نشریه علوم پایه
سال بیست و دوم شماره 1 (1388)

We study in this paper the resonance production, by using the electron annihilation data in 60 Ge V centre of mass energy. To achieve this we make a plot of the effective mass distributions for all combinations in an event. Then we fit this distribution by using Breit – Wigner formula. We observe that approximately 8% of the events come from the decay. Thus a correction should be made when investigating the particles coming straight from the primary vertex. These corrections are due to the particles which originate from the resonance decay. By dividing the events into the forward and backward regions, we observe that the cross section for production is equal in the two regions.

In this paper, the fabrication of a double-pulse copper chloride laser was investigated to study the effect of various parameters such as buffer gas pressure, temperature, and the delay time between two electrical discharge pulses, on laser output power. Moreover, a single-pulse copper bromide laser was fabricated to optimize the laser output power versus temperature, buffer gas pressure, and electrical input power and discharge frequency. The comparison of the results in single-pulse and double-pulse excitation indicates that the former is easier in operation and more power stability can be achieved using single pulse excitation.

Acetylene (C2H2) is a linear quadratic molecule and an example of C – C with triple band in chemistry that The structure of acetylene molecule has 7 normal vibrational modes. Rovibrational absorption spectrum in the IR region of this molecule is detected in the outer atmosphere of the earth. It plays an important role in intermolecular studies. this molecular is include two important isotoper that in this paper we study on 1000cm-1 to 10000cm-1 for the isotope C2HD. Energy expansion coefficients for series of stretch-vibration bands of some combination tones is calculated and approximated. At the end, the study of prediction of intensity and comparison to experimental intensity is done too In this paper we try to describe our experimental or theoretical results.

The curved microchannel plates (MCP), are the ones which are the same as disks. So millions of channels are created into them. Each channel has a role of electron multiplier. These plates are placed in vicinity of the photocathode in a way that the emission of photoelectrons from photocathode under the influence of the potential difference, enter the channels and strike the walls the secondary electrons are emitted, in turn generate further secondaries. The channel thus acts like a miniature photomultiplier tube. These plates have two basic characteristics such as high gain and low Ion feedback.Here, we numerically investigate a method to improve the gain of an electron multiplier by changinhg the geometry of channels. In our geometry, however, instead of straight channels we consider curved channels. This curvature produce interesting physical effects on MCP. It indicates increase gain and decrease Ion feedback. Also a decrease of Ion feedback caused a decrease noise of system. Finally we computed the gain of electron emission and ploted gain versus various angles and compared our results with the other work.

In the paperEnergy band structure and total density of state of and in tetragonal phase are Calculated by using WIEN2k Code.In ab initio calculations based on density functional theory(DFT) the full potential – linearized augmented plan wave (FP–LAPW) and the generalized gradient approximation(GGA) used. The calculated band structure and density of states of two materials agree with the previous experimental and theoretical results.This calculation in order to better understand the origin of the ferroelectric instability in perovskites and reasons for different ferroelectric behavior in the two materials.The differences in behavior between BaTiO3 and stem from their different electronic structures:The Pb6s and O 2p states are strongly hybridized in, whereas Ba is essentially a fully ionic ion in BaTiO3.In both materials the Ti3d states hybridize with O 2p, and it is the Ti-O interaction that is responsible for the ferroelectric instability.

In this article, on the basis of the quark model, we consider from factors for mesons and thereby we study the charge radius of mesons. We also obtain the exact analytical solution of the Schrodinger equation for our two-body system in the presence of color charge and oscillating potentials.On the other hand, as quark Rave spin, we consider the effects of spin-spin and spin-isospin interactions as perturbations and thereby calculate the first-order energy shift.

One of the main problems which are involved in many physical processes is the difference of energy state between ground state and first excited state for potential wells. This is generally solved by using the approximation methods. In this paper, we calculate these difference values for a five fold and seven fold potential wells using Supersymmetry in Quantum Mechanics(SUSYQM). We finally generalize it to find a relation for (2n+1)-fold wells.