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1991 Volume 7 Issue 2
1991, 7(02): 129-135
doi: 10.3866/PKU.WHXB19910201
Abstract:
The homogenous gas phase pyrolysis of ethyl acetamide is studied by MINDO/3 molecular orbital method.The results show that the major process proceeds via a six membered ring transition state (TS), but the four membered ring TS is also feasible, which is not accessible in the gas phase pyrolysis of esters. A detail analysis of Intrinsic Reaction Coordinate(IRC) is used to elucidate the reaction mechanism. The results also reveal that the change of activation energy in the polar solvent is not evident, in other words, the catalysis by carboxylic acid is not marked for the gas phase pyrolysis of ethyl acetamide.
The homogenous gas phase pyrolysis of ethyl acetamide is studied by MINDO/3 molecular orbital method.The results show that the major process proceeds via a six membered ring transition state (TS), but the four membered ring TS is also feasible, which is not accessible in the gas phase pyrolysis of esters. A detail analysis of Intrinsic Reaction Coordinate(IRC) is used to elucidate the reaction mechanism. The results also reveal that the change of activation energy in the polar solvent is not evident, in other words, the catalysis by carboxylic acid is not marked for the gas phase pyrolysis of ethyl acetamide.
1991, 7(02): 136-139
doi: 10.3866/PKU.WHXB19910202
Abstract:
We have reported the structure of β-cyanoethyf-a-ferrocenylfluorobenzyl ether. Present study is concerned with the crystal and molecular structures of serious β-cyanoethyl-α-ferrocenylhalogenbenzyl ethers (C_5H_5FeC_5H_4CH (OCH_2CH_2CN)C_6H_4X) (X = F, Cl, Br, I). All crystals were solved with direct method and fourier synthesis. The differences of the structures caused by the different halogen atoms are discussed.
The results have shown there are two types of molecular configuration. A for X=F and B for X=Cl, Br, I.
We have reported the structure of β-cyanoethyf-a-ferrocenylfluorobenzyl ether. Present study is concerned with the crystal and molecular structures of serious β-cyanoethyl-α-ferrocenylhalogenbenzyl ethers (C_5H_5FeC_5H_4CH (OCH_2CH_2CN)C_6H_4X) (X = F, Cl, Br, I). All crystals were solved with direct method and fourier synthesis. The differences of the structures caused by the different halogen atoms are discussed.
The results have shown there are two types of molecular configuration. A for X=F and B for X=Cl, Br, I.
1991, 7(02): 140-145
doi: 10.3866/PKU.WHXB19910203
Abstract:
In the present investigation the theory and method to describe the MO's bonding ability with the Hellmann-Feynman electrostatic force are presented, the MO's bonding effects on a certain chemical bond are described according to the two viewpoints ——energy gradient and electrostatic force. The Mo's bonding properties can be reflected by two aspects of the H-F force vector, size and direction. The same MO has different chemical bonding abilities to different chemical bonds, MO's H-F force of ethylene and cyclopropane are calculated with the ab initio calculation program ABHF, the bonding properties are analysed. The relation between the H-F force and the MO's irreducible representation is presented, a method to decide the molecular geometric configuration variation of excited states by the frontier MO's H-F force is suggested.
In the present investigation the theory and method to describe the MO's bonding ability with the Hellmann-Feynman electrostatic force are presented, the MO's bonding effects on a certain chemical bond are described according to the two viewpoints ——energy gradient and electrostatic force. The Mo's bonding properties can be reflected by two aspects of the H-F force vector, size and direction. The same MO has different chemical bonding abilities to different chemical bonds, MO's H-F force of ethylene and cyclopropane are calculated with the ab initio calculation program ABHF, the bonding properties are analysed. The relation between the H-F force and the MO's irreducible representation is presented, a method to decide the molecular geometric configuration variation of excited states by the frontier MO's H-F force is suggested.
