The boron carbonyl cation complexes B（CO）3＋, B（CO）4＋ and B2（CO）4＋ are studied by infrared photodissociation spectroscopy and theoretical calculations. The B（CO）4＋ ions are characterized to be very weakly b...The boron carbonyl cation complexes B（CO）3＋, B（CO）4＋ and B2（CO）4＋ are studied by infrared photodissociation spectroscopy and theoretical calculations. The B（CO）4＋ ions are characterized to be very weakly bound complexes involving a B（CO）3＋ core ion, which is predicted to have a planar D3h structure with the central boron retaining the most favorable 8-electron configuration. The B2（C0）4＋ cation is determined to have a planar D2h structure involving a B-B one and half bond. The analysis of the B-CO interactions with the EDA- NOCV method indicates that the OC→B cr donation is stronger than the B-＋CO π back donation in both ions.展开更多
The ultrafast excited state dynamics of trans-4-aminoazobenzene （trans-4-AAB） in ethanol was investigated by femtosecond transient absorption spectroscopy. After being excited to the S2 state by 400 nm, trans-4-AAB ...The ultrafast excited state dynamics of trans-4-aminoazobenzene （trans-4-AAB） in ethanol was investigated by femtosecond transient absorption spectroscopy. After being excited to the S2 state by 400 nm, trans-4-AAB decays from the S2 state to the hot S1 state by internal conversion with time constant of -70 fs. The photoisomerization through inversion mechanism on the S1 potential energy surface and the internal conversion from the S1 state to the hot So state are observed, respectively. The average timescale of these two decay pathways is -0.7 ps. And the vibrational cooling of the hot So state of cis- and trans-4- AAB occur with time constants of -4 and N13 ps, respectively. Furthermore, the ultrafast intersystem crossing process are also observed. The timescale of intersystem crossing from the S2 state to the T4 state is about 480 ps while from the S1 state to the T2 state is -180 ps.展开更多
The excited state structural dynamics of phenyl absorbing S2（A＇）, S3（A＇）, and S6（A＇） states were troseopy and complete active space self-consistent and the UV absorption bands were assigned on azide （PhN3） ...The excited state structural dynamics of phenyl absorbing S2（A＇）, S3（A＇）, and S6（A＇） states were troseopy and complete active space self-consistent and the UV absorption bands were assigned on azide （PhN3） after excitation to the light studied using the resonance Raman specfield calculations. The vibrational spectra the basis of the Fourier transform （FT）- Raman, FT-infrared measurements, the density-functional theory computations and the normal mode analysis. The A-, B-, and C-bands resonance Raman spectra in cyclohex- ane, acetonitrile, and methanol solvents were, respectively, obtained at 273.9, 252.7, 245.9, 228.7, 223.1, and 208.8 nm excitation wavelengths to probe the corresponding structural dynamics of PhN3. The results indicated that the structural dynamics in the S2 （A＇）, S3（A＇）, and S6（A＇） states were significantly different. The crossing points of the potential energy surfaces, S2S1（1） and S2S1（2）, were predicted to play a key role in the low-lying excited state decay dynamics, in accordance with Kasha＇s rule, and NT=N8 dissociation. Two decay channels initiated from the Franck-Condon region of the S2（A＇） state were predicted： the radiative S2,min→S0 radiative decay and the S2→S1 internal conversion through the crossing points S2S1 （1）/S2S1（2）.展开更多
Materials with the formula Yb2-xAlxMo3O12 （x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.9, 1.0, 1.1, 1.3, 1.5, and 1.8） were synthesized and their structures, phase transitions, and hygroscopicity investigated using X-ray po...Materials with the formula Yb2-xAlxMo3O12 （x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.9, 1.0, 1.1, 1.3, 1.5, and 1.8） were synthesized and their structures, phase transitions, and hygroscopicity investigated using X-ray powder diffraction, Raman spectroscopy, and thermal analysis. It is shown that Yb2-xAlxMo3012 solid solutions crystallize in a single monoclinic phase for 1.7 〈 x 〈 2.0 and in a single orthorhombic phase for 0.0 〈 x 〈 0,4, and exhibit the characteristics of both monoclinic and orthorhombic