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).
$95,218FY2020National Aeronautics and Space AdministrationNASA
University Of Missouri System, Columbia MO