627 research outputs found
Prediction of the derivative discontinuity in density functional theory from an electrostatic description of the exchange and correlation potential
We propose a new approach to approximate the exchange and correlation (XC)
functional in density functional theory. The XC potential is considered as an
electrostatic potential, generated by a fictitious XC density, which is in turn
a functional of the electronic density. We apply the approach to develop a
correction scheme that fixes the asymptotic behavior of any approximated XC
potential for finite systems. Additionally, the correction procedure gives the
value of the derivative discontinuity; therefore it can directly predict the
fundamental gap as a ground-state property.Comment: 5 pages, 4 figure
Threshold photoelectron photoion coincidence spectroscopy of trichloroethene and tetrachloroethene
The threshold photoelectron, the threshold photoelectron photoion coincidence and ion breakdown spectra of trichloroethene and tetrachloroethene have been recorded from 9 – 22 eV. Comparisons with the equivalent data for the three dichloroethene molecules and theoretical calculations highlight the nature of the orbitals involved during photoionisation in this energy range. The ground electronic state of CHCl (CCl) is bound, with excited valence states dissociating to CHCl (CCl) and CHCl (CCl). Appearance energies suggest that CHCl forms from CHCl by loss of two chlorine atoms, whereas CCl forms from CCl by loss of a Cl molecule. The translational kinetic energy release into CHCl (CCl) + Cl is determined as a function of energy. In both cases, the fraction of the available energy released into translational energy of the two products decreases as the photon energy increases
Absolute Electron Scattering Cross Sections for the CF2 Radical
Using a crossed electron-molecular beam experiment, featuring a skimmed nozzle beam with pyrolytic radical production, absolute elastic cross sections for electron scattering from the CF2 molecule have been measured. A new technique for placing measured cross sections on an absolute scale is used for molecular beams produced as skimmed supersonic jets. Absolute differential cross sections for CF2 are reported for incident electron energies of 30–50 eV and over an angular range of 20–135 deg. Integral cross sections are subsequently derived from those data. The present data are compared to new theoretical predictions for the differential and integral scattering cross sections, as calculated with the Schwinger multichannel variational method using the static-exchange and static-exchange plus polarization approximations
Laser induced electron diffraction: a tool for molecular orbital imaging
We explore the laser-induced ionization dynamics of N2 and CO2 molecules
subjected to a few-cycle, linearly polarized, 800\,nm laser pulse using
effective two-dimensional single active electron time-dependent quantum
simulations. We show that the electron recollision process taking place after
an initial tunnel ionization stage results in quantum interference patterns in
the energy resolved photo-electron signals. If the molecule is initially
aligned perpendicular to the field polarization, the position and relative
heights of the associated fringes can be related to the molecular geometrical
and orbital structure, using a simple inversion algorithm which takes into
account the symmetry of the initial molecular orbital from which the ionized
electron is produced. We show that it is possible to extract inter-atomic
distances in the molecule from an averaged photon-electron signal with an
accuracy of a few percents
The photoionization dynamics of the three structural isomers of dichloroethene
Using tunable vacuum-UV radiation from a synchrotron, the threshold photoelectron spectrum, threshold photoelectron photoion coincidence spectrum and ion breakdown diagram of the 1,1, cis-1,2 and trans-1,2 isomers of CHCl have been recorded in the range 9-23 eV. The energies of the peaks in the threshold photoelectron spectrum are in good agreement with outer-valence Greens function caculations. The major difference between the isomers, both predicted and observed experimentally is that the Fï€ and Gï€ states of CHCl are approximately degenerate for 1,1 and trans-1,2, but well separated for the cis-1,2 isomer. The ground and low-lying valence states of CHCl are bound, with higher-lying states dissociating to CHCl or CH. The translational kinetic energy release into CHCl + Cl is determined as a function of energy. Isolated-state behaviour for the low-lying electronic states of CHCl becomes more statistical as the energy increases
Time-resolved multi-mass ion imaging: femtosecond UV-VUV pump-probe spectroscopy with the PImMS camera
The Pixel-Imaging Mass Spectrometry (PImMS) camera allows for 3D charged
particle imaging measurements, in which the particle time-of-flight is recorded
along with position. Coupling the PImMS camera to an ultrafast
pump-probe velocity-map imaging spectroscopy apparatus therefore provides a
route to time-resolved multi-mass ion imaging, with both high count rates and
large dynamic range, thus allowing for rapid measurements of complex
photofragmentation dynamics. Furthermore, the use of vacuum ultraviolet
wavelengths for the probe pulse allows for an enhanced observation window for
the study of excited state molecular dynamics in small polyatomic molecules
having relatively high ionization potentials. Herein, preliminary time-resolved
multi-mass imaging results from CFI photolysis are presented. The
experiments utilized femtosecond UV and VUV (160.8~nm and 267~nm) pump and
probe laser pulses in order to demonstrate and explore this new time-resolved
experimental ion imaging configuration. The data indicates the depth and power
of this measurement modality, with a range of photofragments readily observed,
and many indications of complex underlying wavepacket dynamics on the excited
state(s) prepared
First-principles modelling of molecular single-electron transistors
We present a first-principles method for calculating the charging energy of a
molecular single-electron transistor operating in the Coulomb blockade regime.
