We present the characteristics of track formation on the front and rear surfaces of CR-39 produced by laser-driven protons and carbon ions. A methodological approach, based on bulk etch length, is proposed to uniquely characterize the particle tracks in CR-39, enabling comparative description of the track characteristics in different experiments. The response of CR-39 to ions is studied based on the energy dependent growth rate of the track diameter to understand the intrinsic particle stopping process within the material. A large non-uniformity in the track diameter is observed for CR-39 with thickness matching with the stopping range of particles. Simulation and experimental results show the imprint of longitudinal range straggling for energetic protons. Moreover, by exploiting the energy dependence of the track diameter, the energy resolution (δE/E) of CR-39 for few MeV protons and Carbon ion is found to be about 3%.
High-harmonic radiation emitted from molecules in a strong laser field contains information on molecular structure and dynamics. When multiple molecular orbitals participate in high-harmonic generation, resolving the contribution of each orbital is crucial for understanding molecular dynamics and for extending high-harmonic spectroscopy to more complicated molecules. We show that two-dimensional high-harmonic spectroscopy can resolve high-harmonic radiation emitted from the two highest-occupied molecular orbitals, HOMO and HOMO-1, of aligned molecules. By the application of an orthogonally polarized two-color laser field that consists of the fundamental and its second-harmonic fields to aligned CO2 molecules, the characteristics attributed to the two orbitals are found to be separately imprinted in odd and even harmonics. Two-dimensional high-harmonic spectroscopy may open a new route to investigate ultrafast molecular dynamics during chemical processes.
ArF photoresist polymers were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization and free radical polymerization (FRP). Three methacrylates with lithographic functionalities including 2-ethyl-2-adamantyl methacrylate (EAdMA), α-gamma-butyrolactone methacrylate (GBLMA), and 3-hydroxy-1-adamantyl methacrylate (HAdMA), were used as monomer components and 2-cyanoprop-2-yl-1-dithionaphthalate (CPDN) was used as the chain transfer agent (CTA). In both polymerizations, the order of monomer reactivity was GBLMA>HAdMA>>EAdMA. This caused a composition gradient in RAFT polymerization as well as composition inhomogeneity in FRP. The polymers prepared by RAFT polymerization had lower molecular weight distributions and more uniform compositions. The improvement in molecular weight distribution and composition uniformity of the polymers prepared by RAFT polymerization should be beneficial for the ArF lithography process.
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