Two-photon-ionization coefficients of propane, 1-butene, and methylamines

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Abstract
Ion currents produced by two-photon ionization were investigated for several organic molecules. At low charge density, the ion current is proportional to the product of gas pressure and the square of laser intensity. At high gas pressure and high laser intensity, the ion current saturates. The saturation effect is well interpreted by a model including electron attachment and charge recombination processes. The two-photon-ionization coefficients were determined from the low ion current data. Among the molecules studied, trimethylamine has the highest coefficient of 3.6×10−26 cm4/W at the KrF laser wavelength of 248 nm. Such a high photoionization coefficient indicates that trimethylamine could be used to produce a high density of initial electrons for laser-controlled switches. The present results could also be used to develop new techniques for investigating the electron attachment and charge recombination processes at high gas pressures.

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