1991, 7(02): 146-151
doi: 10.3866/PKU.WHXB19910204
Abstract:
OAP can be electropolymerized into an uniform film of active POAP in acid solution. The films formed in different acid solutions have compact or open structures. The main structure of the POAP film is (A), The POAP film can be complexed with Ni~(2+) to form POAP-Ni~(2+) film in which the main structure is (B).
OAP can be electropolymerized into an uniform film of active POAP in acid solution. The films formed in different acid solutions have compact or open structures. The main structure of the POAP film is (A), The POAP film can be complexed with Ni~(2+) to form POAP-Ni~(2+) film in which the main structure is (B).
1991, 7(02): 152-157
doi: 10.3866/PKU.WHXB19910205
Abstract:
The potential windows of the system water/pure solvent (W/P) and water/solvent mixtures(W/S) have been investigated by cyclic voltammetry with solvents whose dielectric constants lie between 5.67 and 34.82. In the presence of LiCl in the aqueous phase and tetrabutytammoniumtetraphenylborate(TBATPB) in the organic phase, the systems water/allyl iso-thiocyanate (W/AIT) and water/nitrobenzene (W/NB) show a same wide potential window. Thermodynamic parameters of ion transfer across W/AIT interface were determined. In systems of W/P and W/S the influence solvent effect on the standard Gibbs energies of transfer of ion Δ_o~wG_(tr,i)~p was discussed.
The potential windows of the system water/pure solvent (W/P) and water/solvent mixtures(W/S) have been investigated by cyclic voltammetry with solvents whose dielectric constants lie between 5.67 and 34.82. In the presence of LiCl in the aqueous phase and tetrabutytammoniumtetraphenylborate(TBATPB) in the organic phase, the systems water/allyl iso-thiocyanate (W/AIT) and water/nitrobenzene (W/NB) show a same wide potential window. Thermodynamic parameters of ion transfer across W/AIT interface were determined. In systems of W/P and W/S the influence solvent effect on the standard Gibbs energies of transfer of ion Δ_o~wG_(tr,i)~p was discussed.
1991, 7(02): 158-162
doi: 10.3866/PKU.WHXB19910206
Abstract:
Ni(Ⅱ) ion is complexed by poly-8-hydroxyquinoline, poly-0-aminophenol, poly-0-diaminobenzene and polyaniline as ligands. The voltammograms for the polymer-Ni (Ⅱ) film electrode show well defined reduction and oxidation peaks. They have similar electrochemical properties. Poly-8-hydroxyquinoline film, poly-0-aminophenol film and poly-0-diaminobenzene film can be used to exchange Ni (Ⅱ) with H~+ ion and to separate Ni(Ⅱ), Co (Ⅱ) and Fe(Ⅱ) ions.
Ni(Ⅱ) ion is complexed by poly-8-hydroxyquinoline, poly-0-aminophenol, poly-0-diaminobenzene and polyaniline as ligands. The voltammograms for the polymer-Ni (Ⅱ) film electrode show well defined reduction and oxidation peaks. They have similar electrochemical properties. Poly-8-hydroxyquinoline film, poly-0-aminophenol film and poly-0-diaminobenzene film can be used to exchange Ni (Ⅱ) with H~+ ion and to separate Ni(Ⅱ), Co (Ⅱ) and Fe(Ⅱ) ions.
1991, 7(02): 163-168
doi: 10.3866/PKU.WHXB19910207
Abstract:
By electrochemical polymerization of pyrrole in phosphate buffer, glucose oxidase ( D) was entrapped in polypyrrole matrix (PPy) to construct the enzyme electrode. Effects of electropolymerization conditions, such as pH values and electrode potentials, on the enzyme immobilization were studied. Behavior of D/PPy membranes was characterized by IR and a.c. impedance spectra. The immobilization of D will be accomplished only if pH>5.5. It is likely that D enters into PPy in its entity with negative charge. Spectra of a.c. impedance show that the enzyme electrode has the features similar to porous electrodes. It was edmonstrated that the simultaneous immobilization of D and mediator Fe(CN)_6~(3-) is feasible. The electrcchemically immobilized D maintains its biocatalytic activeties, and apparently the enzymatic reaction follows Michaelis-Menten kinetics.
