Plasma generation in an organic molecular gas by an ultraviolet laser pulse

Plasma generation in an organic molecular gas through a one photon ionization process is studied. A one-dimensional model is derived to describe the photon flux flow and electron density evolution. Plasmas are generated in a low ionization potential gas, tetrakis (dimethylamino) ethylene (TMAE) vapor, through a one-photon ionization process by an ultraviolet laser beam (E-10 mJ, τ 17 ns) at 193 nm wavelength. The TMAE plasma characteristics are studied by means of a Langmuir probe and microwave scattering. A new method is used to measure the 193 nm ultraviolet (UV) photon absorption cross-section in TMAE. It is determined to be 1.1 ± 0.3 x 10-17 cm2 from the axial profile of electron density. The temporal evolution of the electron temperature is measured. A peak electron density of ne = 5 x 1013/cm3 and peak electron temperature of Te = 1 eV are measured at 500 mTorr TMAE pressure. The plasma decay process is studied, and the electron-ion recombination coefficient is measured to be 5.4 ± 0.5 x 10-6 cm3/s. Microwave scattering measurements are conducted to examine wave transmission, reflection, and absorption in TMAE plasma. The authors examine a high density sharp boundary plasma sheet produced by a UV sheet beam obtained from the laser output through an optical system. The microwave reflection from the plasma sheet is examined, and the potential application of a TMAE plasma as a mirror for microwave reflections is discussed. When TMAE is ionized in a higher pressure background gas (argon/helium), a highly collisional, diffuse-boundary plasma can be produced. Microwave transmission and absorption in a collisional TMAE plasma in a waveguide system is also measured. Both analytical results and experimental results will be discussed