Cars temperature measurements and stability studies of a d. c. nitrogen discharge. Final report, September 1989-July 1991. [CARS (coherent anti-Stokes Raman spectroscopy)]

Technical Report · Mon Jul 01 04:00:00 EDT 1991

OSTI ID:5934944

Millard, M

The vibrational and rotational temperatures of a 30-Torr, normal glow N2 gas discharge have been measured using a coherent anti-Stokes Raman spectroscopy system in the folded BOXCARS configuration. The discharge was set up in slowly flowing nitrogen between two plane parallel molybdenum electrodes. Current densities of O.047 A/sq cm were used with an E/N of approximately 50 Td. The nearly wall-less discharge was stabilized using a Macor ceramic cap covering the cathode with a 9-mm circular aperture in the center. Measurements were made at spatially resolved locations within the discharge both axially and radially. Theoretical spectra were fit to experimental data in order to obtain the rotational and vibrational temperatures and the relative populations. A detailed study of the spectral line shape of the dye laser used as the probe beam in the CARS system was carried out using the optogalvanic effect in a Fe-Ne hollow-cathode lamp. The spectral line width and lineshape under differing dye pumping schemes were obtained. These measured line widths were greater than expected and showed a non-Gaussian profile for the probe laser. Stability of the nitrogen discharge was also studied in order to determine the conditions under which the discharge remains stable. Instability was noted visually, in the behavior of the CARS signal and the electrode voltage, both of which showed hysteresis. In order to make way for changes in the system in the future, a new CARS system was designed which will allow study of various gasses under differing discharge conditions.

• Research Organization: Dayton Univ., OH (United States). School of Engineering
• OSTI ID: 5934944
• Report Number(s): AD-A-268530/3/XAB; CNN: F33615-81-C-2012
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102* -- Chemical & Spectral Procedures
664000 -- Atomic & Molecular Physics-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
DATA
ELECTRIC DISCHARGES
ELEMENTS
ENERGY LEVELS
EXCITED STATES
EXPERIMENTAL DATA
GLOW DISCHARGES
HYSTERESIS
INFORMATION
LASER SPECTROSCOPY
LINE WIDTHS
NITROGEN
NONMETALS
NUMERICAL DATA
RAMAN SPECTRA
RAMAN SPECTROSCOPY
ROTATIONAL STATES
SPECTRA
SPECTROSCOPY
STABILITY
VIBRATIONAL STATES