for analyzing and interpreting data from NASA astrophysics missions (e.g., jwst).