Nadine Wehres

Postdoctoral Scholar

Emory University

Office: 131 Atwood Hall

1515 Dickey Drive

Atlanta, GA 30322-2210

phone: 404-727-6573

fax: 404-727-6586

Educational Background

Diplom (M.S.) in Physical Chemistry from Heinrich Heine University, Dusseldorf, Germany (2006)
Ph.D. in Astrophysics from Kapteyn Astronomical Institute, Rijksuniversity Groningen, The Netherlands (2011)
Postdoctoral Researcher at the Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, USA (2013)
Postdoctoral Researcher in Physical Chemistry, Emory University

Current Research

I am interested in the overlap between laboratory astrophysics (laser spectroscopy) and observational astronomy. Knowledge of the molecular constituents of different interstellar environments gives hint on the physical and chemical conditions that occur in that particular environment. For example: identification of a molecular signature in the laboratory or in space gives us immediate access to temperatures, densities and abundances of that particular molecule. Molecules in turn have direct influence on the chemistry and physics in their environment. They are important for the heating and cooling mechanisms that ultimately drive star and planet formation. Eventually molecules are the building blocks of life.

During my Ph.D., I studied UV / VIS spectra of molecules that I created in a pulsed plasma discharge. Subsequent cooling in a molecular beam expansion can give access to electronically excited states of molecules that nonetheless are rotationally rather cold. I was looking for transient species, like carbon chains and hydrocarbon chains, molecules of astrophysical interest, which are highly unstable under normal terrestrial conditions. I recorded cavity ring-down and laser induced fluorescence spectra and compared those to optical spectra that I obtained from telescopes. The cavity ring-down absorption spectra were compared to diffuse interstellar clouds, which show a plethora of unidentified absorption lines, known as the "diffuse interstellar bands". Fluorescence spectra obtained in the lab were compared to emission spectra of the Red Rectangle proto-planetary nebula.

As a postdoctoral researcher at the Center for Astrophysics and Space Astronomy at the University of Colorado, Boulder, I worked in the overlap of observational astronomy and laboratory astrochemistry. I studied UV, VIS and near-IR spectra of diffuse interstellar clouds, as well as the Red Square nebula. We determined temperatures, densities and abundances of molecules in different interstellar environments. In the laboratory I studied ion-molecule reactions of interstellar interest to determine reaction rates and branching ratios for the formation and destruction of interstellar molecules.

Here in Emory I will be extending my knowledge of high-resolution spectroscopy into the lower frequency regime. Specifically, I will record laboratory spectra in the millimeter / Submillimeter and THz regime. The focus is on protonated clusters that will be produced using a Hollow Cathode Discharge. The laboratory spectra will be compared to CSO observational line surveys. These line surveys have previously been recorded in our group and are currently being analyzed. With this approach we hope to shed light on the molecular inventory of hot cores, their physical and chemical conditions, and chemical reaction networks.

Refereed Publications

  • Wehres N., Cross T., Radhuber M. L., Zou L., Carroll A. and Widicus Weaver S. L., "A Hollow Cathode THz Spectrometer for the Study of Astrophysical Ions and Radicals: Benchmarking with N2H+ and Extended Measurements for N2D+." J. Mol. Spectrosc. , 306, 1-5, 2014. (View Paper)
  • N. Wehres, B. Ochsendorf, J. Bally, T.P. Snow, V.M. Bierbaum, N. Cox, L. Kaper and A.G.G.M. Tielens,"Search for DIBs in Emission: MWC 922 - The Red Square Nebula", The Diffuse Interstellar Bands, Proceedings of the International Astronomical Union, IAU Symposium, 297, 226 (2014).
  • Z. Lin, D. Talbi, E. Roueff, E. Herbst, N. Wehres, C.C. Cole, Z. Yang, T.P. Snow and V.M. Bierbaum,"Can Interstellar Propene (CH3CHCH2) be formed via Gas-Phase Reactions?", Astrophysical Journal Letters, 765, L80 (2013).
  • J.M. Garver, Z. Yang, N. Wehres, C.M. Nichols, B.B. Worker and V.M. Bierbaum,"The α-effect in elimination reactions and competing mechanisms in the gas phase", International Journal of Mass Spectrometry , 330, 182 (2012).
  • C.A. Cole, N. Wehres, Z. Yang, D.L. Thomsen, T.P. Snow and V.M. Bierbaum,"A Gas-Phase Formation Route to Interstellar Trans-methyl formate", Astrophysical Journal Letters , 745, L5 (2012).
  • N.J. Demarais, Z. Yang, O. Martinez, N. Wehres, T.P. Snow and V.M. Bierbaum,"Gas-phase Reactions of Polycyclic Aromatic Hydrocarbon Anions with Molecules of Interstellar Relevance", Astrophysical Journal , 746, 32 (2012).
  • N. Wehres, H. Linnartz, H. Van Winckel and A.G.G.M. Tielens,"The offset dependent behavior of the narrow optical emission features in the Red Rectangle proto-planetary nebula", Astronomy & Astrophysics , 533, A28 (2011).
  • D. Zhao, N, Wehres, W. Ubachs and H. Linnartz,"Electronic Spectra and Molecular Geometry of the non-linear carbon chain C9H3", Chemical Physics Letters , 501, 232 (2011).
    • N. Wehres, H. Van Winckel, H. Linnartz and A.G.G.M. Tielens,"C2 emission features in the Red Rectangle proto-planetary nebula - a combined/observational study", Astronomy & Astrophysics , 518, A36 (2010).
    • N. Wehres, D. Zhao, W. Ubachs and H. Linnartz,"Rotationally resolved A3Σu- - X3Σg- spectrum of HC7H", Chemical Physics Letters , 497, 30 (2010).
    • H. Linnartz, N. Wehres, H. Van Winckel, G.A.H. Walker, D.A: Bohlender, A.G.G.M. Tielens, T. Motylewski and J.P. Maier,"A coincidence between a hydrocarbon plasma absorption spectrum and the #lambda 5450 DIB", Astronomy & Astrophysics , 511, L3 (2010).
    • E.A. Volkers, J. Bulthuis, S.Stolte, R. Jost, N. Wehres and H. Linnartz, "Vibronic spectrum of 15N16O2 between 415 and 440 nm", Journal of Molecular Spectroscopy , 245, 1 (2007).
    • B.F. Parsons, S.H. Sheehan. T.A. Yen, D.M. Neumark, N. Wehres, R. Weinkauf, "Anion photoelectron imaging of deprotonated Thymine and Cytosine", Physical Chemistry Chemical Physics , 9, 3291 (2007).
    • S.M. Sheehan, G. Meloni, B.F. Parsons, N. Wehres and D.M Neumark, "Spectroscopic characterization of the ground and low-lying electronic states of Ga2N via anion-photoelectron spectroscopy", Journal of Chemical Physics , 124, 4303 (2006).