Narrow-linewidth ultraviolet source for Rayleigh and Raman applications
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A pulsed, high-efficiency, narrow-linewidth ultraviolet source is developed to explore its potential for Rayleigh and Raman applications. A mercury lamp is driven with a high-voltage (30-kV), 2-ns-long, high-repetition-rate pulse supply that produces a high average power train of light pulses. Each pulse in the train has a time-varying spectrum that narrows to a single spectral line after 100 ns or so. This ultranarrow line output falls at 254 nm and lends itself to filtered Rayleigh and filtered Raman scattering measurements in conjunction with a mercury vapor filter. The performance of the mercury lamp has been characterized by operating the lamp in different configurations and at various operating conditions. It was found that the lamp with the external electrodes performs better than that with inner electrodes. The possibility of obtaining other Hg-UV lines, particularly 185-nm radiation, has also been explored. The suitability of this lamp for Raman measurements has been tested by recording vibrational Raman spectrum for methanol. Filtered Rayleigh signals were also obtained for CO2at various gas pressures. Copyright 2005 by Princeton University.