By electrochemical polymerization of pyrrole in phosphate buffer, glucose oxidase ( D) was entrapped in polypyrrole matrix (PPy) to construct the enzyme electrode. Effects of electropolymerization conditions, such as pH values and electrode potentials, on the enzyme immobilization were studied. Behavior of D/PPy membranes was characterized by IR and a.c. impedance spectra. The immobilization of D will be accomplished only if pH>5.5. It is likely that D enters into PPy in its entity with negative charge. Spectra of a.c. impedance show that the enzyme electrode has the features similar to porous electrodes. It was edmonstrated that the simultaneous immobilization of D and mediator Fe(CN)_6~(3-) is feasible. The electrcchemically immobilized D maintains its biocatalytic activeties, and apparently the enzymatic reaction follows Michaelis-Menten kinetics.
1991, 7(02): 169-173
doi: 10.3866/PKU.WHXB19910208
Abstract:
A equation between the thermodynamic properties and the retention values of capillary gas chromatography was proposed. The thermodynamic properties of nitromethylaniline isomers on cros3linking SE-30, SE-54 and noncrosslinking SE-54 fused silica capillary columns have been calculated and the results were interpreted qualitatively.
A equation between the thermodynamic properties and the retention values of capillary gas chromatography was proposed. The thermodynamic properties of nitromethylaniline isomers on cros3linking SE-30, SE-54 and noncrosslinking SE-54 fused silica capillary columns have been calculated and the results were interpreted qualitatively.
1991, 7(02): 174-177
doi: 10.3866/PKU.WHXB19910209
Abstract:
In this paper, the total energies and band structures of polydiacetylenes(acetylenic structure and butatrienic structure) are calculated by use of LCAO-SCF ab initio crystal orbital (CO) method. The energetic stability and the band structures of the different structures of polydiacetylenes are discussed and analyzed. The influence of side groups on the energies and band structures of polydiacetylenes is also discussed.
In this paper, the total energies and band structures of polydiacetylenes(acetylenic structure and butatrienic structure) are calculated by use of LCAO-SCF ab initio crystal orbital (CO) method. The energetic stability and the band structures of the different structures of polydiacetylenes are discussed and analyzed. The influence of side groups on the energies and band structures of polydiacetylenes is also discussed.
1991, 7(02): 178-183
doi: 10.3866/PKU.WHXB19910210
Abstract:
In this work, expressions for the steady state voltammetric curve of a microdisk electrode are derived by using "uniform concentration" approach. For reversible electrode reactions, the derived expression is exact, while for irreversible and quasireversible reactions, the expressions are approximate.In the case of irreversible reaction, the maximum relative error of the current calculated from the given expression is about 4%. The approximate expression has the form similar to those for conventional planar electrodes. The relation between the upper limit of measurable rate constant and the radius of microdisk electrode is also discussed.
In this work, expressions for the steady state voltammetric curve of a microdisk electrode are derived by using "uniform concentration" approach. For reversible electrode reactions, the derived expression is exact, while for irreversible and quasireversible reactions, the expressions are approximate.In the case of irreversible reaction, the maximum relative error of the current calculated from the given expression is about 4%. The approximate expression has the form similar to those for conventional planar electrodes. The relation between the upper limit of measurable rate constant and the radius of microdisk electrode is also discussed.
1991, 7(02): 184-190
doi: 10.3866/PKU.WHXB19910211
Abstract:
The oscillatary behavior of diacetone alcohol(DA)-KIO_3-H_2O_2-H_2SO_4-Ce~(3+) system has been studied.The system may oscillate in the concentration ranges of H_2SO_4 0.11—0.24, KIO_3 0.019—0.048; Ce~(3+) 5.95×10~(-4)—3.57×10~(-3), DA 0.4—3.22 and H_2O_2 0.40—1.99 mol·dm~(-3) respectively.