The properties of the molecule are modeled using density-functional theory, the
environment is described by a continuum model, and the interaction between the
molecule and the environment are included through the Poisson equation. The
model is used to calculate the charge stability diagrams of a benzene and
C molecular single-electron transistor
LAYANAN ADMINISTRASI DALAM PELAKSANAAN KURIKULUM DI MADRASAH TSANAWIYAH NURUL HUDA MUARO JAMBI
Penelitian ini membahas tentang layanan administrasi yang ada di Madrasah
Tsanawiyah Nurul Huda Muaro Jambi. Penelitian ini merupakan penelitian kualitatif
deskriptif dengan menggunakan teknik pengumpulan data observasi, wawancara, dan
dokumentasi, sedangkan teknik analisis data yang digunakan adalah reduksi data,
penyajian data dan penarikan kesimpulan. Teknik keabsahan data yaitu memakai
triangulasi sumber, triangulasi teknik dan triangulasi waktu. Layanan administrasi
adalah layanan yang harus diterapkan oleh pihak sekolah dalam mendukung kegiatan
kurikulum yang ada di Madrasah. Hasil penelitian menunjukkan bahwa terdapat
Kendala yang menyebabkan layanan administrasi di madrasah tidak berjalan dengan
efektif dan efisien, baik layanan internal maupun layanan eksternal. Faktor yang
mempengaruhi kinerja staff administrasi ialah kurangnya personil dan kurangnya
sarana dan prasarana yang menunjang kerja staff. Upaya yang dilakukan kepala
sekolah dan kepala tata usaha dalam meningkatkan layanan administrasi yaitu
mengadakan musyawarah terhadap seluruh anggota yang terlibat dalam sekolah untuk
mendapatkan solusi yang layak dalam kinerjanya
SAR Performance of Rectangular Microstrip Antenna for Breast Cancer Hyperthermia Treatment with Different Period of Treatment Procedure
Cancer treatment using hyperthermia techniques recently become the interest among
researchers in investigating and improving certain deficiencies of the treatment since this
treatment has the potential to denaturate cancer into necrotic tissue. Hyperthermia uses high heat
from 41℃ to 45℃ at a certain period of time. It is difficult to control the focus position distance
of heat distribution on the treated tissue. Therefore, this paper presents the rectangular microstrip
as hyperthermia applicator, which deliver the heat on the targeted treated breast cancer tissue
with different period of time in order to obtain sufficient heat or SAR distribution. Sim4LifeLight
software simulator is used to design, simulate and generate the specific absorption rate (SAR)
distribution on the treated tissue. Three frequencies of 434MHz, 915MHz and 2450MHz are
used to be compared. Based on the results, 2450MHz shows better performance than the other
two frequencies. However, there is a certain limitation, such as skin burn and unwanted hotspots,
that need to be further improved. The cancer is sufficiently heating at different operating
frequencies at different periods of procedures
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