Adsorption of PTCDA and C60 on KBr(001): electrostatic interaction versus electronic hybridization

A plot of differential charge density shows opposite electron density variation in two slabs near PTCDA and KBr(001), revealing electrostatic attraction as the primary interaction between aromatic molecules and insulator substrates.

Preparation and Electronic Property Investigation of Zinc(II)-Schiff Base Complexes in the Confined Space

Metal-Schiff base complexes have attracted continued research interest regarding their intriguing and useful features, while the electronic properties of these complexes in the confined space have not been sufficiently addressed in previous studies. In this work, a new zinc(II)-Schiff base complex bis(N-dodecyl salicylideneiminato)Zn(II) (1) was synthesized and subsequently loaded in an inorganic solid host. A large red shift (~40 nm) of the absorption onset was recorded, when the microenvironment of1changed from the solvent ethanol to the inorganic solid medium, evidencing the confined space effect. The marked shift of the absorption onset was associated with a band-gap reduction between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). Theoretical calculation results showed that the confined space effect is distance dependent and exerts a more profound influence on the HOMO than the LUMO within an effective distance range. An initial study implied that the confined space effect is also accompanied with the electron density variation.

Nonlinear dynamics of the filamentation of the resistive instability of a current-carrying plasma

The filamentation of the resistive instability in a weakly ionized quasi-neutral current-carrying plasma in the diffusion frequency region in the nonlinear regime is investigated. By using the magnetohydrodynamics equations and Ampere's law and assuming that the plasma is non-isothermal and inhomogeneous, the evolution of the magnetic field diffusion into the plasma is described by the Lienard nonlinear differential equation. Furthermore, it is shown that the departure of the profiles of the magnetic field and electron density variation from a sinusoidal shape in the nonlinear regime and a transverse filamentation and density steepening can occur in the static limit. Also, it is shown that the shape of the transverse filamentation can vary in this regime depending on the gradient of the magnetic field.

Power Spectral Analysis of Enhanced Scintillation of Quasar 3C459 Due to Comet Halley

The radio source 2314+038 (3C459) showed enhanced scintillations on three days at a solar elongation of about 90� as the plasma tail of Halley's Comet swept across it on six days during 16-21 December 1985. If we assume that the plasma velocities in the tail were not constant everywhere, but increased linearly from about 50 kms-1 at the tail axis to the normal average solar wind velocity of 400 kms-1 at the edges where the tail merged with the solar wind, a power spectral analysis of the scintillations shows two ranges of the rms electron density variation t:..N and scale size a. In particular, these are a fine scale zone near the axis where a is in the range 9 to 27 km and t:..N in the range 2 to 5 cm -3 and a zone near the edges with a and t:..N in the ranges 100 to 265 km and 0�4 to 0�8 cm-3 respectively. The assumption of a single velocity of 100 kms-1 throughout the tail shows similar fine scales near the tail axis and large scales near the edges. The scale sizes in that case range from about 18 km at the axis to about 70 km at the edges, corresponding to t:..N of 3�3 and 0�85 cm-3 respectively. A comparison with the results obtained by Slee et al. (1987) shows that there is no radial variation of t:..N. The tail-lag is seen to playa crucial role in determining the correct occulting geometry and the path of the source through the tail.

Enhanced Radio Source Scintillation due to Comet Austin (1989c1)

Enhanced scintillations in the direction of the quasar 2204+29 (3C441) were observed on 13 May 1990 when the tail of Comet Austin passed in front of it. Comparison with previous observations at 103, 327 and 408 MHz of Comet Halley and at 408 MHz of Comet Wilson show that proper occultation geometry is essential for observing enhanced scintillations. It has been shown that the solar elongation ? during such observations should be large, typically greater than 60� and in no case less than 30� at 103 MHz. At the time of the occultation the scintillation index (r.m.s./mean source flux) was greater than that expected for this source by a factor of 3. The r.m.s. electron density variation /IN, at a distance of 0�9 A.U. from the sun and 7�3� downstream of the nucleus, was found to be 6 cm-3 as compared with 1 cm-3 for the normal solar wind at 1 A.U. The corresponding scale sizes of the turbulence were found to be much finer than normally found in interplanetary scintillation (IPS) caused by the solar wind.

Radio Source Scintillations Through Comet Tails Revisited: Comet Wilson (1987)

Observations of the quasars 0606-795 and 0637-752 as the tail of Comet Wilson swept across them on May 1 and May 2, 1987, showed a three-fold increase in scintillation index over that of nearby compact radio sources outside the tail. Two scintillation regimes have been identified: (1) small-scale turbulence of 10-40 km develops near the tail-axis; (2) large-scale turbulence of 90-350 km is present in the off-axis transition region between the tail plasma and solar wind. At a distance 0�12 AU downstream from the nucleus the r.m.s. electron-density variation in these turbules is 4-8 cm-3 on axis and 0�8-1� 7 cm-3 in the transition region between the tail and the solar wind. The reported negative results from earlier comets are shown to be of doubtful significance.