Using Hg_2SO_4 electrode as the reference electrode, the potential of I~- and the redox potential show oscillatary wave behavior in XWT balance recorder.
According to our expreimental results, We may said seen that ...
The oscillatary behavior of diacetone alcohol(DA)-KIO_3-H_2O_2-H_2SO_4-Ce~(3+) system has been studied.The system may oscillate in the concentration ranges of H_2SO_4 0.11—0.24, KIO_3 0.019—0.048; Ce~(3+) 5.95×10~(-4)—3.57×10~(-3), DA 0.4—3.22 and H_2O_2 0.40—1.99 mol·dm~(-3) respectively.
Using Hg_2SO_4 electrode as the reference electrode, the potential of I~- and the redox potential show oscillatary wave behavior in XWT balance recorder.
According to our expreimental results, We may said seen that ...
1991, 7(02): 191-195
doi: 10.3866/PKU.WHXB19910212
Abstract:
The structure of the product from the [2+2] photocycloaddition of acetylacetone to methyl 1-naphthoate was determined by X-ray crystallography. Crystal data. C_(17)H_(18)O_4, triclinic, P_1~-, a=0.7401(1), b=0.7656(1), c=1.3882(1) nm, α=84.75(1), β=86.49(1), γ=65.08(1)°, V=0.7102 nm, Z=2, D_c=1.339 g·cm~(-3), μ(MoK_a)=1.0 cm~(-1), F(000)=304. The structure was solved by direct methods and refined to final R=0.049 for 2442 MoKa reflections. The particular bridged structure of the product molecule indicates a [2+2+2] intramolecular cycloaddition in succession to the primary [2+2] photocycloaddition. Molecular mechanics calculations confirmed further that the molecular structure of the ultimate product takes a configuration of comparatively favourable steric energy even though the bridged structure itself is rather strained.
The structure of the product from the [2+2] photocycloaddition of acetylacetone to methyl 1-naphthoate was determined by X-ray crystallography. Crystal data. C_(17)H_(18)O_4, triclinic, P_1~-, a=0.7401(1), b=0.7656(1), c=1.3882(1) nm, α=84.75(1), β=86.49(1), γ=65.08(1)°, V=0.7102 nm, Z=2, D_c=1.339 g·cm~(-3), μ(MoK_a)=1.0 cm~(-1), F(000)=304. The structure was solved by direct methods and refined to final R=0.049 for 2442 MoKa reflections. The particular bridged structure of the product molecule indicates a [2+2+2] intramolecular cycloaddition in succession to the primary [2+2] photocycloaddition. Molecular mechanics calculations confirmed further that the molecular structure of the ultimate product takes a configuration of comparatively favourable steric energy even though the bridged structure itself is rather strained.
1991, 7(02): 196-201
doi: 10.3866/PKU.WHXB19910213
Abstract:
The structure of the product from photodimerization in non-polar solvent of acetylacetone, C_(10)H_(16)O_4, Mr=200.2, was determined from three-dimensional X-ray data. It crystallizes in the monoclinic, space group P2_1/c, a=1.6766(2), b=0.7736(2), c=1.1024(l) nm, β=130.44(2)°, V=1.0882 nm, Z=4, D_o=1.23, D_c=1.222 g·cm~(-3), μ(MoK_a) =0.877 cm~(-1), F(000) =432. The structure was solved by direct methods and refined to R=0.040 for 1861 observed MoK_a reflections. The ultimate product is a furanoid derivative which has a minimum steric energy according to the molecular mechanics calculations. Possible reaction pathway of the photocycloaddition was also discussed.
