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The dependence of excited-state lifetime, fluorescence quantum yield and isomerization rate of organic dye molecules on solvent viscosity has been a subject of numerous experimental and theoretical investigations. To explain the viscosity dependence of excited-state lifetime in this paper the temporal behavior of the excited state population is calculated for several models of the molecular relaxation process by a computer simulation incorporating both the stochastical motion of large molecular parts in the excited state and relaxation transitions. The described method is applicable to calculating the probability of changing the electronic state as a function of time and internal rotation coordinate.

In the paper we report about the progress made at XTREME technologies in the development of EUV sources based on gas discharge produced plasma (GDPP) technologies and laser produced plasma (LPP) technologies.First prototype xenon GDPP sources of the type XTS 13-35 based on the Z-pinch principle with 35 W power in 2π sr have been integrated into micro-exposure tools from Exitech, UK. Specifications of the EUV sources and experience of integration as well as data about component and optics lifetime are presented.In the source development program for Beta exposure tools and high volume manufacturing exposure tools both tin and xenon have been investigated as fuel for the EUV sources. Development progress in porous metal cooling technology as well as pulsed power circuit design has led to GDPP sources with xenon fuel continuous operating with an output power of 200 W in 2π sr at 4500 Hz repetition rate. With tin fuel an output power of 400 W in 2π sr was obtained leaving all other conditions unaltered with respect to the xenon based source. The performance of the xenon fueled sources is sufficiently good to fulfill all requirements up to the beta tool level.For both the xenon and the tin GDPP sources detailed data about source performance are reported, including component lifetime and optics lifetime. The status of the integration of the sources with grazing incidence collector optics is discussed. Theoretical estimations of collection efficiencies are compared with experimental data to determine the loss mechanisms in the beam path. Specifically contamination issues related to tin as target material as well as debris mitigation in tin sources is addressed.As driver lasers for the LPP source research diode-pumped Nd:YAG lasers have been used to generate EUV emitting plasma. As target material xenon has been employed. Conversion efficiencies have been measured and currently the maximum conversion efficiency amounts to 1 %. The laser driver power of 1.2 kW is currently achieved with a masteroscillator power-amplifier industrial Nd:YAG laser configuration. With this laser, xenon based EUV sources have achieved 10 W EUV power at 13.5 nm emitted into 2π sr solid angle.For the xenon LPP sources detailed data about the achieved source performance including component lifetime and optics lifetime are reported. The status of the integration of the sources with normal incidence collector optics is shown.The potentials and limits of Z-pinch GDPP and LPP EUV source technologies to achieve high volume manufacturing specifications are discussed in this paper.