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We have measured (e,2e) triple differential cross sections (TDCS) for the electron-impact ionisation of phenol with coplanar asymmetrical kinematics for an incident electron energy of 250 eV. Experimental measurements of the angular distribution of the slow outgoing electrons at 20 eV are obtained when the incident electron scatters through angles of - 5°, -10°, and -15°, respectively. The TDCS data are compared with calculations performed within the molecular 3-body distorted wave model. In this case, a mixed level of agreement, that was dependent on the kinematical condition being probed, was observed between the theoretical and experimental results in the binary peak region. The experimental intensity of the recoil features under all kinematical conditions was relatively small, but was still largely underestimated by the theoretical calculations. [ABSTRACT FROM AUTHOR]

Cross section data for electron scattering from DNA are important for modelling radiation damage in biological systems. Triply differential cross sections for the electron impact ionization of the highest occupied outer valence orbital of tetrahydrofurfuryl alcohol, which can be considered as an analogue to the deoxyribose backbone molecule in DNA, have been measured using the (e,2e) technique. The measurements have been performed with coplanar asymmetric kinematics at an incident electron energy of 250 eV, an ejected electron energy of 20 eV, and at scattered electron angles of -5°, -10°, and -15°. Experimental results are compared with corresponding theoretical calculations performed using the molecular 3-body distorted wave model. Some important differences are observed between the experiment and calculations. [ABSTRACT FROM AUTHOR]

Charge transport of unintentionally doped GaSb nanowires was studied through the fabrication and analysis of nanowire field effect transistors (FETs). In this work, both temperature dependent and voltage dependent measurements demonstrate various operating regimes, including a transition from linear current-voltage behavior at low bias to a space-charge limited current (SCLC) at large bias. Analysis of the voltage and temperature variation in the SCLC regime provided quantitative information about the trap energy distribution in the nanowires, which, after thermal annealing, has been shown to reduce from 0.26 eV to 0.12 eV. The measurements also indicate that the GaSb nanowire FETs exhibit n-type behavior, which is likely due to oxygen impurities in the nanowires. [ABSTRACT FROM AUTHOR]

The ionization energy spectra and electron momentum distributions of formamide were investigated using the high-resolution electron momentum spectrometer in combination with high level calculations. The observed ionization energy spectra and electron momentum distributions were interpreted using symmetry adapted cluster-configuration interaction theory, outer valence Green function, and DFT-B3LYP methods. The ordering of 10a′ and 2a″ orbitals of formamide was assigned unambiguously by comparing the experimental electron momentum distributions with the corresponding theoretical results, i.e., 10a′ has a lower binding energy. In addition, it was found that the low-frequency wagging vibration of the amino group at room temperature has noticeable effects on the electron momentum distributions. The equilibrium-nuclear-positions-approximation, which was widely used in electron momentum spectroscopy, is not accurate for formamide molecule. The calculations based on the thermal average can evidently improve the agreement with the experimental momentum distributions. [ABSTRACT FROM AUTHOR]

Cross-section data for electron impact induced ionization of bio-molecules are important for modelling the deposition of energy within a biological medium and for gaining knowledge of electron driven processes at the molecular level. Triply differential cross sections have been measured for the electron impact ionization of the outer valence 7b2 and 10a1 orbitals of pyrimidine, using the (e, 2e) technique. The measurements have been performed with coplanar asymmetric kinematics, at an incident electron energy of 250 eV and ejected electron energy of 20 eV, for scattered electron angles of -5°, -10°, and -15°. The ejected electron angular range encompasses both the binary and recoil peaks in the triple differential cross section. Corresponding theoretical calculations have been performed using the molecular 3-body distorted wave model and are in reasonably good agreement with the present experiment. [ABSTRACT FROM AUTHOR]

Electron momentum spectroscopy and symmetry adapted cluster-configuration interaction (SAC-CI) theory were combined to study electron correlation effects in nitrous oxide molecule (N2O). The SAC-CI General-R method accurately reproduced the experimental ionization spectrum. This bench-marked method was also introduced for calculating the momentum distributions of N2O Dyson orbitals. Several calculated momentum distributions with different theoretical methods were compared with the high resolution experimental results. In the outer-valence region, Hartree-Fock (HF), density functional theory (DFT), and SAC-CI theory can well describe the experimental momentum distributions. SAC-CI presented a best performance among them. In the inner-valence region, HF and DFT cannot work well due to the severe breaking of the molecular orbital picture, while SAC-CI still produced an excellent description of experimental momentum profiles because it can accurately take into account electron correlations. Moreover, the thermally averaged calculation showed that the geometrical changes induced by the vibration at room temperature have no noticeable effects on momentum distribution of valence orbitals of N2O. [ABSTRACT FROM AUTHOR]

Triple differential cross sections for the electron-impact ionization of the outer valence orbital of tetrahydrofuran have been measured using the (e, 2e) technique. The measurements have been performed with coplanar asymmetric kinematics, at an incident electron energy of 250 eV and at an ejected electron energy of 10 eV, over a range of momentum transfers. The experimental results are compared with theoretical calculations carried out using the molecular three-body distorted wave model. The results obtained are important for gaining an understanding of electron driven processes at a molecular level and for modeling energy deposition in living tissue. [ABSTRACT FROM AUTHOR]

