By means of both a theory for pressure-induced shifts (PS) of energy spectra and a theory for shifts of energy spectra due to electron-phonon interaction (EPI), the 'pure electronic' PS and the PS due to EPI o...By means of both a theory for pressure-induced shifts (PS) of energy spectra and a theory for shifts of energy spectra due to electron-phonon interaction (EPI), the 'pure electronic' PS and the PS due to EPI of R<SUB>1</SUB> line, R<SUB>2</SUB> line, and U band of GSGG:Cr<SUP>3+</SUP> at 300 K have been calculated, respectively. The calculated results are in good agreement with all the experimental data. Their physical origins have also been explained. It is found that the mixing-degree of and base-wavefunctions in the wavefunctions of R<SUB>1</SUB> level of GSGG:Cr<SUP>3+</SUP> at 300 K is remarkable under normal pressure, and the mixing-degree rapidly decreases with increasing pressure. The change of the mixing-degree with pressure plays a key role not only for the 'pure electronic' PS of R<SUB>1</SUB> line and R<SUB>2</SUB> line but also the PS of R<SUB>1</SUB> line and R<SUB>2</SUB> line due to EPI. The pressure-dependent behaviors of the 'pure electronic' PS of R<SUB>1</SUB> line (or R<SUB>2</SUB> line) and the PS of R<SUB>1</SUB> line (or R<SUB>2</SUB> line) due to EPI are quite different. It is the combined effect of them that gives rise to the total PS of R<SUB>1</SUB> line (or R<SUB>2</SUB> line). In the range of about 15 kbar ~ 45 kbar, the mergence and/or order-reversal between levels and levels take place, which cause the fluctuation of the rate of PS for with pressure. At 300 K, both the temperature-dependent contribution to R<SUB>1</SUB> line (or R<SUB>2</SUB> line or U band) from EPI and the temperature-independent one are important.展开更多
By means of both a theory for pressure-induced shifts (PS) of energy spectra and a theory for shifts of energy spectra due to electron-phonon interaction (EPI), the 'pure electronic' PS and the PS due to EPI o...By means of both a theory for pressure-induced shifts (PS) of energy spectra and a theory for shifts of energy spectra due to electron-phonon interaction (EPI), the 'pure electronic' PS and the PS due to EPI of R<SUB>1</SUB> line of GSGG:Cr<SUP>3+</SUP> at 70 K have been calculated, respectively. Their physical origins have been revealed. It is found that the admixture of and base-wavefunctions in the wavefunctions of R<SUB>1</SUB> level of GSGG:Cr<SUP>3+</SUP> at 70 K is remarkable under the normal pressure, and the degree of the admixture rapidly decreases with increasing pressure. The change of the degree of the admixture with the pressure plays a key role for not only the pure electronic PS of R<SUB>1</SUB> line but also the PS of R<SUB>1</SUB> line due to EPI. The detailed calculations and analyses show that the pressure-dependent behaviors of the pure electronic PS of R<SUB>1</SUB> line and the PS of R<SUB>1</SUB> line due to EPI are quite different. It is the combined effect of them that gives rise to the total PS of R<SUB>1</SUB> line, which has satisfactorily explained the experimental data (including a reversal of PS of R<SUB>1</SUB> line). In contributions to PS of R<SUB>1</SUB> line due to EPI at 70 K, the temperature-independent contribution is much larger than the temperature-dependent contribution. The former results from the interaction between the zero-point vibration of the lattice and localized electronic state.展开更多
A theory for shifts of energy spectra due to electron-phonon interaction (EPI) has been developed. Both the temperature-independent contributions and the temperature-dependent ones of acoustic branches and optical bra...A theory for shifts of energy spectra due to electron-phonon interaction (EPI) has been developed. Both the temperature-independent contributions and the temperature-dependent ones of acoustic branches and optical branches have been derived. It is found that the temperature-independent contributions are very important, especially at low temperature. The total pressure-induced shift (PS) of a level (or spectral line or band) is the algebraic sum of its PS without EPI and its PS due to EPI. By means of both the theory for shifts of energy spectra due to EPI and the theory for PS of energy spectra, the total PS of R<SUB>1</SUB> line of tunable laser crystal GSGG:Cr<SUP>3+</SUP> at 70 K as well as the ones of its R<SUB>1</SUB> line, R<SUB>2</SUB> line and U band at 300 K will be successfully calculated and explained in this series of papers.展开更多
