MEASUREMENTS OF Fe AND Cu K-Shell IONIZATION CROSS SECTIONS BY SLOW ELECTRON IMPACT

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STUDIES ON LOW ENERGY ION-ATOM COLLISIONS BY MEANS OF ELECTRON-SPECTROSCOPY

We present typical results of studies on autoionizationprocesses produced by low energy ion-atom collisions bymeans of the ejected electron spectroscopy,which havebeen performed by Atomic Physics Group of SophiaUniversity.     

TRY TO EXTRACT THE PREFORMATION PROBABILITY OF α-CLUSTER AT THE SURFACE OF HEAVY NUCLEI BY MEANS OF α-TRANSFER REACTIONS LEADING TO THE CONTINUUM STATES

The method of parametrization of EFR-DWBA overlap integral developed by T.Udagawa and T.Tamura et al.,^[1] is improved. Using the improved method we have fitted the experimental double differential energy spectrum of ⁸Be-cluster coming from the reaction ²⁰⁸Pb (¹²C, ⁸Be) ²¹²Po leading to the continuum states and extracted the preformation probability of α-cluster at the surface of ²¹²Po nucleus. Within the range of calculation error, the result is in agreement with that extracted from fitting the experimental data of α-decay.     

PREPARATION AND TRANSPORT PROPERTIES OF SUPERCONDUCTING BPSCCO THIN FILMS

The perparation of BPSCCO thin films by DC magnetron sputtering is reported. We prepared high mass density target of Bi2Pb0.6Sr2Ca2Cu3O10. By varying the substrate temperature, ratio of Ar and O2 pressure as well as the distance between target and substrate, we were able to optimize the process for c -axis oriented thin films of Bi-Compounds. As deposited films show Tcon at about 95K. These films were examined using the electron-probe microanalysic (EMPA) and X-ray diffraction (XRD). The results of electrical resistivity and Hall effect have been discussed. Hall voltage in the mixed state is strongly nonlinear, showing certain features that suggests that vortex depinning mechanism plays an important role in the Hall effect behaviour.     

EXCITATION OF 5dnd（J=4） AUTOIONIZING STATES OF BARIUM BY MEANS OF MULTISTEP LASER DRIVING PLUS A SUPERRADIATION PROCESS AND MQDT ANALYSIS

In this work.superradiation in found to play an important role to populate the metastable level 6s5d ^1 D2 from which 5dnd(J=4) autoionizing Rydberg series were excited through double-resonant laser driving.Experimental results were analysed using 5-channel quantum defect treatment in which three autoionizing Rydberg series and two open channels were included.     

EXPERIMENTAL STUDY OF EXCITATION AND IONIZATION CROSS SECTIONS OF ATOMS AND MOLECULES BY ELECTRON COLLISIONS

About ten groups over universities and institutes are engaged in thevariety of experimental studies on electron-atom and electron-moleculecollisions in Japan.From works by these groups,two different topics,     

TOPOLOGICAL THEORY OF RELATIONSHIP BETWEEN MOLECULAR STRUCTURE AND ITS PROPERTIES

1.INTRODUCTIONMolecular topological property is an important property.A molecular topo-logical index is an invariant of molecular graph.Since the fist topologicalindex was put forward in 1947 by Wiener,just over 40 different topolo-gical indices have been documented in the literature to date.The theoryof molecular topological indices has become a more effective and simplermethod of studying the relationship between molecular structure and its phys-ical properties,chemical properties and biological activity.     

EXCITATION OF 5dnd(J=4)AUTOIONIZING STATES OF BARIUM BY MEANS OF MULTISTEP LASER DRIVNG PLUS A SUPERRADIATION PROCESS AND MQDT ANALYSIS

In this work,superradiation is found to play an important roleto populate the metastable level 6s5d~1 D_2 from which 5dnd(J=4)autoionizing Rydberg series were excited through double-resonantlaser driving. Experimental results were analysed using 5-channelquantum defect treatment in which three autoionizing Rydbergseries and two open channels were included.     

RESEARCH AND TECHNICAL NOTES ACOUSTIC PROPERTIES OF RIGID CLOSED-CELL PLASTIC FOAMS

Acoustic properties of typical rigid c1osed-cll plastic foams have been studied experimentallyas functions of skeleton materials and cells.Longitudinal sound speed perpendicular to the rise direc-tion for PAPI polyurethane foam can be related to foam density by an equation C_l=aρ~b.Polyurethanefoams present acoustic orthotropy as a result of elongated cells in rise direction.For an air-backedfoam layer in a water-filled pulse tube,phase angles of complex reflection coefficients are always near180°when cell sizes are about 0.5mm.Frequency and temperature dependences of sound speed,as wellas attenuation at audiofrequencies in foams,are governed primarily by properties of skeleton materials.     

