REMPI process shown in an energy level diagram. The molecule absorbs two photons to reach a resonant state, from which it absorbs one more to ionize. From the ionized state the molecule then emits a photon to reach a final ionized state, before it will decay back down to the ground state. This REMPI process is seen in with 193 nm laser radiation, where the ionized emits at 391 nm to decay from the ionized state (Ref. 5).
Energy level diagram of two molecules where species one absorbs 2 photons and transfers that energy to species two via collisional excitation energy transfer. The second molecule then subsequently absorbs an additional photon to become ionized and decays down to a final ionized state as seen in the REMPI process discussed earlier.
Experimental setup of 193 nm ArF laser experiment focused in a pressure and gas species controlled chamber. Experimental diagnostics include a fast ICCD camera as well as a spectrometer for optical spectroscopy measurements. Timing and triggering of all devices is controlled by a remote computer utilizing LABVIEW software.
Intensity required for CC breakdown in air compared with the intensity of both an 18 and 1.3 cm focal length lens. Note that at 1 atm the 1.3 cm lens is above the threshold required for breakdown and the 18 cm is more than two orders of magnitude below.
Plasma formation at . A gate time of 1.2 ns is used. It is interesting to note the inhomogeneous nature of the plasma at very early times.
Plasma formation at right before the laser pulse has ended. A gate time of 1.2 ns is used. The waist of the beam is in diameter.
Plasma formation at . A gate time of 1.2 ns is used.
Plasma formation at . A gate time of 100 ns is used as the plasma is emitting less light.
Plasma formation at . A gate time of 100 ns is used.
Log-log plot of breakdown intensity vs varying laser intensity in a mix of 90% and 10% at 50 Torr. The plot yields a degree of nonlinearity of 2.11 with a correlation coefficient of 99%.
Optical breakdown intensity of the first negative band head at 391.4 nm as a function of concentration in a mix for three different pressures: 50, 100, and 200 Torr.
Breakdown intensity of the 391.4 nm emission from the first negative system as a function of pressure for different concentrations of in .
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