structures outside these compositional ranges. The monoclinic to orthorhonlbic phase transition temperature of A12Mo3012 can be reduced by partial substitution of A13＋ by Yb3＋, and the Yb2-zAlxMo3012 （0.0 〈 x 〈 2.0） materials are hydrated at room temperature and contain two kinds of water species. One of these interacts strongly with and hinders the motions of the polyhedra, while the other does not. The partial substitution of A13＋ for Yb3＋ in Yb2Mo3012 decreases its hygroscopicity, and the linear thermal expansion coefficients after complete removal of water species are measured to be -9.1 x 10-6/K, -5.5 x 10-6/K, 5.74 x 10-6/K, and 9.5 x 10 6/K for Ybl.sAlo.2（MoO4）3, Yb1.6Alo.4（MoO4）3, Ybo.4All.6（Mo04）3, and Ybo.2Al1.8（MoO4）3, respectively.展开更多
Grain-boundary（GB） structures are commonly imaged as discrete atomic columns, yet the chemical modifications are gradual and extend into the adjacent lattices, notably the space charge, hence the two-dimensional def...Grain-boundary（GB） structures are commonly imaged as discrete atomic columns, yet the chemical modifications are gradual and extend into the adjacent lattices, notably the space charge, hence the two-dimensional defects may also be treated as continuum changes to extended interfacial structure. This review presents a spatially-resolved analysis by electron energy-loss spectroscopy of the GB chemical structures in a series of SrTiO3 bicrystals and a ceramic, using analytical electron microscopy of the pre-Cs-correction era. It has identified and separated a transient layer at the model Σ5 grain-boundaries（GBs） with characteristic chemical bonding, extending the continuum interfacial approach to redefine the GB chemical structure. This GB layer has evolved under segregation of iron dopant, starting from subtle changes in local bonds until a clear transition into a distinctive GB chemistry with substantially increased titanium concentration confined within the GB layer in 3-unit cells, heavily strained, and with less strontium. Similar segregated GB layer turns into a titania-based amorphous film in SrTiO3 ceramic, hence reaching a more stable chemical structure in equilibrium with the intergranular Ti2O3 glass also. Space charge was not found by acceptor doping in both the strained Σ5 and amorphous GBs in SrTiO3 owing to the native transient nature of the GB layer that facilitates the transitions induced by Fe segregation into novel chemical structures subject to local and global equilibria. These GB transitions may add a new dimension into the structure–property relationship of the electronic materials.展开更多
A new experimental measurement of residual stresses around Vickers′ indentations on the surface of the SiC/Al 2O 3 nanocomposites is proposed with the aid of a Raman microprobe. Results s how that the shifts of R...A new experimental measurement of residual stresses around Vickers′ indentations on the surface of the SiC/Al 2O 3 nanocomposites is proposed with the aid of a Raman microprobe. Results s how that the shifts of R lines in the fluorescence spectra va ry with the distance from the centre of indentation. The magnitude of load appli ed on the surface of the materials through the indenter influences the shifts of R lines to great extent. The luminescence of R lines of the materials before indenting is used to determine the residual stresses around the indentation in the materials, assuming that the stress tensor is transversely isotropic. Final ly, the term of hydrostatic stress is adopted to explain and compare different residual stresses around indentations with the increase of the indenting load an d the distance from the centre of indentations. <展开更多
Ar/CH3OH and Ar/N2/CH3OH plasma jets were generated at atmospheric pressure by dual-frequency excitations. Two different cases were studied with focus laid on the generation of CN radicals. In one case Ar gas passed t...Ar/CH3OH and Ar/N2/CH3OH plasma jets were generated at atmospheric pressure by dual-frequency excitations. Two different cases were studied with focus laid on the generation of CN radicals. In one case Ar gas passed through a bubbler with saturated methanol steam but without addition of N2 （Ar/CH3OH plasma）. In the other case N2 passed through the bubbler with saturated methanol steam （Ar/N2/CH3OH plasma）. The optical emission lines of CN radicals have been observed in these two cases of plasma discharges. The addition of N2 can significantly increase the optical emission intensity of CN bands.展开更多
