Christopher F. Neese

6^th year Research Assistant, The University of Chicago

Education

B. A. in Chemistry,
Oberlin College, May 1998.

B. Mus. in TIMARA
(Technology in Music and Related Arts),
Oberlin Conservatory, May 1999.

M. S. in Physical Chemistry,
University of Chicago, August 2000.

Research

Starting in 2000, C. Michael Lindsay and I have incorporated heterodyne detection into our mid-infrared spectrometer.  The spectrometer consists of a Burleigh FCL-20 color center laser, (computer automated in-house), a CdTe electro-optical phase modulator, the sample, and a fast InSb detector.  Combined with a sample modulation scheme (either velocity modulation or concentration modulation), heterodyne detection allows detection with shot-noise-limited sensitivity.

The sample traditionally has been a AC positive column discharge. In the positive column discharge, ions are modulated at the discharge frequency (1–20 kHz), via a process known as velocity modulation. Velocity modulation occurs because ions have a non-zero average velocity proportional to the strength of the electric field, leading to an oscillating Doppler shift. Neutral species maintain a average velocity of zero, and are thus not velocity modulated. Thus, velocity modulation allows the discrimination of ions from neutrals. This is very useful, because the ratio of ions to neutrals is roughly 10^-6.

Recently, we have been bringing a slit-jet discharge on-line.  Due to supersonic expansion, the slit jet expansion is about an order of magnitude colder than a (l)N₂-cooled positive column discharge. Our slit jet discharge is unusual in that it is designed for continuous operation, avoiding the low duty-cycle of pulsed jets.  The discharge can be driven DC or with a 1–100 kHz square wave. The square wave driven discharge will allow us to use concentration modulation with heterodyne detection.

In 2002, our mid-infrared spectrometer was used to record the spectrum of a H₂/He/CH₄/N₂ positive-column discharge.  We have assigned a plethora of new HCNH⁺ hot bands from this discharge. There remain many unassigned ion absorption lines in this spectrum, so we are hopeful that we will find the spectra of some unassigned ions.

In 2004, we recorded hot band of HCO⁺ comparable to those of HCNH⁺ recorded earlier.  These bands were recorded in a H₂/He/CO discharge.  It was also discovered that allene (C₃H₄) in a He discharge produces CH₂⁺ with more selectivity than the He/CH₄ discharges used previously in the Oka group.  We hope to scan this new discharge chemistry with the aim of assigning the K_a ≥ 2 bands of the ν₃ fundamental.

Future projects include studying other carbon-nitrogen discharges and looking for the C₃H₃⁺ ion, which is the simplest aromatic molecule.

Other Interests

Please visit my personal home page.

Publications

• 3 micron Spectroscopy of HCNH⁺ in Highly Excited States.
  Lindsay, C. M.; Neese, C. F.; Oka, T.
  (in preparation).
• 3 micron Hot Bands of HCO⁺.
  Neese, C. F.; Kreynin, P.; Oka, T.
  (in preparation).
• High-resolution spectroscopy of the 2²Π_u ← X⁴Σ_g^- forbidden transitions of C₂⁺.
  Tarsitano, C. G.; Neese, C. F.; Oka, T.
  J. Chem. Phys. 121, 6290-6297 (2004).
• Vibrational Spectroscopy of the Three Isomers of 1,4-Difluorobutadiene.
  Craig, N. C.; Neese, C. F.; Nguyen, T. N.; Oertel, C. M.; Pedraza, L.
  J. Phys. Chem. A. 103, 6726-39 (1999).

Conference Presentations

• High-Resolution Spectroscopy of the  2²Π_u ← X⁴Σ_g^- Forbidden Transitions of C₂⁺.
  Tarsitano, C. G.,  Neese, C. F., and Oka, T.
  Fifty-nineth Ohio State University International Symposium on Molecular Spectroscopy, Columbus, Ohio, June 21-25, 2004.
• High-Resolution Spectroscopy of the  (0,2) and (6,9) bands of the B⁴Σ_u^- ← X⁴Σ_g^- transition of C₂⁺.
  Tarsitano, C. G.,  Neese, C. F., and Oka, T.
  Fifty-eighth Ohio State University International Symposium on Molecular Spectroscopy, Columbus, Ohio, June 16-20, 2003.
• Spectroscopy of Highly Excited HCNH⁺ Using Infrared Heterodyne Velocity Modulation.
  Lindsay, C. M.; Neese, C. F.; Oka, T.
  Fifty-seventh Ohio State University International Symposium on Molecular Spectroscopy, Columbus, Ohio, June 17-21, 2002.
• Infrared Laser Absorbtion Spectroscopy with Heterodyne Detection.
  Lindsay, C. M.; Neese, C. F.; Oka, T.
  Fifty-seventh Ohio State University International Symposium on Molecular Spectroscopy, Columbus, Ohio, June 17-21, 2002.
• Analysis of a C-type Band in the High-resolution Infrared Spectrum of trans,trans-1,4-Difluorobutadiene.
  Craig, N. C.; Neese, C. F.; Oertel, D. C.; Lock, M.
  Fifty-sixth Ohio State University International Symposium on Molecular Spectroscopy, Columbus, Ohio, June 11-15, 2001.
• An Interactive Loomis-wood Package for Spectral Assignment in Igor Pro.
  Neese, C. F.
  Fifty-sixth Ohio State University International Symposium on Molecular Spectroscopy, Columbus, Ohio, June 11-15, 2001.
• Miscellaneous Igor Pro and Excel Add-ins for Spectroscopic Analysis
  Lindsay, C. M.; Neese, C. F.
  Fifty-sixth Ohio State University International Symposium on Molecular Spectroscopy, Columbus, Ohio, June 11-15, 2001.
• Infrared and Raman Spectra of ZE-1,4-Difluorobutadiene.
  Craig, N. C.; Neese, C. F.; Nguyen, T. N.; Oertel, C. M.; Chaka, A. M.
  Fifty-fourth Ohio State University International Symposium on Molecular Spectroscopy, Columbus, Ohio, June 14-18, 1999.

Other Publications

• The High-Resolution Infrared Spectroscopy of the Cyclopropenyl Cation,
  Christopher F. Neese, Doctoral Candidacy Prospectus, (The University of Chicago, October 2000)

Email cfneese@uchicago.edu

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