The structure of the product from photodimerization in non-polar solvent of acetylacetone, C_(10)H_(16)O_4, Mr=200.2, was determined from three-dimensional X-ray data. It crystallizes in the monoclinic, space group P2_1/c, a=1.6766(2), b=0.7736(2), c=1.1024(l) nm, β=130.44(2)°, V=1.0882 nm, Z=4, D_o=1.23, D_c=1.222 g·cm~(-3), μ(MoK_a) =0.877 cm~(-1), F(000) =432. The structure was solved by direct methods and refined to R=0.040 for 1861 observed MoK_a reflections. The ultimate product is a furanoid derivative which has a minimum steric energy according to the molecular mechanics calculations. Possible reaction pathway of the photocycloaddition was also discussed.
1991, 7(02): 202-206
doi: 10.3866/PKU.WHXB19910214
Abstract:
The concept of fractal was applied to interpret the surface of porous solids and the processes proceeded on them. The fractal dimensions were determined from the saturation coverage with different adsorbates.The number of molecules reaching mon olayer coverage scale down with increasing σ as
N～σ~(-D/2)
where σ is the cross section of the probe molecule.
As the porous materials (such as porous silica gel, alumina) were mixed with a few of other active components (Zn(Ac)_2, CuCl_2), it is found that the fractal ...
The concept of fractal was applied to interpret the surface of porous solids and the processes proceeded on them. The fractal dimensions were determined from the saturation coverage with different adsorbates.The number of molecules reaching mon olayer coverage scale down with increasing σ as
N～σ~(-D/2)
where σ is the cross section of the probe molecule.
As the porous materials (such as porous silica gel, alumina) were mixed with a few of other active components (Zn(Ac)_2, CuCl_2), it is found that the fractal ...
1991, 7(02): 207-210
doi: 10.3866/PKU.WHXB19910215
Abstract:
In this paper we used the flowing-afterglow technique to study the energy transfer processes in the reaction of metastable atoms Ar, Ne, and He with CCl_4 and CBr_4, The emission spectra of excited fragments CCl (A—X), Cl_2~* and Br_2~* were obtained. The reaction mechanism were discussed.
In this paper we used the flowing-afterglow technique to study the energy transfer processes in the reaction of metastable atoms Ar, Ne, and He with CCl_4 and CBr_4, The emission spectra of excited fragments CCl (A—X), Cl_2~* and Br_2~* were obtained. The reaction mechanism were discussed.
1991, 7(02): 211-214
doi: 10.3866/PKU.WHXB19910216
Abstract:
The excited fragments CH(A), CH(B), CH(C) etc. were produced by the bombardment of He(2~3S) with CH_nX_(4-n)(X=Cl, Br, I). Based on the CH(A-X) emission spectra, the rotational populations can be interpretated in terms of Boltzmann distribution. The effective rotational temperature for CH(A,v'=0) produced from various methyl halides are nearly the some. Experiments under various pressure and calculation of collisional dynamics showed that the distributions are approximate to the nascent distributions.
The excited fragments CH(A), CH(B), CH(C) etc. were produced by the bombardment of He(2~3S) with CH_nX_(4-n)(X=Cl, Br, I). Based on the CH(A-X) emission spectra, the rotational populations can be interpretated in terms of Boltzmann distribution. The effective rotational temperature for CH(A,v'=0) produced from various methyl halides are nearly the some. Experiments under various pressure and calculation of collisional dynamics showed that the distributions are approximate to the nascent distributions.
1991, 7(02): 215-218
doi: 10.3866/PKU.WHXB19910217
Abstract:
The structure defect of electrodeposited tin was investigated by means of positron annihilation lifetime spectroscopy. It was observed that when annealing temperatures were less than 120 ℃, the vacancies aggregated into a cluster; in the region of 120 —160 ℃, the structure defects changed considerably, some vacancy cluster enlarged and some shrunk due to thermal migration of the atoms; the recrystallization of deposits took place in temperature of 180 ℃, in this case the positrons were premarily annihilated in the expanded crystal boundary.
