The elimination of volatile organic compounds (VOCs) from the atmosphere is initiated by reactions with OH, NO₃ and O₃.Atkinson, R.; Arey, J., Chem. Rev. 2003, 103, 4605-4638.^,Mellouki, A.; Le Bras, G.; Sidebottom, H., Chem. Rev. 2003, 103, 5077−5096.or oxygenated VOCs, such as alcohols, ketones, ethers, etc., reactions occur nearly exclusively with the hydroxyl radical. Furthermore, the potential energy surfaces associated with reactions between OH and oxygenated VOCs generally feature a pre−reactive complex, stabilized by hydrogen bonding, which results in rate constants that exhibit large negative temperature dependencies.Smith, I. W. M.; Ravishankara, A. R., J. Phys. Chem. A 2002, 106, 4798−4807his was explicitly demonstrated recently for the OH + methanol (MeOH) reaction, where the rate constant increased by nearly two orders of magnitude when the temperature decreased from 200 K to below 70 K, highlighting the potential impact of this reaction in the interstellar medium (ISM).Shannon, R. J.; Blitz, M. A.; Goddard, A.; Heard, D. E., Nat. Chem. 2013, 5, 745−749.^,Martin, J. C. G.; Caravan, R. L.; Blitz, M. A.; Heard, D. E.; Plane, J. M. C., J. Phys. Chem. A 2014, 118, 2693-2701.n this study, we trap this postulated pre-reactive complex formed between OH and MeOH using He nanodroplet isolation (HENDI) techniques, and probe this species using a combination of mass spectrometry and infrared laser Stark spectroscopy.

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Footnotes:

Atkinson, R.; Arey, J., Chem. Rev. 2003, 103, 4605-4638.\end Mellouki, A.; Le Bras, G.; Sidebottom, H., Chem. Rev. 2003, 103, 5077−5096.F\end Smith, I. W. M.; Ravishankara, A. R., J. Phys. Chem. A 2002, 106, 4798−4807T\end Shannon, R. J.; Blitz, M. A.; Goddard, A.; Heard, D. E., Nat. Chem. 2013, 5, 745−749. Martin, J. C. G.; Caravan, R. L.; Blitz, M. A.; Heard, D. E.; Plane, J. M. C., J. Phys. Chem. A 2014, 118, 2693-2701.I

l0pt Figure Carbohydrates are one of the most multifaceted building blocks, performing numerous roles in living organisms. We present several structural investigations on carbohydrates exploiting an experimental strategy which combines microwave (MW) and laser spectroscopies in high-resolution. Laser spectroscopy offers high sensitivity coupled to mass and conformer selectivity, making it ideal for polysaccharides studies. On the other hand, microwave spectroscopy provides much higher resolution and direct access to molecular structure of monosaccharides. This combined approach provides not only accurate chemical insight on conformation, structure and molecular properties, but also benchmarking standards guiding the development of theoretical calculations. In order to illustrate the possibilities of a combined MW-laser approach we present results on the conformational landscape and structural properties of several monosaccharidesE.J. Cocinero, A. Lesarri, P. Écija, F.J. Basterretxea, J.-U. Grabow, J.A. Fernández and F. Castaño Angew. Chem. Int. Ed. 51, 3119-3124, 2012.^,E.J. Cocinero, A. Lesarri, P. Écija, Á. Cimas, B.G. Davis, F.J. Basterretxea, J.A. Fernández and F. Castaño J. Am. Chem. Soc. 135, 2845−2852, 2013.nd oligosaccharides including microsolvation and molecular recognition processes of carbohydrates.E.J. Cocinero, P. Çarçabal, T.D. Vaden, J.P. Simons and B.G. Davis Nature 469, 76−80, 2011.^,C.S. Barry, E.J. Cocinero, P. Çarçabal, D.P. Gamblin, E.C. Stanca-Kaposta, S. M. Fernández-Alonso, S. Rudi\'c, J.P. Simons and B.G. Davis J. Am. Chem. Soc. 135, 16895-16903, 2013.html:<hr /><h3>Footnotes: E.J. Cocinero, A. Lesarri, P. Écija, F.J. Basterretxea, J.-U. Grabow, J.A. Fernández and F. Castaño Angew. Chem. Int. Ed. 51, 3119-3124, 2012.\end E.J. Cocinero, A. Lesarri, P. Écija, Á. Cimas, B.G. Davis, F.J. Basterretxea, J.A. Fernández and F. Castaño J. Am. Chem. Soc. 135, 2845−2852, 2013.a\end E.J. Cocinero, P. Çarçabal, T.D. Vaden, J.P. Simons and B.G. Davis Nature 469, 76−80, 2011. C.S. Barry, E.J. Cocinero, P. Çarçabal, D.P. Gamblin, E.C. Stanca-Kaposta, S. M. Fernández-Alonso, S. Rudi\'c, J.P. Simons and B.G. Davis J. Am. Chem. Soc. 135, 16895-16903, 2013.