The electrical conductivity and Hall effect for T1GaSeS crystals have been investigated over a wide temperature range. The crystals we used are grown by a modified Bridgman technique and possess p-type conductivity. T...The electrical conductivity and Hall effect for T1GaSeS crystals have been investigated over a wide temperature range. The crystals we used are grown by a modified Bridgman technique and possess p-type conductivity. The energy gap has been found to be 1.63 eV, whereas the ionization energy is 0.25 eV. The variations of the Hall mobility as well as the carrier concentration with temperature have been investigated. The scattering mechanisms of the carder are checked over the whole investigated temperature range. Furthermore, the diffusion coefficient, relaxation time, and diffusion length of holes are estimated.展开更多
By means of improved ligand-field theory, the ＂pure electronic＂ pressure-induced shifts （PS＇s） and the PS＇s due to electron-phonon interaction （EPI） of R1 line and R2 line of YAG：Cr^3＋ have been calculated, ...By means of improved ligand-field theory, the ＂pure electronic＂ pressure-induced shifts （PS＇s） and the PS＇s due to electron-phonon interaction （EPI） of R1 line and R2 line of YAG：Cr^3＋ have been calculated, respectively. The calculated results are in very good agreement with the experimental data. It is demonstrated that the admixture of │t^2 2（^3T1）e^4T2〉 and │t^3 2 ^2E〉 bases in the wavefunction of RI level of YAG：Crs＋ and its change with pressure play a key role for the PS of RI line. The behaviors of the ＂pure electronic＂ PS of RI line and the PS of RI line due to EPI are different. It is the combined eEect of them that gives rise to the total PS of R1 line, which has satisfactorily explained the experimental results. The systematic analyses and comparisons between the feature of R1-line PS of YAG：Cr^3＋ and the ones of three laser crystals （GSGG：Cr^3＋, GGG：Cr^3＋ and ruby） have been made, and the origin of the difference between them has been revealed.展开更多
With the strong-field scheme and trigonal bases, the complete d<SUP>3</SUP> energy matrix in a trigonally distorted cubic-field has been constructed. By diagonalizing this matrix, the normal-pressure energ...With the strong-field scheme and trigonal bases, the complete d<SUP>3</SUP> energy matrix in a trigonally distorted cubic-field has been constructed. By diagonalizing this matrix, the normal-pressure energy spectra and wavefunctions of GSGG:Cr<SUP>3+</SUP> at 70 K and 300 K have been calculated without the electron-phonon interaction (EPI), respectively. Further, the contributions to energy spectra from EPI at two temperatures have also been calculated, where temperature-independent terms of EPI are found to be dominant. The sum of aforementioned two parts gives rise to the total energy spectrum. The calculated results are in good agreement with all the optical-spectral experimental data and the experimental results of and . It is found that the contribution from EPI to R<SUB>1</SUB> line of GSGG:Cr<SUP>3+</SUP> with taking into account spin-orbit interaction (H<SUB>so</SUB>) and trigonal field (V<SUB>trig</SUB>) is much larger than the one with neglecting H<SUB>so</SUB> and V<SUB>trig</SUB>, and accordingly it is essential for the calculation of the EPI effect to take first into account H<SUB>so</SUB> and V<SUB>trig</SUB>. The admixture of base-wavefunctions,and , the average energy separation and their variations with temperature have been calculated and discussed.展开更多
To develop a NaI （T1） detector for in situ radioactivity monitoring in the marine environment and enhance the confidence of the probability of the gamma-spectrum analysis, Monte Carlo simulations using the Monte Car...To develop a NaI （T1） detector for in situ radioactivity monitoring in the marine environment and enhance the confidence of the probability of the gamma-spectrum analysis, Monte Carlo simulations using the Monte Carlo N-Particle （ MNCP ） code were performed to provide the response spectra of some interested radionuclides and the background spectra originating from the natural radionuclides in seawater recorded by a NaI （T1） detector. A newly developed 75 mm × 75 mm NaI （T1） detector was calibrated using four reference radioactive sources 137Cs, 60Co, 40K and 54Mn in the laboratory before the field measurements in seawater. A simulation model was established for the detector immersed in seawater. The simulated spectra were all broadened with Gaussian pulses to reflect the statistical fluctuations and electrical noise in the real measurement. The simulated spectra show that the single-energy photons into the detector are mostly scattering low-energy photons and the high background in the low energy region mainly originates from the Compton effect of the high energy y-rays of natural radionuclides in seawater. The simulated background spectrum was compared with the experimental one recorded in field measurement and they seem to be in good agreement. The simulation method and spectra can be used for the accurate analysis of the filed measurement results of low concentration radioactivity in seawater.展开更多
