Jennifer L. Gottfried

5th year Research Assistant,
The University of Chicago
Curriculum Vitae

Education

Ph.D. in Physical Chemistry,

Expected Graduation August 2005.

M.S. in Physical Chemistry,
University of Chicago, August 2001.

B.S. in Chemistry w/minors in Mathematics and Physics,
Ohio Northern University, May 2000.

Research

We are studying molecular ions of astronomical and theoretical interest via high-resolution near-infrared spectroscopy.  To this aim, a highly sensitive spectrometer based on Verdi-pumped Ti:sapphire ring laser was recently developed using a variety of techniques: velocity modulation,¹ multipassing (a modified White cell configuration),  noise subtraction, and frequency modulation.²  Custom software has been written to improve the computer control of the laser and to facilitate the data acquisition process.  With this system, we have successfully identified new spectra of H₃⁺ and CH₂⁺.

As the simplest polyatomic molecule, H₃⁺ serves as a benchmark for the theoretical calculation of rovibrational energy levels of polyatomic molecules. This interesting and unique molecule has been studied in the Oka Ion Factory for many years, since the first detection of its infrared spectrum in 1980.³   The laboratory spectroscopy of H₃⁺ is of both astronomical and theoretical interest.  With the aid of spectroscopic data, astronomical observations have revealed the presence of  H₃⁺ in the interstellar medium⁴ and in planetary ionospheres.  We have observed the first H₃⁺ transitions above the barrier to linearity (the energy regime in which H₃⁺ has enough energy to sample linear configurations).  Experimentally determined energy levels provide a critical test of ab initio calculations in this challenging regime (>10,000 cm^-1).  Although the high energy levels in this work are considerably above the highest levels observed thus far in astronomical plasmas, they may be observable in Jupiter's ionosphere and other high-temperature astronomical objects in the near future.

Our most recent work involves the observation of the near-infrared spectrum of CH₂⁺.  The molecular ion CH₂⁺ is of special interest because of its quasilinearity and the strong interaction of its ground and first excited states due to the Renner-Teller effect.  At linearity the ground state is a doubly degenerate ²P_u state that splits into X²A₁ and A²B₁ states as the molecule bends.  In the ground state the molecule is a near-prolate asymmetric rotor (ŠHCH=140°), but the excited state equilibrium geometry is linear.  Although the initial detection of the infrared spectrum of the n₃ band⁵ confirmed the bent nature of CH₂⁺ in the ground state, this work presents the first experimental spectroscopic characterization of the A²B₁ state.  We have observed  five new absorption bands of CH₂⁺ — four of these bands have been assigned thus far.

* This material is based upon work supported under a National Science Foundation Graduate Research Fellowship.
 

¹ C.S. Gudeman, M.H. Begemann, J. Pfaff, and R.J. Saykally, Phys. Rev. Lett. 50, 727 (1983).
² G.C. Bjorklund, Opt. Lett. 5, 15 (1980).
³ T. Oka, Phys. Rev. Lett. 45, 531 (1980).

⁴ T.R. Geballe and T. Oka, Nature 384, 334 (1996)

⁵ M. Rösslein, C.M. Gabrys, M.-F. Jagod, and T. Oka, J. Mol. Spectrosc. 153, 738 (1992).

 
Publications

Conference Presentations

Other Documents