Hanna, Sherif Fayez (2005-08). Electronic resonance enhanced coherent anti-Stokes Raman scattering technique for detection of combustion species and biological molecules. Doctoral Dissertation. Thesis uri icon

abstract

  • The application of electronic-resonance enhanced (ERE) coherent anti-Stokes Raman scattering (CARS) for the detection of nitric oxide (NO) and acetylene (C2H2) is experimentally demonstrated and the effects of various parameters on the ERE CARS signal investigated. In addition, the detection of dipicolinic acid (DPA) using ??????normal?????? CARS is demonstrated. For NO detection, the frequency difference between a visible Raman pump beam and Stokes beam is tuned to a vibrational Q-branch Raman resonance of the No molecule to create a Raman polarization in the medium. The second pump beam is tuned into resonance with the rotational transitions in the (1,0) band of the A2????+-X2??? electronic transition at 236 nm, and the CARS signal is thus resonant with transitions in the (0,0) band. A NO gas cell was used for the experiment to detect NO at various pressure levels. A significant resonant enhancement of the NO CARS signal was observed and good agreement between calculated and experimental data was obtained. For C2H2 detection, ERE CARS experiments were performed in a roomtemperature gas cell using mixtures of 5000 ppm C2H2 in N2. Visible pump and Stokes beams were used, with the frequency difference between the pump and Stokes tuned to the 1974 cm-1 ????2 Raman transition of C2H2. An ultraviolet probe beam with the wavelengths ranging from 232 nm to 242 nm is scattered from the induced Raman polarization to generate the ERE CARS signal. The effects of probe wavelength and pressure on signal generation are discussed. CARS was used to detect the 998 cm-1 vibrational Raman transition from a sample of polycrystalline DPA. The transition is the breathing ring vibration in the pyridine ring structure in the DPA molecule. The DPA 998 cm-1 transition is detected with excellent signal-to-noise ratio and the full-width-at-half-maximum is very narrow, approximately 4 cm-1.
  • The application of electronic-resonance enhanced (ERE) coherent anti-Stokes
    Raman scattering (CARS) for the detection of nitric oxide (NO) and acetylene (C2H2) is
    experimentally demonstrated and the effects of various parameters on the ERE CARS
    signal investigated. In addition, the detection of dipicolinic acid (DPA) using ??????normal??????
    CARS is demonstrated.
    For NO detection, the frequency difference between a visible Raman pump beam
    and Stokes beam is tuned to a vibrational Q-branch Raman resonance of the No
    molecule to create a Raman polarization in the medium. The second pump beam is tuned
    into resonance with the rotational transitions in the (1,0) band of the A2????+-X2???
    electronic transition at 236 nm, and the CARS signal is thus resonant with transitions in
    the (0,0) band. A NO gas cell was used for the experiment to detect NO at various
    pressure levels. A significant resonant enhancement of the NO CARS signal was
    observed and good agreement between calculated and experimental data was obtained.
    For C2H2 detection, ERE CARS experiments were performed in a roomtemperature
    gas cell using mixtures of 5000 ppm C2H2 in N2. Visible pump and Stokes beams were used, with the frequency difference between the pump and Stokes tuned to
    the 1974 cm-1 ????2 Raman transition of C2H2. An ultraviolet probe beam with the
    wavelengths ranging from 232 nm to 242 nm is scattered from the induced Raman
    polarization to generate the ERE CARS signal. The effects of probe wavelength and
    pressure on signal generation are discussed.
    CARS was used to detect the 998 cm-1 vibrational Raman transition from a
    sample of polycrystalline DPA. The transition is the breathing ring vibration in the
    pyridine ring structure in the DPA molecule. The DPA 998 cm-1 transition is detected
    with excellent signal-to-noise ratio and the full-width-at-half-maximum is very narrow,
    approximately 4 cm-1.

publication date

  • August 2005