Detection of atomic oxygen and hydrogen by resonance fluorescence in the vacuum UV using a Raman-shifted dye laser
Laser-induced fluorescence has been used for the measurement of particle densities and velocity distributions in many different situations, such as in thermonuclear or sputtering devices, glow discharges and flames. The detection of metal atoms is relatively easy to perform, since their resonance lines are in the visible or near UV, and the fundamental frequency of a dye laser or its second harmonic produced in a crystal is sufficient to excite the fluorescence. However, the light atoms H, C, N and O have their resonance lines in the vacuum UV, and more elaborate methods for frequency shifting are needed. With a frequency-doubled dye laser, continuously tunable radiation down to at least 1215 Angstroms (L(alpha)) can be produced by stimulated Raman scattering with two different dyes. The main drawback of Raman-shifting of the dye laser is obviously the high amplitude fluctuation, which can reach more than +/- 50%, whereas the fluctuations can be reduced to less than +/- 10% with a frequency-tripled laser. However, averaging over a sufficient number of shots can also lead to reproducible results (+/- 10%) in the case of Raman shifting. This method enables fluorescence experiments on atomic hydrogen and oxygen.
Bibliographic Reference: Article: Proceedings of the 5th International Symposium on Laser-Aided Plasma Diagnostics (1991) pp. 30-35
Record Number: 199111653 / Last updated on: 1994-12-02
Original language: en
Available languages: en