Search

ABSTRACTWe assessed the growth and adaptability of triploid acacia clones in comparison with commercially planted diploid clones of the same taxa to age three years at three contrasting sites in north, central and south Viet Nam. Application of phosphorus fertiliser at planting gave a growth response only in the trial in central Viet Nam. One triploid Acaciahybrid (Acacia auriculiformis× mangium) clone was constantly the best performer in all sites, achieving mean annual increments at three years of 30.1, 26.6 and 32.1 m3ha−1in northern, central and southern Viet Nam, respectively. Two other triploid hybrid clones outperformed the diploid controls in southern Viet Nam. A single triploid A. auriculiformisclone and two diploid clones of this species grew much more slowly. Triploid Acaciahybrid clones had a lower incidence of Corticium salmonicolor(pink disease) and Ceratocystisdisease symptoms than did diploid hybrid clones. The wind-firmness of triploid Acaciahybrid clones was comparable with or better than the diploid hybrid clones. Triploid breeding offers a promising new pathway in the development of improved Acaciaplanting material.

It is well known in the industry that the technology nodes from 30nm and below will require model based SRAF / OPC for critical layers to meet production required process windows. Since the seminal paper by Saleh and Sayegh[1][2] thirty years ago, the idea of using inverse methods to solve mask layout problems has been receiving increasing attention as design sizes have been steadily shrinking. ILT in its present form represents an attempt to construct the inverse solution to a constrained problem where the constraints are all possible phenomena which can be simulated, including: DOF, sidelobes, MRC, MEEF, EL, shot-count, and other effects. Given current manufacturing constraints and process window requirements, inverse solutions must use all possible degrees of freedom to synthesize a mask. Various forms of inverse solutions differ greatly with respect to lithographic performance and mask complexity. Factors responsible for their differences include composition of the cost function that is minimized, constraints applied during optimization to ensure MRC compliance and limit complexity, and the data structure used to represent mask patterns. In this paper we describe the level set method to represent mask patterns, which allows the necessary degrees of freedom for required lithographic performance, and show how to derive Manhattan mask patterns from it, which can be manufactured with controllable complexity and limited shot-counts. We will demonstrate how full chip ILT masks can control e-beam write-time to the level comparable to traditional OPC masks, providing a solution with maximized lithographic performance and manageable cost of ownership that is vital to sub-30nm node IC manufacturing.

Femtosecond multicolor pump−probe spectroscopy on the prototypical intramolecular electron-transfer compound ([(NH3)5RuNCRu(CN)5]^-; RuRu) in aqueous solution is reported for the first time with sufficient time resolution and spectral coverage to monitor the complete spectral dynamics. From the dynamic absorption spectrum, constructed from the pump−probe data obtained over a wide range of probe wavelengths (570−1300 nm), accurate measurement of the electron transfer (ET) time (1/kET) have been obtained by a global analysis of the data. The data have lead to new insights on the role of solvent and solute nuclear motions in the ET process. Additionally, pump−probe experiments with variable wavelength pump pulses have revealed the presence of a pump wavelength-dependent dynamic feature at early time, which has been assigned to stimulated emission from nonequilibrium excited states.

We investigate the time scale for hydrated electron solvation as a function of the initial configuration of the electron/water system. The experiments employ various 2-pulse and 3-pulse femtosecond pulse sequences that allow for controllable preparation of the various optically excited and precursor states of the equilibrated hydrated electron. We observe that the conduction band electron, which is produced by detrapping of the hydrated electron, has the slowest time scale for electron solvation with an average solvation time constant of 400 fs. In contrast, the solvation dynamics are significantly faster for electrons that are produced in “pre-solvated” environments. These latter examples include the excited p-state of the hydrated electron and the precursor states involved in UV femtosecond multiphoton ionization of water.

