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 âÂÂnormalâÂÂ
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 A2ã+-X2ÃÂ
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 ÃÂ
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.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4379 |
| Date | 30 October 2006 |
| Creators | Hanna, Sherif Fayez |
| Contributors | Caton, Jerald A., Lucht, Robert P. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 4452031 bytes, electronic, application/pdf, born digital |
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