Desk-top size high repetition rate 46.9 NM capillary discharge laser as photoionization source for photochemistry applications
Date
2006
Authors
Heinbuch, Scott, author
Rocca, Jorge J., advisor
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Abstract
A portable high repetition rate desktop-size capillary discharge laser emitting at a wavelength of 46.9 nm (26.5 eV photon energy) was demonstrated and used as a photoionization source in nanocluster mass spectroscopy. The high photon energy allows the single-photon ionization of nanoclusters and other molecules, which, due to their high ionization potential, would otherwise require undesirable multi-photon ionization. This Ne-like Ar capillary discharge laser occupies a table area of approximately 0.4 x 0.4 m², smaller than that occupied by many widely used ultraviolet gas lasers. The laser's power supplies and gas handling system are designed to fit into small racks that can be placed underneath a standard optical table. The main spark-gap is electrically triggered to allow synchronization of the laser pulses with those of other lasers in photochemistry applications. Experiments were performed to characterize the laser output energy, average power and timing jitter. Tests were conducted to determine the capillary lifetime. Laser pulses with energy ~ 13 μJ were generated at 12 Hz repetition rate by single pass amplification in a 21 cm long Ne-like Ar capillary discharge plasma column. The standard deviation of the jitter was found to be 5 ns. Capillary lifetime tests at 12 Hz repetition rate determined that the laser output energy decays by a factor of two after about 2 10⁴ - 3 10⁴ shots. The laser was installed in a photochemistry laboratory where it is operated for many hours on a daily basis. The laser was successfully used as a single photon photoionization source for the study of hydrogen bonded nanoclusters and other small molecules using time of flight mass spectroscopy. The first mass spectra of water nanoclusters and other small molecules using this source have been obtained.
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Subject
X-ray lasers
Photoionization