VISUALIZATION OF UHF ACOUSTIC TRAVELING WAVEFRONT BY CW LASER:THEORY AND EXPERIMENT OF SPATIAL AND TEMPORAL CORRELATION

Using spatial and temporal information correlation theory which is different from the idea oftraditional stroboscope geometrie imaging formation,we've described how to obtain the opticalphase figure of UHF acoustic traveling wavefront in space by CW laser beam and convert it into anamplitude figure.We've also described that there is temporal frequency spectrum in spatialfrequency spectrum,and summarized the methods to get a 2-D high contrast optical figure ofacoustic traveling wavefront by correct spatial filtering concepts so as to clarify some confusions inusual acoustic imagng formation explanation. The experiment and some interesting results have been obtained.As an example,we've obtainedsuccessful results for 37.5 MHz ultrasonic traveling wave from not only bulk wave but also SAWdevice.The method is in real time and simple.We may expect that it becomes a method thatpromises well in researches on ultrasonic waves.     

ELECTRONIC AND OPTICAL PROPERTIES OF WURTZITE GaN:——A THEORETICAL APPROACH

The band structures of wurtzite GaN(α-GaN) are studied using the nearest and second-nearest neighbour semi-empirical tight-hinding method in sp³ s^* model. The calculated direct fundamental gap of α-GaN is 3.45 eV, which is in good agreement with the experimental data. The density of states and the imaginary pert of dielectric function (ε₂ (ω)) are evaluated to he in the regions - 10.0 - 12 eV and (1.0 - 10.0 eV, respectively. There are mainly three peaks at 6,4, 7,5, 8.4 eV, dominating the ε₂(ω) spectrum. The two components of the ε₂(ω) (i. e. ε_2xy(ω) and ε_2z(ω) ) are also calculated; and the real prat of dielectric function, reflectivity, absorption coefficient, and refractive index are all studied.     

ELECTRONIC AND OPTICAL PROPERTIES OF WURTZITE GaN:——A THEORETICAL APPROACH

The band structures of wurtzite GaN(α-GaN) are studied using the nearest and second-nearest neighbour semi-empirical tight-hinding method in sp³ s^* model. The calculated direct fundamental gap of α-GaN is 3.45 eV, which is in good agreement with the experimental data. The density of states and the imaginary pert of dielectric function (ε₂ (ω)) are evaluated to he in the regions - 10.0 - 12 eV and (1.0 - 10.0 eV, respectively. There are mainly three peaks at 6,4, 7,5, 8.4 eV, dominating the ε₂(ω) spectrum. The two components of the ε₂(ω) (i. e. ε_2xy(ω) and ε_2z(ω) ) are also calculated; and the real prat of dielectric function, reflectivity, absorption coefficient, and refractive index are all studied.     

THE DETERMINATION OF ENDPOINT ENERGY FOR 235Th β-DECAY

Sources of ²³⁵Th were prepared by 14MeV neutron irradiation of Uranium and radiochemical separation.The β-spectra and γ-spectra were measured.The endpoint energy for ²³⁵Th β-decay was obtained to be 1.44±0.04MeV.Thus Q_B of ²³⁵Th was determined to be 1.47±0.07MeV.     

EFFECTS OF HEAT TREATMENT ON STRUCTURE AND PROPERTIES OF ULTRAFINE K—Co—Mo CATTALYSTS

Co-Mo ultrafine particles were prepared by sol-gel method with citric acid as a complexant.The obtained dried gel was calcined in air and argon atmospheres,respectively.After promoting by K2CO3 and sulifiding,the two catalysts were single CoMoO4 crystallites with average size of 60nm.For the sample treated in argon,the main species in the sample were CoMoO3,besides,some Co-MoO4 existed,and the average size was about 20nm.These results indicated that the decomposition of citric acid reduced the CoMoO4 species and decreased the particle size remarkalby.BET measurements showed that,trating the dried gel in argon,the obtained Co-Mo particle and corresxponding sulifded sample possessed a larger surface area.For the sulfided catalysts,MoS2 and EXAFS results indicated that the sulfided sample whose precursor treated in argon possessed smaller average size.The catalytic activity measurement showed that the decrease of the particle sizes resulted in better properties for mixed alcohol synthesis.     