We study the distribution of the emitted power between the free-space modes and guided modes in a semiconductor nanowire. We analyze all possible dipole orientations and nanowire radii in the range from very small to comparable to the wavelength. Our theoretical approach is based on the Fourier transform technique and equivalent to the construction of Green’s function for a dipole at an arbitrary location inside the nanowire. We show that the total emitted power can exhibit rather pronounced oscillations as a function of the frequency and radius. The far-field pattern is also very sensitive to the frequency and radius, especially in the regime when leaky (or whispering gallery) modes with finite axial wave numbers are excited. We discuss the enhancement of emission into guided modes due to formation of Fabry-Pérot cavity in a finite length nanowire. Our results yield directly the extraction efficiencies and angular distribution of radiation of light-emitting diodes made of nanowires. [ABSTRACT FROM AUTHOR]

The binding energy spectra and momentum distributions of all valence orbitals of propene were studied by electron momentum spectroscopy (EMS) as well as Hartree–Fock and density functional theoretical calculations. The experiment was carried out at impact energies of 1200 eV and 600 eV on the state-of-the-art EMS spectrometer developed at Tsinghua University recently. The experimental momentum profiles of the valence orbitals were obtained and compared with the various theoretical calculations. Moreover, the experiment with a new analysis method presents a strong support for the correct ordering of the orbital 8a′ and 1a″, i.e., 9a′<8a′<1a″<7a′. [ABSTRACT FROM AUTHOR]

The electron binding energy spectra and momentum profiles of the valence orbitals of difluoromethane, also known as HFC32 (HFC—hydrofluorocarbon) (CH2F2), have been studied by using a high resolution (e,2e) electron momentum spectrometer, at an impact energy of 1200 eV plus the binding energy, and by using symmetric noncoplanar kinematics. The experimental momentum profiles of the outer valence orbitals and 4a1 inner valence orbital are compared with the theoretical momentum distributions calculated using Hartree–Fock and density functional theory (DFT) methods with various basis sets. In general, the shapes of the experimental momentum distributions are well described by both the Hartree–Fock and DFT calculations when large and diffuse basis sets are used. However, the result also shows that it is hard to choose the different calculations for some orbitals, including the methods and the size of the basis sets employed. The pole strength of the ionization peak from the 4a1 inner valence orbital is estimated. © 2005 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The binding energy spectra and electron distributions in momentum space of the valence orbitals of cyclopentane (C5H10) are studied by Electron Momentum Spectroscopy (EMS) in a noncoplanar symmetric geometry. The impact energy was 1200 eV plus binding energy and energy resolution of the EMS spectrometer was 1.2 eV. The experimental momentum profiles of the outer valence orbitals are compared with the theoretical momentum distributions calculated using Hartree–Fock and density functional theory (DFT) methods. The shapes of the experimental momentum distributions are generally quite well described by both the Hartree–Fock and DFT calculations when the large and diffuse basis sets are used. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Electron density distributions in momentum space of the valence orbitals of ethane (C[sub 2]H[sub 6]) are measured by electron momentum spectroscopy (EMS) in a noncoplanar symmetric geometry. The impact energy was 1200 eV plus binding energy and energy resolution of the EMS spectrometer was 0.95 eV. The measured experimental momentum distributions of the valence orbitals are compared with Hartree-Fock and density functional theory (DFT) calculations. The shapes of the experimental momentum distributions are generally quite well described by both the Hartree-Fock and DFT calculations when large and diffuse basis sets are used. A strong "turn up" of the experimental cross section is observed for the HOMO 1 e[sub g] orbital in the low momentum region, compared with the theoretical calculations. The pole strengths for the main ionization peaks in the inner-valence region are estimated. [ABSTRACT FROM AUTHOR]

Investigates the electron-hole plasma heating and ultrafast modulation in a semiconductor laser under a terahertz electrical field using a set of hydrodynamic equations derived from the semiconductor Bloch equations. Self-consistent treatment of lasing and heating processes; Limitation to bandwidth achievable with scheme in ultrafast modulation.

Parasitic wasps rely on olfaction to locate their hosts in complex chemical environments. Odorant receptors (ORs) function together with well‐conserved odorant coreceptors (ORcos) to determine the sensitivity and specificity of olfactory reception. Campoletis chlorideae (Hymenoptera: Ichneunmonidae) is a solitary larval endoparasitoid of the cotton bollworm, Helicoverpa armigera, and some other noctuid species. To understand the molecular basis of C. chlorideae's olfactory reception, we sequenced the transcriptome of adult male and female heads (including antennae) and identified 211 OR transcripts, with 95 being putatively full length. The tissue expression profiles, as assessed by reverse‐transcription PCR, showed that seven ORs were expressed only or more highly in female antennae. Their functions were analysed using the Xenopu slaevis oocyte expression system and two‐electrode voltage‐clamp recordings. CchlOR62 was tuned to cis‐jasmone, which was attractive to female C. chlorideae adults and H. armigera larvae in the subsequent behavioural assays. Further bioassays using caged plants showed that the parasitism rate of H. armigera larvae by C. chlorideae on cis‐jasmone‐treated tobacco plants was higher than on the control plants. Thus, cis‐jasmone appears to be an important infochemical involved in the interactions of plants, H. armigera and C. chlorideae, and CchlOR62 mediates the attractiveness of cis‐jasmone to C. chlorideae. [ABSTRACT FROM AUTHOR]