Accurate potential energy surfaces (PESs) combined with methods to solve the Schrödinger equation for the nuclei permit the prediction and interpretation of various types of molecular spectra and/or dynamics. Part of this talk describes the development of a PES generator (software code) which uses parallel processing on High-Performance Computing (HPC) clusters to construct PESs automatically. Thousands of ab initio data are computed at geometries chosen by an algorithm and fit to a functional form. This strategy is particularly successful when the electronic structure is robustly convergent (such as vdWs systems composed of two closed-shell monomers). Results for a few of such systems [e.g., (CO)₂, (NNO)₂, CO₂-CS₂, (OCS)₂] will be presented. The electronic structure of molecules is difficult to describe continuously across global reactive PESs since it changes qualitatively as bonds are formed and broken along reaction coordinates. I will discuss a high-level ab initio method (GDW-SA-CASSCF/MRCI) designed to allow the electronic wavefunction to smoothly evolve across the PES and provide an accurate and balanced description of the various regions. These methods are combined to study a number of small gas-phased molecules from the areas of atmospheric, combustion and interstellar chemistry including a large variational calculation of all the bound vibrational states of ozone and the photodissociation dynamics of the simplest Criegee intermediate (CH₂OO).

While both the number of detected interstellar molecules and their chemical complexity continue to increase, understanding of the processes leading to their formation is lacking. Our research group combines laboratory spectroscopy, observational astronomy, and astrochemical modeling for an interdisciplinary examination of the chemistry of star and planet formation. This talk will focus on our laboratory studies of O(¹D) insertion reactions with organic molecules to produce molecules of astrophysical interest. By employing these reactions in a supersonic expansion, we are able to produce interstellar organic reaction intermediates that are unstable under terrestrial conditions; we then probe the products using millimeter and submillimeter spectroscopy. We benchmarked this setup using the well-studied O(¹D) + methane reaction to form methanol. After optimizing methanol production, we moved on to study the O(¹D) + ethylene reaction to form vinyl alcohol (CH₂CHOH), and the O(¹D) + methyl amine reaction to form aminomethanol (NH₂CH₂OH). Vinyl alcohol measurements have now been extended up to 450 GHz, and the associated spectral analysis is complete. A possible detection of aminomethanol has also been made, and continued spectral studies and analysis are underway. We will present the results from these experiments and discuss future applications of these molecular and spectroscopic techniques.

The JPL molecular spectroscopy group supports NASA programs encompassing Astrophysics, Atmospheric Science, and Planetary Science. Ongoing activities include measurement and analysis of molecular spectra in the terahertz and infrared regions under conditions akin to the remote environments under study in NASA missions. This presentation will show the implementation of state-of-the-art spectroscopic techniques to fulfill spectroscopic demands of the Herschel Space ObservatoryG. Pilbratt, J. Riedinger, T. Passvogel, G. Crone, D. Doyle, U. Gageur et al. A&A, 518, L1 (2010).nd the Orbiting Carbon Observatory re-flight (OCO-2)D. Crisp, B.M Fisher, C. O'Dell, C. Frankenberg, R. Basilio, H. Boesch et al., Atmos. Meas. Tech. 5, 687-707 (2012). A demonstrative example of the significantly improved frequency predictions for the H₃O⁺ ground state high-J transitions will be given. This work was critical to Herschel's successful identification of highly excited metastable H₃O⁺ Terahertz lines with J=K up to 11, one of the Herschel mission's many surprising observational results. The observation and subsequent laboratory work revealed that (1) these highly excited H₃O⁺ lines had already been observed by European Southern Observatory's Atacama Pathfinder Experiment telescope a few years before but had been classified as U-lines; (2) the H₃O⁺ number density was previously underestimated by an order of magnitude, due to ignorance of the population in the metastable states. A second example focuses on O₂, an important absorber from the microwave through the deep UV. This work is motivated by the challenge of developing an accurate and complete spectroscopic characterization of molecular oxygen across a wide frequency range for current and planned Earth atmospheric observations. Especially, OCO-2 utilizes the O₂ A-band for air mass calibration; extremely accurate O₂ molecular data, i.e., line positions with uncertainty on the order of MHz for the A-band around 13000 cm⁻¹, are required to fulfill the demand of the proposed 0.25% precision for the carbon dioxide concentration retrievals.

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Footnotes:

G. Pilbratt, J. Riedinger, T. Passvogel, G. Crone, D. Doyle, U. Gageur et al. A&A, 518, L1 (2010).a D. Crisp, B.M Fisher, C. O'Dell, C. Frankenberg, R. Basilio, H. Boesch et al., Atmos. Meas. Tech. 5, 687-707 (2012)..

r0pt Figure The first beam of helium droplets was reported in the 1961 paper Strahlen aus kondensiertem Helium im Hochvakuum by Von E. W. Becker and co-workers.E. W. Becker, R. Klingelhöfer, P. Lohse, Z. Naturforsch. A 16A, 1259 (1961).owever, molecular spectroscopy of helium-solvated dopants wasn't realized until 30 years later in the laboratories of Scoles and Toennies.S. Goyal, D. L. Schutt, G. Scoles, Phys. Rev. Lett. 69, 933 (1992).^, M. Hartmann, R. E. Miller, J. P. Toennies, A. F. Vilesov, Phys. Rev. Lett. 75, 1566(1995).I