The bondstructureofhydrogenated diamond likecarbon( DLC) filmsdeposited with plasmabased ionimplantation ( PBII) wascharacterized by Raman spectroscopy andcore level band and valenceband spectrum of XPS. Theresults...The bondstructureofhydrogenated diamond likecarbon( DLC) filmsdeposited with plasmabased ionimplantation ( PBII) wascharacterized by Raman spectroscopy andcore level band and valenceband spectrum of XPS. Theresultsshow thatthe hydrogenated carbon filmspre pared with lower pulse bias, especially zero bias, display polymer like feature. The DLCfilms deposited with 15 kVpulsebiascontainsthehighestdensityofsp3 bonds. Thecore lev elband ( C1s) spectra of allfilmsshifttowardlow bindingenergy after4kVAr+ ion bom barding. The valenceband spectra of hydrogenated DLCfilmsarequite differentfrom thatof diamond and graphite. However, afterion bombarding, besidetwosingle peaksatabout17 0 eVand 12 5 eV(similarto graphite) ,two new sharp peaksappearatabout21 3 eVand 8 0 eV,respectively. Thepeak at8 0 eVcan beconsidertothecontribution duetothe actingofimplanted argon on C Cbondsand C Hbondsin thefilms.展开更多
A new experimental measurement of residual stresses around Vickers′ indentations on the surface of the SiC/Al 2O 3 nanocomposites is proposed with the aid of a Raman microprobe. Results s how that the shifts of R...A new experimental measurement of residual stresses around Vickers′ indentations on the surface of the SiC/Al 2O 3 nanocomposites is proposed with the aid of a Raman microprobe. Results s how that the shifts of R lines in the fluorescence spectra va ry with the distance from the centre of indentation. The magnitude of load appli ed on the surface of the materials through the indenter influences the shifts of R lines to great extent. The luminescence of R lines of the materials before indenting is used to determine the residual stresses around the indentation in the materials, assuming that the stress tensor is transversely isotropic. Final ly, the term of hydrostatic stress is adopted to explain and compare different residual stresses around indentations with the increase of the indenting load an d the distance from the centre of indentations. 【展开更多
基金The work was supported by the Ministry of Sci- ence and Technology of China （No.2013CB834603） and the National Natural Science Foundation of China （No.21173053 and No.21433005）.
文摘The boron carbonyl cation complexes B（CO）3＋, B（CO）4＋ and B2（CO）4＋ are studied by infrared photodissociation spectroscopy and theoretical calculations. The B（CO）4＋ ions are characterized to be very weakly bound complexes involving a B（CO）3＋ core ion, which is predicted to have a planar D3h structure with the central boron retaining the most favorable 8-electron configuration. The B2（C0）4＋ cation is determined to have a planar D2h structure involving a B-B one and half bond. The analysis of the B-CO interactions with the EDA- NOCV method indicates that the OC→B cr donation is stronger than the B-＋CO π back donation in both ions.
文摘The ultrafast excited state dynamics of trans-4-aminoazobenzene （trans-4-AAB） in ethanol was investigated by femtosecond transient absorption spectroscopy. After being excited to the S2 state by 400 nm, trans-4-AAB decays from the S2 state to the hot S1 state by internal conversion with time constant of -70 fs. The photoisomerization through inversion mechanism on the S1 potential energy surface and the internal conversion from the S1 state to the hot So state are observed, respectively. The average timescale of these two decay pathways is -0.7 ps. And the vibrational cooling of the hot So state of cis- and trans-4- AAB occur with time constants of -4 and N13 ps, respectively. Furthermore, the ultrafast intersystem crossing process are also observed. The timescale of intersystem crossing from the S2 state to the T4 state is about 480 ps while from the S1 state to the T2 state is -180 ps.