FTIR AND DSC STUDIES OF MECHANICALLY DEFORMED β-PVDF FILMS

Films of semicrystalline poly(vinylidene fluoride) (PVDF) in the β-phase were studied by Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). The main goal of this study was to improve the understanding of the structural changes that occur in β-PVDF during a mechanical deformation process. FTIR spectroscopy was used to examine the structural variations as a function of strain. DSC data allowed measurement of the melting temperatures and enthalpies of the material before and after deformation, providing information about the changes in the crystalline fraction. After the molecular vibrations were assigned to the corresponding vibrational modes, we investigated the energy and intensity variations of these vibrations at different deformations. A reorientation of the chains from perpendicular to parallel to the stress direction was observed to occur in the plastic region. During the deformation, a decrease in the degree of crystallinity of the material was observed, but the thickness of the lamellae did not change significantly.     

TRANSPORT PROPERTIES OF μc-Si:H FILMS PREPARED BY VERY HIGH HYDROGEN-DILUTED SILANE PLASMA

Highly hydrogen-diluted silane plasma is used to fabricate microcrystalline silicon films in a plasma-enhanced chemical vapour deposition system. X-ray diffraction and micro-Raman scattering spectroscopy are utilized to characterize their microstructure properties. Dark conductivity and drift mobility are measured by the travelling wave method. With the decreasing gas flow ratio of silane-to-hydrogen from 2% to 0.2%, the crystalline volume fraction and the drift mobility increase at room temperature. Meanwhile, the dark conductivity increases initially and then decreases. The relationship between the microstructures and transport properties is discussed.     

REFLECTION OF SOUND PULSE BY PLANE INTERFACE BETWEEN AIR AND POROUS MEDIUM

This paper presents a theoretical analysis of the reflection of a sound pulse by the plane interfacebetween air and ideal porous medium.A general expression of impulse response for a pulsed pointsource is derived.The detailed analysis is presented for three special cases:1)source and receiverlocated on a line perpendicular to the interface,semi-infinite media;2)a layer of porous medium;3)semi-infinite media,grazing incidence.In the second case,the problem is solved by consideringthe multi-reflections in the layer of porous medium.Experimental results are compared with the-oretical calculations for a kind of porous material.     

DETERMINATION OF REFLECTION TIME DELAY AND CRITERION OF CORRECT OVERLAP IN ULTRASONIC WAVE VELOCITY MEASUREMENT WITH PEO METHOD

The Pulse-Echo-Overlap method(PEO method)has now been considered as the most adequatemethod for accurate measurement of the absolute value of ultrasonic velocity.For this accurate timemeasurement,it is essential to find the time delay and implement its corrections,e.g.the correction ofreflection time delay,the correction of diffraction time delay,etc.To overcome the inconvenience of thewidely used in practice method of reflection time delay calculation,and its imperfection in theory,a newcalculation procedure of the reflection time delay correction is worked out in this paper,and an experimentaldetermination method for its value by means of double crystal is suggested.This paper further suggests aparameter of the period increment of zero phase shift Δτ_r,and considers it as an experimental constant,whose value is about 1.7 ns in practical applications. Furthermore,this paper suggests a criterion of correct overlap.If the echoes are correctly overlapped,the slope of the curve of the ultrasonic wave tri     

ESSENTIAL WORK OF FRACTURE AND THE PHASE TRANSFORMATION IN β-iPP

The possibility of phase transformation toughening is demonstrated by the example of the β-modification isotactic polypropylene (β-iPP), which undergoes the β–α transformation (i.e., from hexagonal to monoclinic) during mechanical loading. The β–α recrystallization was examined on essential work of fracture (EWF) specimens with two processing conditions. Differential scanning calorimetry and wide-angle x-ray diffraction demonstrate the occurrence of this β–α transformation. Some structural changes can be identified in EWF specimens by using nano-indentation machine. Toughness of the α- and β-iPP is studied and compared with the EWF concept by using static-loaded deeply double-edge-notched tensile specimens. The main effect of the β–α transformation is a large increase in the specific plastic work consumed in the necked zone.     

SOME STATISTICAL PATTERNS OF CHINESE TONE FOR DISYLLABLE AND ITS APPLICATION ON SYNTHESIS OF SPEECH BY RULE

Although the pitch is different in absolute value the pitch contour corresponding to a particularChinese tone should have a similar pattern which is a distinctive feature in speech perception.Thisis an important feature of Chinese language itself. A lot of work on the pitch pattern of Chinese tones has been done,but most of them were onlyqualitative or oversimplified.It is somewhat difficult to apply those results directly to design ofspeech synthesis by rule.This paper has given 15 new statistical results of tone patterns of Chinesedisyllable and each pattern can be formulated simply by a normalized function P(t)in time domainwhich is directly proportional to T_0_(max) and inversely proportional to T_0(t),where T_0_(max) is thereciprocal of the lowest fundamental frequency in the syllable and T_0(t)the pitch period at time t. It has been shown that there are some characteristics in tone pattern of Chinese disyllable: (l) At the beginning and the end of every tone pattern there is always a transient proc