Radical Sources |
Pyrolytic
Generation of Radicals |
Photolytic
Generation of Radicals Laser-induced
fluorescence spectroscopy of the ketenyl radical has been performed in
a colaboration with the Sandia National Laboratories, Livermore, California.
HCCO has been produced by the photolysis of ketene, CH2CO, at 193 nm in
the early portion of a free jet expansion. The photolysis yield at 193
nm for H+HCCO is ~37% [1].
Degenerate four-wave mixing of OH in the molecular beam has been observed
in our labs. OH radicals are produced by photolysis of t-butyl-hydroperoxide,
(CH3)3COOH, at 248 nm. [1] L.R. Brock, B. Mischler, and E.A. Rohlfing, "Laser-induced fluorescence spectroscopy of the B-tilde [sup 2] Pi--X-tilde [sup 2]A[sup [double-prime]] band system of HCCO and DCCO", The Journal of Chemical Physics, vol. 110, Apr. 1999, pp. 6773-6781. |
Pin-hole Discharge Source | ||
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The discharge assembly containing a set of electrically isolated stainless steel disc electrodes mounted on the valve body (general valve, PARKER) by glass ceramic spaces (MACOR). A typical experimental procedure starts with a trigger to the solenoid valve to expand a precursor diluted in a rare gas (for example C2H2 in Ar). At a variable time after the initial trigger for the valve, a high-voltage pulse of ≈ 800 V and adjustable duration is applied to the discharge electrodes. By changing the polaritiy of the discharge, the direction of the electrons to either co- or counter-propagation with respect to the molecular beam can be chosen. A careful optimization of the voltage, trigger delay, trigger duration an polarity yields an intense and remarkably stable molecular beam. |
Slit Discharge Source Discharge assembly containing a set of electrically isolated steel electrodes mounted on a multi-channel body by glass ceramic spacers. The planar, two-dimensional expansion through a long and narrow slit offers an essentially Doppler-free environment. The higher density of the radicals promotes equilibration of the translational and internal degrees of freedom. In addition, the two-dimensional geometry is optimally suited for a boxcars configuration of the four-wave mixing experiments. |