基金This work is supported by the National Natural Science Foundation of China （No.21473163, No.21033002, No.21202032） and the National Basic Research Program of China （No.2013CB834604）.
文摘The excited state structural dynamics of phenyl absorbing S2（A＇）, S3（A＇）, and S6（A＇） states were troseopy and complete active space self-consistent and the UV absorption bands were assigned on azide （PhN3） after excitation to the light studied using the resonance Raman specfield calculations. The vibrational spectra the basis of the Fourier transform （FT）- Raman, FT-infrared measurements, the density-functional theory computations and the normal mode analysis. The A-, B-, and C-bands resonance Raman spectra in cyclohex- ane, acetonitrile, and methanol solvents were, respectively, obtained at 273.9, 252.7, 245.9, 228.7, 223.1, and 208.8 nm excitation wavelengths to probe the corresponding structural dynamics of PhN3. The results indicated that the structural dynamics in the S2 （A＇）, S3（A＇）, and S6（A＇） states were significantly different. The crossing points of the potential energy surfaces, S2S1（1） and S2S1（2）, were predicted to play a key role in the low-lying excited state decay dynamics, in accordance with Kasha＇s rule, and NT=N8 dissociation. Two decay channels initiated from the Franck-Condon region of the S2（A＇） state were predicted： the radiative S2,min→S0 radiative decay and the S2→S1 internal conversion through the crossing points S2S1 （1）/S2S1（2）.
基金supported by the National Natural Science Foundation of China (Grant No. 10974183)
文摘Materials with the formula Yb2-xAlxMo3O12 （x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.9, 1.0, 1.1, 1.3, 1.5, and 1.8） were synthesized and their structures, phase transitions, and hygroscopicity investigated using X-ray powder diffraction, Raman spectroscopy, and thermal analysis. It is shown that Yb2-xAlxMo3012 solid solutions crystallize in a single monoclinic phase for 1.7 〈 x 〈 2.0 and in a single orthorhombic phase for 0.0 〈 x 〈 0,4, and exhibit the characteristics of both monoclinic and orthorhombic structures outside these compositional ranges. The monoclinic to orthorhonlbic phase transition temperature of A12Mo3012 can be reduced by partial substitution of A13＋ by Yb3＋, and the Yb2-zAlxMo3012 （0.0 〈 x 〈 2.0） materials are hydrated at room temperature and contain two kinds of water species. One of these interacts strongly with and hinders the motions of the polyhedra, while the other does not. The partial substitution of A13＋ for Yb3＋ in Yb2Mo3012 decreases its hygroscopicity, and the linear thermal expansion coefficients after complete removal of water species are measured to be -9.1 x 10-6/K, -5.5 x 10-6/K, 5.74 x 10-6/K, and 9.5 x 10 6/K for Ybl.sAlo.2（MoO4）3, Yb1.6Alo.4（MoO4）3, Ybo.4All.6（Mo04）3, and Ybo.2Al1.8（MoO4）3, respectively.
基金supported by the National Natural Science Foundation of China(Grant No.51532006)the Fund from Shanghai Municipal Science and Technology Commission(Grant No.16DZ2260600)+1 种基金the 111 Project of the Ministry of Educationthe Fund from the National Bureau of Foreign Experts(Project No.D16002)
文摘Grain-boundary（GB） structures are commonly imaged as discrete atomic columns, yet the chemical modifications are gradual and extend into the adjacent lattices, notably the space charge, hence the two-dimensional defects may also be treated as continuum changes to extended interfacial structure. This review presents a spatially-resolved analysis by electron energy-loss spectroscopy of the GB chemical structures in a series of SrTiO3 bicrystals and a ceramic, using analytical electron microscopy of the pre-Cs-correction era. It has identified and separated a transient layer at the model Σ5 grain-boundaries（GBs） with characteristic chemical bonding, extending the continuum interfacial approach to redefine the GB chemical structure. This GB layer has evolved under segregation of iron dopant, starting from subtle changes in local bonds until a clear transition into a distinctive GB chemistry with substantially increased titanium concentration confined within the GB layer in 3-unit cells, heavily strained, and with less strontium. Similar segregated GB layer turns into a titania-based amorphous film in SrTiO3 ceramic, hence reaching a more stable chemical structure in equilibrium with the intergranular Ti2O3 glass also. Space charge was not found by acceptor doping in both the strained Σ5 and amorphous GBs in SrTiO3 owing to the native transient nature of the GB layer that facilitates the transitions induced by Fe segregation into novel chemical structures subject to local and global equilibria. These GB transitions may add a new dimension into the structure–property relationship of the electronic materials.
