Sequential two-photon photoexcitation of SO2 at 248 nm is found to lead to a number of primary fragments including S(3P) and SO(X 3Σ−). Further excitation of some of these photoproducts was also observed, occurring by both linear and two-quantum mechanisms. The resulting molecular X←B (v\,2) ultraviolet fluorescence from SO and the atomic 3P←3S vacuum ultraviolet emission from S atoms were detected and an analysis of the energy flow patterns was made.
Photolytic studies performed at 193 nm demonstrate that NO in the highly excited D(v = 1,5) and E(v = 0) states is generated from N2O during irradiation in three sequential steps involving photodissociation, chemical reaction, and photoexcitation. The resulting NO fluorescence (160–230 nm) was analyzed with a system of rate equations, and the temporal behavior, intensity dependence, and pressure dependence were found to be consistent with a simple kinetic model. The quenching coefficient of NO by N2, Ar, and N2O were determined in this analysis to be qN2 = (2.7±0.8)×10−11 cm3 sec−1, qAr = (6.6±1.4)×10−11 cm3 sec−1, and qN2O = (1.5±0.4)×10−10 cm3 sec−1. Finally, dramatic changes in the spectral distribution of the ultraviolet NO fluorescence due to collisions with He were observed, which contrasts with the absence of spectral redistribution in collisions involving N2, Ar, and N2O.
A 40-mJ ArF* laser with pulse duration ∼10 ps and spatial and spectral properties close to the transform limits is described. Substantial extraction of the available energy from the final amplifier is demonstrated, a fact providing direct evidence against the presence of significant nonlinear losses in the amplifying medium up to an intensity of ∼1 GW/cm.2
An extremely high spectral brightness KrF* (248 nm) excimer source is described. This instrument combines the property of continuous tunability over the full gain profile with the following output pulse characteristics: pulse energy ∼60 mJ, pulse duration ∼10 nsec, spectral width 15030 MHz, absolute frequency control to within 300 MHz, and beam divergence ∼50 μrad. Within the uncertainty of measurement, the spectral width of the output radiation is Fourier transform limited, and the beam divergence corresponds to the diffraction of the radiating aperture.
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