1991, 7(02): 219-222
doi: 10.3866/PKU.WHXB19910218
Abstract:
Fast atom bombardment mass spectra of a series of arenediazonium salts with various substituents complexed with 18-crown-6 and dibenzo-24-crown-8 ethers were examined. The correlation between quasi-molecular ion abundance of various complexes and the properties, coordination ability of donor-acceptor linkages in the complexes were studied. By using molecular orbital calculation we have successfully demonstrated that the correlation cited is related to the electron cloud densities on the heteroatoms α-N and β-N of arenediazonium salts.
Fast atom bombardment mass spectra of a series of arenediazonium salts with various substituents complexed with 18-crown-6 and dibenzo-24-crown-8 ethers were examined. The correlation between quasi-molecular ion abundance of various complexes and the properties, coordination ability of donor-acceptor linkages in the complexes were studied. By using molecular orbital calculation we have successfully demonstrated that the correlation cited is related to the electron cloud densities on the heteroatoms α-N and β-N of arenediazonium salts.
1991, 7(02): 223-226
doi: 10.3866/PKU.WHXB19910219
Abstract:
This paper reports the results of the crystal and molecular structures, CI-MS and FAB-MS analyse of Cl_3GeCH_2CH_2COOH and Cl_3GeCH(CH_3)CH_2COOH. The characters and active parts of these molecules are also discussed.
This paper reports the results of the crystal and molecular structures, CI-MS and FAB-MS analyse of Cl_3GeCH_2CH_2COOH and Cl_3GeCH(CH_3)CH_2COOH. The characters and active parts of these molecules are also discussed.
1991, 7(02): 227-230
doi: 10.3866/PKU.WHXB19910220
Abstract:
The chlorination reaction of Li_2CO_3 with NH_4Cl has been studied in detail by a series of thermal analysis methods. When NH_4Cl/Li_2CO_3 mole ratio equals 4, Li_2CO_3 can be transformed into LiCl quantitatively in a stream of Ar gas flow. All residual NH_4Cl is decomposed completely at 400 ℃ and carried away from the reaction cell by Ar gas.Analysis by X-Ray diffraction and Ion Chromatography show that there are almost no NH_4Cl remained in The LiCl product. It is interested that the chlorination reaction can be applied to the determinations of phase diagram by thermal analysis method and the preparation of Al-Li alloy by electrolysis in molten salt.
The chlorination reaction of Li_2CO_3 with NH_4Cl has been studied in detail by a series of thermal analysis methods. When NH_4Cl/Li_2CO_3 mole ratio equals 4, Li_2CO_3 can be transformed into LiCl quantitatively in a stream of Ar gas flow. All residual NH_4Cl is decomposed completely at 400 ℃ and carried away from the reaction cell by Ar gas.Analysis by X-Ray diffraction and Ion Chromatography show that there are almost no NH_4Cl remained in The LiCl product. It is interested that the chlorination reaction can be applied to the determinations of phase diagram by thermal analysis method and the preparation of Al-Li alloy by electrolysis in molten salt.
1991, 7(02): 231-233
doi: 10.3866/PKU.WHXB19910221
Abstract:
The isomerization reaction of hydroxylamine H_2NOH rearrangement to ammonia oxide H_3NO was investigated by ab initio MO calculations using RHF/4-31G basis set. The energy gradient method was used to optimize the equilibrium geometries of H_2NOH, H_3NO and the transition state. The activation enthalpy, activation energy, frequency factor, free energy of activation , reaction rate constant and equilibrium constant were calculated. The reaction er dography was analyzed by means of intrinsic reaction coordinate (IRC) method. The vibrational analyses of H_2NOH, H_3NO, and the reaction coordinate have been made by the numerical differentiation method. The vibrational frequency correlation diagram along the IRC has been plotted and a vibrational excited state of OH bond is anticipated before the transition state.