文摘A new experimental measurement of residual stresses around Vickers′ indentations on the surface of the SiC/Al 2O 3 nanocomposites is proposed with the aid of a Raman microprobe. Results s how that the shifts of R lines in the fluorescence spectra va ry with the distance from the centre of indentation. The magnitude of load appli ed on the surface of the materials through the indenter influences the shifts of R lines to great extent. The luminescence of R lines of the materials before indenting is used to determine the residual stresses around the indentation in the materials, assuming that the stress tensor is transversely isotropic. Final ly, the term of hydrostatic stress is adopted to explain and compare different residual stresses around indentations with the increase of the indenting load an d the distance from the centre of indentations. <
基金supported by National Natural Science Foundation of China(No.11165012)China Postdoctoral Science Foundation Funded Project(Nos.2011M501494,2012T50831)+1 种基金Project of Key Laboratory of Atomic and Molecular Physics & Functional Materials of Gansu Province,ChinaProject of Northwest Normal University of China(NWNU-LKQN-11-9)
文摘Ar/CH3OH and Ar/N2/CH3OH plasma jets were generated at atmospheric pressure by dual-frequency excitations. Two different cases were studied with focus laid on the generation of CN radicals. In one case Ar gas passed through a bubbler with saturated methanol steam but without addition of N2 （Ar/CH3OH plasma）. In the other case N2 passed through the bubbler with saturated methanol steam （Ar/N2/CH3OH plasma）. The optical emission lines of CN radicals have been observed in these two cases of plasma discharges. The addition of N2 can significantly increase the optical emission intensity of CN bands.
文摘The bondstructureofhydrogenated diamond likecarbon( DLC) filmsdeposited with plasmabased ionimplantation ( PBII) wascharacterized by Raman spectroscopy andcore level band and valenceband spectrum of XPS. Theresultsshow thatthe hydrogenated carbon filmspre pared with lower pulse bias, especially zero bias, display polymer like feature. The DLCfilms deposited with 15 kVpulsebiascontainsthehighestdensityofsp3 bonds. Thecore lev elband ( C1s) spectra of allfilmsshifttowardlow bindingenergy after4kVAr+ ion bom barding. The valenceband spectra of hydrogenated DLCfilmsarequite differentfrom thatof diamond and graphite. However, afterion bombarding, besidetwosingle peaksatabout17 0 eVand 12 5 eV(similarto graphite) ,two new sharp peaksappearatabout21 3 eVand 8 0 eV,respectively. Thepeak at8 0 eVcan beconsidertothecontribution duetothe actingofimplanted argon on C Cbondsand C Hbondsin thefilms.
文摘A new experimental measurement of residual stresses around Vickers′ indentations on the surface of the SiC/Al 2O 3 nanocomposites is proposed with the aid of a Raman microprobe. Results s how that the shifts of R lines in the fluorescence spectra va ry with the distance from the centre of indentation. The magnitude of load appli ed on the surface of the materials through the indenter influences the shifts of R lines to great extent. The luminescence of R lines of the materials before indenting is used to determine the residual stresses around the indentation in the materials, assuming that the stress tensor is transversely isotropic. Final ly, the term of hydrostatic stress is adopted to explain and compare different residual stresses around indentations with the increase of the indenting load an d the distance from the centre of indentations. 【