Experimental information on the spatial extent of the putative p and conduction band states of the hydrated electron (eeq) has been obtained by monitoring and controlling the electron/hole spatial separation of a photogenerated eeq/hole pair using a femtosecond laser pulse sequence. Optical excitation of eeq with two photons is observed to dramatically alter its spatial distribution and geminate recombination yield with the hole. One-photon excitation, in contrast, has no effect on the spatial distribution. The results strongly confirm theoretical predictions on the size and location of excited states of eeq.

Femtosecond spectroscopy measurements are reported on the electron transfer, ET, reactions of the precursor states of the hydrated electron in the multiphoton ionization of water and the single-photon ionization of Fe(CN)6^4- in aqueous solutions. The ET reaction corresponds to an electron scavenging by various electron acceptors, such as Cd²⁺. Using the data reported herein, and previously published data on the scavenging kinetics of other electron precursors (e.g., from radiolysis) and optically excited states of the hydrated electron, it was shown that the rate constant of ET varies inversely with the volume of specific form of the hydrated electron. These data strongly support a unified model for the electron-transfer kinetics of many forms of delocalized electrons with localized electron acceptors in which ET rates are assumed to be proportional to the average electron density of the specific hydrated electron excited state or precursor.

A detailed investigation of ultrafast photoinduced electron transfer (ET) in a mixed valence compound ((NH3)5RuNCRu(CN)5^-; RuRu) in formamide, ethylene glycol, and glycerol was performed using variable wavelength femtosecond pump−probe spectroscopy over a broad range of pump and probe wavelengths. The ET kinetics were monitored by observing recovery of the ground state population. The spectra are highly dynamic, indicating the need for broad spectral coverage to accurately unravel the ET kinetics from excited state and ground state relaxation dynamics. ET is observed to proceed more slowly in slower solvents in a manner consistent with the Hybrid model of solution phase electron transfer. The ET time (1/e) of RuRu in ethylene glycol is 220 fs compared to 100 fs in water. As recently reported for RuRu in water, the ET time is pump wavelength independent. A previously unobserved pump wavelength dependence of the early time dynamics, however, is observed which is assigned to stimulated emission prior to vibrational relaxation in the excited state. The early time dynamics of the stimulated emission is solvent dependent as demonstrated by the pump wavelength dependence while probing at the red edge of the static absorption spectra. The oscillatory features observed in the pump−probe signal are assigned to vibrational coherence on the ground electronic state created primarily by resonant impulsive stimulated Raman scattering (RISRS). The dephasing time of the vibrational coherence is solvent dependent as are the vibrational population relaxation rates. The wavelength dependent phase and amplitude of the oscillations show differences from typical RISRS signals, which suggest non-Condon contributions to the oscillations. The solvent dependence of the oscillation amplitude suggests the presence of vibrationally impulsive internal conversion for the fastest reaction, RuRu in water. Extremely slow solvent dynamics are observed in the slow solvents despite a very short excited-state lifetime which indicates a solvent response outside the regime of linear response.

We recently reported the first pump−probe measurements on the hydrated electron with sufficient time resolution (~35 fs) to directly observe the initial processes in the solvation dynamics of this key prototype for condensed-phase dynamics [Silva, C.; Walhout, P. K.; Yokoyama, K.; Barbara, P. F. Phys. Rev. Lett. 1998, 80, 1086]. An unprecedented relaxation process for the hydrated electron was observed that occurs on the 35−80 fs time scale and exhibits a solvent isotope effect (τ(D2O)/τ(H2O) ~ 1.4). The new process was assigned to inertial/librational motion of the water surrounding the excess electron. The present paper reports a more extensive study of the ~35 fs resolved dynamics of the hydrated electron in H2O and D2O at more probe wavelengths and as a function of pump-pulse intensity. The results are in agreement with the preliminary report and support the importance of librational water motion in the relaxation dynamics of the hydrated electron. New high excitation pulse intensity measurements reveal evidence of a high-intensity, two-photon channel involving ejection of the hydrated electron from its initial site to a different site in the solvent.