In the last years, the production of optical fibers cables has made possible the development of a range of spectroscopic probes for in situ analysis performing beyond nondestructive tests, environmental monitoring, se...In the last years, the production of optical fibers cables has made possible the development of a range of spectroscopic probes for in situ analysis performing beyond nondestructive tests, environmental monitoring, security investigation, application in radiotherapy for dose monitoring, verification and validation. In this work, a system using an optical fiber cable to electromagnetic signal transmission from a NaI（TI） radiation detector is presented. The innovative device takes advantage mainly of the optical fibers large passband, small signal attenuation and immunity to electromagnetic interference to application for radiation detection systems. The main aim was to simplify the detection system making it to reach areas where the conventional device cannot access due to its lack of mobility and external dimensions. Some tests with this innovative system are presented and the results stimulate the continuity of the researches.展开更多
文摘By means of both a theory for pressure-induced shifts (PS) of energy spectra and a theory for shifts of energy spectra due to electron-phonon interaction (EPI), the 'pure electronic' PS and the PS due to EPI of R<SUB>1</SUB> line, R<SUB>2</SUB> line, and U band of GSGG:Cr<SUP>3+</SUP> at 300 K have been calculated, respectively. The calculated results are in good agreement with all the experimental data. Their physical origins have also been explained. It is found that the mixing-degree of and base-wavefunctions in the wavefunctions of R<SUB>1</SUB> level of GSGG:Cr<SUP>3+</SUP> at 300 K is remarkable under normal pressure, and the mixing-degree rapidly decreases with increasing pressure. The change of the mixing-degree with pressure plays a key role not only for the 'pure electronic' PS of R<SUB>1</SUB> line and R<SUB>2</SUB> line but also the PS of R<SUB>1</SUB> line and R<SUB>2</SUB> line due to EPI. The pressure-dependent behaviors of the 'pure electronic' PS of R<SUB>1</SUB> line (or R<SUB>2</SUB> line) and the PS of R<SUB>1</SUB> line (or R<SUB>2</SUB> line) due to EPI are quite different. It is the combined effect of them that gives rise to the total PS of R<SUB>1</SUB> line (or R<SUB>2</SUB> line). In the range of about 15 kbar ~ 45 kbar, the mergence and/or order-reversal between levels and levels take place, which cause the fluctuation of the rate of PS for with pressure. At 300 K, both the temperature-dependent contribution to R<SUB>1</SUB> line (or R<SUB>2</SUB> line or U band) from EPI and the temperature-independent one are important.
文摘By means of both a theory for pressure-induced shifts (PS) of energy spectra and a theory for shifts of energy spectra due to electron-phonon interaction (EPI), the 'pure electronic' PS and the PS due to EPI of R<SUB>1</SUB> line of GSGG:Cr<SUP>3+</SUP> at 70 K have been calculated, respectively. Their physical origins have been revealed. It is found that the admixture of and base-wavefunctions in the wavefunctions of R<SUB>1</SUB> level of GSGG:Cr<SUP>3+</SUP> at 70 K is remarkable under the normal pressure, and the degree of the admixture rapidly decreases with increasing pressure. The change of the degree of the admixture with the pressure plays a key role for not only the pure electronic PS of R<SUB>1</SUB> line but also the PS of R<SUB>1</SUB> line due to EPI. The detailed calculations and analyses show that the pressure-dependent behaviors of the pure electronic PS of R<SUB>1</SUB> line and the PS of R<SUB>1</SUB> line due to EPI are quite different. It is the combined effect of them that gives rise to the total PS of R<SUB>1</SUB> line, which has satisfactorily explained the experimental data (including a reversal of PS of R<SUB>1</SUB> line). In contributions to PS of R<SUB>1</SUB> line due to EPI at 70 K, the temperature-independent contribution is much larger than the temperature-dependent contribution. The former results from the interaction between the zero-point vibration of the lattice and localized electronic state.
文摘A theory for shifts of energy spectra due to electron-phonon interaction (EPI) has been developed. Both the temperature-independent contributions and the temperature-dependent ones of acoustic branches and optical branches have been derived. It is found that the temperature-independent contributions are very important, especially at low temperature. The total pressure-induced shift (PS) of a level (or spectral line or band) is the algebraic sum of its PS without EPI and its PS due to EPI. By means of both the theory for shifts of energy spectra due to EPI and the theory for PS of energy spectra, the total PS of R<SUB>1</SUB> line of tunable laser crystal GSGG:Cr<SUP>3+</SUP> at 70 K as well as the ones of its R<SUB>1</SUB> line, R<SUB>2</SUB> line and U band at 300 K will be successfully calculated and explained in this series of papers.
