The relaxation dynamics of the photoexcited hydrated electron have been subject to conflicting interpretations. Here, we report time-resolved photoelectron spectra of hydrated electrons in a liquid microjet with the aim of clarifying ambiguities from previous experiments. A sequence of three ultrashort laser pulses (~100 femtosecond duration) successively created hydrated electrons by charge-transfer-to-solvent excitation of dissolved anions, electronically excited these electrons via the s→p transition, and then ejected them into vacuum. Two distinct transient signals were observed. One was assigned to the initially excited p-state with a lifetime of ~75 femtoseconds, and the other, with a lifetime of ~400 femtoseconds, was attributed to s-state electrons just after internal conversion in a nonequilibrated solvent environment. These assignments support the nonadiabatic relaxation model.
Fluorocarbon film deposition onto Si and its influence on the measured Si etch rate in CF4/H2 reactive ion etching in a symmetric two electrode reactor has been studied as a function of CF4/H2 feed gas composition, total gas flow, and applied rf power. For reactive ion etching, the fluorocarbon film thickness on Si increases as the percentage x of H2 in CF4/x% H2 is increased. The fluorocarbon film thickness depends on the total gas flow and is greater for greater gas flows. The observed Si etch rate is controlled by the fluorocarbon film. The Si etch rate is directly proportional to the inverse of the F,C-film thickness for fluorocarbon films thicker than ∼10 Å, which may indicate a diffusion-limited mechanism. Both in-diffusion of fluorine and out-diffusion of SiF4 etch product through the fluorocarbon film are consistent with the decrease of the Si etch rate. The relative importance of the lowering of the atomic F concentration in the gas phase on the Si etch rate, e.g., by the H scavenging mechanism, has also been studied. This reaction can be important for conditions where either the inner walls of the etching apparatus can be maintained free of C,F film throughout the etching experiment, and/or a low hydrogen concentration (≤20%) in the CF4/H2 feed gas is used. For a fixed gas composition of CF4/40% H2, the rf-power dependence of the C,F-film thickness and of the Si etch rate was studied. In reactive ion etching, i.e., if rf power is supplied to the bottom (substrate) electrode, at first a monotonic rise in deposited fluorocarbon film thickness with increasing rf power is observed; at high rf-power levels a dramatic decrease in the C,F-layer thickness occurs, which is concomitant with a greater intensity of near surface lattice disorder (from ion channeling studies) and Si etching. Silicon etching is not observed for lower rf powers. In cases where rf power was supplied to the top electrode only, C,F-film deposition has been observed and no Si etching. These data are consistent with a recombinant model of etch anisotropy.
Limber pine (Pinus flexilis) is a keystone species of high-elevation forest ecosystems of western North America, but some parts of the geographic range have high infection and mortality from the non-native white pine blister rust caused by Cronartium ribicola. Genetic maps can provide essential knowledge for understanding genetic disease resistance as well as local adaptation to changing climates. Exome-seq was performed to construct high-density genetic maps in two seed families. Composite maps positioned 9612 unigenes across 12 linkage groups (LGs). Syntenic analysis of genome structure revealed that the majority of orthologs were positional orthologous genes (POGs) with localization on homologous LGs among conifer species. Gene ontology (GO) enrichment analysis showed relatively fewer constraints for POGs with putative roles in adaptation to environments and relatively more conservation for POGs with roles in basic cell function and maintenance. The mapped genes included 639 nucleotide-binding site leucine-rich repeat genes (NBS-LRRs), 290 receptor-like protein kinase genes (RLKs), and 1014 genes with potential roles in the defense response and induced systemic resistance to attack by pathogens. Orthologous loci for resistance to rust pathogens were identified and were co-positioned with multiple members of the R gene family, revealing the evolutionary pressure acting upon them. This high-density genetic map provides a genomic resource and practical tool for breeding and genetic conservation programs, with applications in genomewide association studies (GWASs), the characterization of functional genes underlying complex traits, and the sequencing and assembly of the full-length genomes of limber pine and related Pinus species.
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