The isomerization reaction of hydroxylamine H_2NOH rearrangement to ammonia oxide H_3NO was investigated by ab initio MO calculations using RHF/4-31G basis set. The energy gradient method was used to optimize the equilibrium geometries of H_2NOH, H_3NO and the transition state. The activation enthalpy, activation energy, frequency factor, free energy of activation , reaction rate constant and equilibrium constant were calculated. The reaction er dography was analyzed by means of intrinsic reaction coordinate (IRC) method. The vibrational analyses of H_2NOH, H_3NO, and the reaction coordinate have been made by the numerical differentiation method. The vibrational frequency correlation diagram along the IRC has been plotted and a vibrational excited state of OH bond is anticipated before the transition state.
1991, 7(02): 234-237
doi: 10.3866/PKU.WHXB19910222
Abstract:
XPS inner shell. satellite peaks and its valence band spectra of the pyridoxygen complexes of rare earth decahydrodecaborate nave been investigated. The binding energies of the ligand atoms show variation with increasing atomic number of rare earth elements and a specific "tetrad effect" is observed in the plot of binding energies of ligand atoms versus rare earth atomic numbers. The XPS valence band spectra of different rare earth complexes are characteristic for the rare earth elements.
XPS inner shell. satellite peaks and its valence band spectra of the pyridoxygen complexes of rare earth decahydrodecaborate nave been investigated. The binding energies of the ligand atoms show variation with increasing atomic number of rare earth elements and a specific "tetrad effect" is observed in the plot of binding energies of ligand atoms versus rare earth atomic numbers. The XPS valence band spectra of different rare earth complexes are characteristic for the rare earth elements.
1991, 7(02): 238-241
doi: 10.3866/PKU.WHXB19910223
Abstract:
Photocurrent spectra and photoluminescence measurements of the electrode covered by a thin film of chromium tetra-2,3-pyridinoporphyrazine by conventional 3-electrode system method have been performed. The cathodic photocurrent has been measured. The shape of the photocurrent spectrum is similar to that of photoluminescence spectrum. Their intensities change as a function of the applied potential. Two photoluminescence peaks are located at about 470 nm and 520 nm. The results indicate that the thin film behaves like a p-type semiconductor with a band gap width of about 2 eV.
Photocurrent spectra and photoluminescence measurements of the electrode covered by a thin film of chromium tetra-2,3-pyridinoporphyrazine by conventional 3-electrode system method have been performed. The cathodic photocurrent has been measured. The shape of the photocurrent spectrum is similar to that of photoluminescence spectrum. Their intensities change as a function of the applied potential. Two photoluminescence peaks are located at about 470 nm and 520 nm. The results indicate that the thin film behaves like a p-type semiconductor with a band gap width of about 2 eV.
1991, 7(02): 242-245
doi: 10.3866/PKU.WHXB19910224
Abstract:
On basis of ab initio quantum chemical calculations formulas for calculating screening constants σ_(ji) and orbital radius parameters r_(p,i) (used for expressing the penetrating effect) have been established. The rules of penetrating and screening effects have been modified: (1) For 3d and 4d transition elements the (n-1)d orbitals penetrate more deeply than the ns, where n denotes the principal quantum number of the outermost shell; for RE atoms 4f penetrates more deeply than 6s. (2) The screening constants between electrons in the same sub-shell is rather large, 0.65-0.7. (3) The screening constants of the outermost shell electron to that of the next out are not negligible, 0.3-0.4. Some difficulties in the theory of the atomic structure principle may thus be overcome.
On basis of ab initio quantum chemical calculations formulas for calculating screening constants σ_(ji) and orbital radius parameters r_(p,i) (used for expressing the penetrating effect) have been established. The rules of penetrating and screening effects have been modified: (1) For 3d and 4d transition elements the (n-1)d orbitals penetrate more deeply than the ns, where n denotes the principal quantum number of the outermost shell; for RE atoms 4f penetrates more deeply than 6s. (2) The screening constants between electrons in the same sub-shell is rather large, 0.65-0.7. (3) The screening constants of the outermost shell electron to that of the next out are not negligible, 0.3-0.4. Some difficulties in the theory of the atomic structure principle may thus be overcome.
1991, 7(02): 246-255
doi: 10.3866/PKU.WHXB19910225
Abstract:
