The creation and propagation of longitudinal acoustic phonons (LAPs) in high quality hematite thin films (α-Fe203) epitaxially grown on different substrates (BaTiO3, SrTiO3, and LaAlO3) are investigated using t...The creation and propagation of longitudinal acoustic phonons (LAPs) in high quality hematite thin films (α-Fe203) epitaxially grown on different substrates (BaTiO3, SrTiO3, and LaAlO3) are investigated using the femtosecond pump- probe technique. Transient reflection measurements (AR/R) indicate the photo-excited electron dynamics, and the initial decay less than 1 ps and the slow decay of -500 ps are attributed to the electron-LO phonon coupling and electron-hole nonradiative recombination, respectively. LAPs in α-Fe2O3 film can be created by ultrafast excitation of the ligand field state, such as the ligand field transitions under 800-nm excitation as well as the ligand to metal charge-transfer with 400- nm excitation. The strain modulations of the sound velocity and the out-of-plane elastic properties are demonstrated in α-Fe2O3 film on different substrates.展开更多
Traditional ligand-field theory has to be improved by taking into account both 'pure electronic' contribution and electron-phonon interaction one (including lattice-vibrational relaxation energy). By means of ...Traditional ligand-field theory has to be improved by taking into account both 'pure electronic' contribution and electron-phonon interaction one (including lattice-vibrational relaxation energy). By means of improved ligand-field theory, R1, R2, R'3, R'2, and R'1 lines, U band, ground-state zero-field-splitting (GSZFS), and ground-state g factors of ruby and/or GSGG: Cr3+ as well as thermal shifts of GSZFS, R1 line and R2 line of ruby have been calculated.The results are in very good agreement with the experimental data. Moreover, it is found that the value of cubic-field parameter given by traditional ligand-field theory is inappropriately large. For thermal shifts of GSZFS, R1 line and R2 line of ruby, several conclusions have also been obtained.展开更多
I.THEORY The Hamiltonian of rare earth ions can be written as where (?)<sub>Coul</sub> is the Coulomb interaction, (?)<sub>s·o</sub>, the spin-orbit interaction, (?)<sub>Ca<...I.THEORY The Hamiltonian of rare earth ions can be written as where (?)<sub>Coul</sub> is the Coulomb interaction, (?)<sub>s·o</sub>, the spin-orbit interaction, (?)<sub>Ca</sub>, Casimir operator interaction in the interaction of different configurations in Coulomb interaction, and (?)<sub>cf</sub> is ligand field interaction. A method to treat the rare earth ions is to diagonalize (?)<sub>Coul</sub>, (?)<sub>s.o</sub> and (?)<sub>Ca</sub>, in (1) simultaneously and then to determine the eigenfunction of "展开更多
With the values of parameters obtained from improved ligand-field theory,by taking into account all theirreducible representations and their components in EPI as well as all the levels and the admixtures of basic wave...With the values of parameters obtained from improved ligand-field theory,by taking into account all theirreducible representations and their components in EPI as well as all the levels and the admixtures of basic wavefunc-tions within d^3 electronic configuration,the R-line thermal broadenings(TB)of both MgO:Cr^(3+)and MgO:V^(2+)havemicroscopic-theoretically been calculated.The results are in very good agreement with the experimental data.It is foundthat the R-line TB of MgO:Cr^(3+)or MgO:V^(2+)comes from the first-order term of EPI.The elastic Raman scattering ofacoustic phonons plays a dominant role in R-line TB of MgO:Cr^(3+)or MgO:V^(2+).展开更多