文摘The electrical conductivity and Hall effect for T1GaSeS crystals have been investigated over a wide temperature range. The crystals we used are grown by a modified Bridgman technique and possess p-type conductivity. The energy gap has been found to be 1.63 eV, whereas the ionization energy is 0.25 eV. The variations of the Hall mobility as well as the carrier concentration with temperature have been investigated. The scattering mechanisms of the carder are checked over the whole investigated temperature range. Furthermore, the diffusion coefficient, relaxation time, and diffusion length of holes are estimated.
文摘By means of improved ligand-field theory, the ＂pure electronic＂ pressure-induced shifts （PS＇s） and the PS＇s due to electron-phonon interaction （EPI） of R1 line and R2 line of YAG：Cr^3＋ have been calculated, respectively. The calculated results are in very good agreement with the experimental data. It is demonstrated that the admixture of │t^2 2（^3T1）e^4T2〉 and │t^3 2 ^2E〉 bases in the wavefunction of RI level of YAG：Crs＋ and its change with pressure play a key role for the PS of RI line. The behaviors of the ＂pure electronic＂ PS of RI line and the PS of RI line due to EPI are different. It is the combined eEect of them that gives rise to the total PS of R1 line, which has satisfactorily explained the experimental results. The systematic analyses and comparisons between the feature of R1-line PS of YAG：Cr^3＋ and the ones of three laser crystals （GSGG：Cr^3＋, GGG：Cr^3＋ and ruby） have been made, and the origin of the difference between them has been revealed.
文摘With the strong-field scheme and trigonal bases, the complete d<SUP>3</SUP> energy matrix in a trigonally distorted cubic-field has been constructed. By diagonalizing this matrix, the normal-pressure energy spectra and wavefunctions of GSGG:Cr<SUP>3+</SUP> at 70 K and 300 K have been calculated without the electron-phonon interaction (EPI), respectively. Further, the contributions to energy spectra from EPI at two temperatures have also been calculated, where temperature-independent terms of EPI are found to be dominant. The sum of aforementioned two parts gives rise to the total energy spectrum. The calculated results are in good agreement with all the optical-spectral experimental data and the experimental results of and . It is found that the contribution from EPI to R<SUB>1</SUB> line of GSGG:Cr<SUP>3+</SUP> with taking into account spin-orbit interaction (H<SUB>so</SUB>) and trigonal field (V<SUB>trig</SUB>) is much larger than the one with neglecting H<SUB>so</SUB> and V<SUB>trig</SUB>, and accordingly it is essential for the calculation of the EPI effect to take first into account H<SUB>so</SUB> and V<SUB>trig</SUB>. The admixture of base-wavefunctions,and , the average energy separation and their variations with temperature have been calculated and discussed.
基金financial support from the International Science & Technology Cooperation Program of China (No. 2013DFR90220)National Natural Science Foundation of China (No. 41206076)Qingdao Applied Basic Research Project (NO. 14-2-4-94-jch)
文摘To develop a NaI （T1） detector for in situ radioactivity monitoring in the marine environment and enhance the confidence of the probability of the gamma-spectrum analysis, Monte Carlo simulations using the Monte Carlo N-Particle （ MNCP ） code were performed to provide the response spectra of some interested radionuclides and the background spectra originating from the natural radionuclides in seawater recorded by a NaI （T1） detector. A newly developed 75 mm × 75 mm NaI （T1） detector was calibrated using four reference radioactive sources 137Cs, 60Co, 40K and 54Mn in the laboratory before the field measurements in seawater. A simulation model was established for the detector immersed in seawater. The simulated spectra were all broadened with Gaussian pulses to reflect the statistical fluctuations and electrical noise in the real measurement. The simulated spectra show that the single-energy photons into the detector are mostly scattering low-energy photons and the high background in the low energy region mainly originates from the Compton effect of the high energy y-rays of natural radionuclides in seawater. The simulated background spectrum was compared with the experimental one recorded in field measurement and they seem to be in good agreement. The simulation method and spectra can be used for the accurate analysis of the filed measurement results of low concentration radioactivity in seawater.
文摘In the last years, the production of optical fibers cables has made possible the development of a range of spectroscopic probes for in situ analysis performing beyond nondestructive tests, environmental monitoring, security investigation, application in radiotherapy for dose monitoring, verification and validation. In this work, a system using an optical fiber cable to electromagnetic signal transmission from a NaI（TI） radiation detector is presented. The innovative device takes advantage mainly of the optical fibers large passband, small signal attenuation and immunity to electromagnetic interference to application for radiation detection systems. The main aim was to simplify the detection system making it to reach areas where the conventional device cannot access due to its lack of mobility and external dimensions. Some tests with this innovative system are presented and the results stimulate the continuity of the researches.