By means of an improved ligand-field theory,the'pure electronic' PS and the PS due to EPI of R line ofMgO:V^(2+) have been calculated,respectively.The calculated results are in very good agreement with the exp...By means of an improved ligand-field theory,the'pure electronic' PS and the PS due to EPI of R line ofMgO:V^(2+) have been calculated,respectively.The calculated results are in very good agreement with the experimentaldata.The behaviors of the pure electronic PS of R line of MgO:V^(2+) and the PS of its R line due to EPI are different.Itis the combined effect of them that gives rise to the total PS of R line,which has satisfactorily explained the experimentalresults.The mixing-degree of [t_2~2(~3T_1)e ~4T_2〉and [t_3~2 ~2E〉 in the wavefunction of R level and its variation with pressurehave been calculated and analyzed.The comparison between the feature of R-line PS of MgO:V^(2+) and that of MgO:Cr^(3+)has been made.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11174195)
文摘The creation and propagation of longitudinal acoustic phonons (LAPs) in high quality hematite thin films (α-Fe203) epitaxially grown on different substrates (BaTiO3, SrTiO3, and LaAlO3) are investigated using the femtosecond pump- probe technique. Transient reflection measurements (AR/R) indicate the photo-excited electron dynamics, and the initial decay less than 1 ps and the slow decay of -500 ps are attributed to the electron-LO phonon coupling and electron-hole nonradiative recombination, respectively. LAPs in α-Fe2O3 film can be created by ultrafast excitation of the ligand field state, such as the ligand field transitions under 800-nm excitation as well as the ligand to metal charge-transfer with 400- nm excitation. The strain modulations of the sound velocity and the out-of-plane elastic properties are demonstrated in α-Fe2O3 film on different substrates.
文摘Traditional ligand-field theory has to be improved by taking into account both 'pure electronic' contribution and electron-phonon interaction one (including lattice-vibrational relaxation energy). By means of improved ligand-field theory, R1, R2, R'3, R'2, and R'1 lines, U band, ground-state zero-field-splitting (GSZFS), and ground-state g factors of ruby and/or GSGG: Cr3+ as well as thermal shifts of GSZFS, R1 line and R2 line of ruby have been calculated.The results are in very good agreement with the experimental data. Moreover, it is found that the value of cubic-field parameter given by traditional ligand-field theory is inappropriately large. For thermal shifts of GSZFS, R1 line and R2 line of ruby, several conclusions have also been obtained.
文摘I.THEORY The Hamiltonian of rare earth ions can be written as where (?)<sub>Coul</sub> is the Coulomb interaction, (?)<sub>s·o</sub>, the spin-orbit interaction, (?)<sub>Ca</sub>, Casimir operator interaction in the interaction of different configurations in Coulomb interaction, and (?)<sub>cf</sub> is ligand field interaction. A method to treat the rare earth ions is to diagonalize (?)<sub>Coul</sub>, (?)<sub>s.o</sub> and (?)<sub>Ca</sub>, in (1) simultaneously and then to determine the eigenfunction of "
基金supported partially by National Natural Science Foundation of China under Grant No.40841012
文摘With the values of parameters obtained from improved ligand-field theory,by taking into account all theirreducible representations and their components in EPI as well as all the levels and the admixtures of basic wavefunc-tions within d^3 electronic configuration,the R-line thermal broadenings(TB)of both MgO:Cr^(3+)and MgO:V^(2+)havemicroscopic-theoretically been calculated.The results are in very good agreement with the experimental data.It is foundthat the R-line TB of MgO:Cr^(3+)or MgO:V^(2+)comes from the first-order term of EPI.The elastic Raman scattering ofacoustic phonons plays a dominant role in R-line TB of MgO:Cr^(3+)or MgO:V^(2+).
文摘By means of an improved ligand-field theory,the'pure electronic' PS and the PS due to EPI of R line ofMgO:V^(2+) have been calculated,respectively.The calculated results are in very good agreement with the experimentaldata.The behaviors of the pure electronic PS of R line of MgO:V^(2+) and the PS of its R line due to EPI are different.Itis the combined effect of them that gives rise to the total PS of R line,which has satisfactorily explained the experimentalresults.The mixing-degree of [t_2~2(~3T_1)e ~4T_2〉and [t_3~2 ~2E〉 in the wavefunction of R level and its variation with pressurehave been calculated and analyzed.The comparison between the feature of R-line PS of MgO:V^(2+) and that of MgO:Cr^(3+)has been made.