首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
We derive analytical expressions for Stark quantum beat signals of polyatomic molecules and discuss them with regard to molecular and geometrical parameters. The general treatment is specified for near prolate asymmetric rotor molecules and a method for determining rotational constants and all components of the dipole moment of electronically excited polyatomic molecules is presented. The method is tested and illustrated for the vibrationlessS 1 state of deuterated propynal (HC ≡ CCDO,C s symmetry) and its lowest frequency non-totally symmetric state 121. The results of the vibrationless state are compared with structural data reported in the literature. For the 121 state we obtainA=1.5004(43) cm?1,B=0.16131(34) cm?1,C=0.14623(34) cm?1, and the components of the electric dipole moment in the molecular plane μ a =?0.88(2)D, μ b =1.03(2)D. Furthermore, it is shown that the modulation depth of Stark quantum beat signals can be utilized to quantify the contribution of the individual components of the transition moment to the total emission.  相似文献   

2.
In a CW laser-atomic beam experiment Stark manifolds in barium originating from the Rydberg states 6s40f 1 F 3, 6s40g 1,3 G 4,3 G 5 and 6s40h 1,3 H 5 have been studied. Accurate quantum defect values for higher orbital angular momentum states (l=6, 7) have been determined. The Stark manifolds are also calculated by diagonalization of the energy matrix in the presence of an external electric field. Good agreement between experiment and calculations is obtained.  相似文献   

3.
The rate of quenching of triplet excitions by trapped holes in crystalline pyrene has been measured as a function of hole concentration. The rate constant is γ=4.5×10?11 cm3 sec?1 within 50%, not far below that of a diffusion limited process. The quenching by free holes is not observed in the experimental conditions used.  相似文献   

4.
Classical molecular dynamics simulations are performed to cover Stark mixing transitions (nn) in Rydberg atoms by collision with slow ions. Accuracy is tested by comparison with the exact analytical classical probabilities previously obtained when the ion–atom potential is taken as the long-range ion–dipole interaction. The results are provided not only for the ion–dipole interaction but also for the full electrostatic interaction. It is shown, by comparison, that the ion–dipole potential alone provides reliable probabilities. The method is highly accurate and is very amenable to ready inclusion of other processes competing with Stark mixing.  相似文献   

5.
The hyperfine and Stark spectrum of the J = 1←0 rotational transition of D79Br and D81Br at 254 CHz has been investigated with a high resolution millimeter-wave beam-spectrometer. The hyperfine coupling constants and the dipole moment of D79Br and D81Br have been determined. A discussion is given on the values of the field gradient and the dipole moment at the equilibrium intermuclear distance of the hydrogen bromide molecule.  相似文献   

6.
The theories of the dilatation, rr e, and translation, xx + iq, transformations as related to the Stark problem are reviewed, and new results obtained. Results for the hydrogen atom n = 1 and n = 2 levels and the 1P0, 2s2p H? shape resonance in dc fields are presented, and the extension to the ac Stark effect made. Spectral estimates are made using the technique of the numerical range and via discussion of several model problems, using both coordinate rotation and coordinate translation.  相似文献   

7.
The Stark full widths at half of the maximal line intensity (FWHM, ω) have been measured for 25 spectral lines of Pb III (15 measured for the first time) arising from the 5d106s8s, 5d106s7p, 5d106s5f and 5d106s5g electronic configurations, in a lead plasma produced by ablation with a Nd:YAG laser. The optical emission spectroscopy from a laser-induced plasma generated by a 10 640 Å radiation, with an irradiance of 2 × 1010 W cm− 2 on a lead target (99.99% purity) in an atmosphere of argon was analysed in the wavelength interval between 2000 and 7000 Å. The broadening parameters were obtained with the target placed in argon atmosphere at 6 Torr and 400 ns after each laser light pulse, which provides appropriate measurement conditions. A Boltzmann plot was used to obtain the plasma temperature (21,400 K) and published values of the Stark widths in Pb I, Pb II and Pb III to obtain the electron number density (7 × 1016 cm− 3); with these values, the plasma composition was determined by means of the Saha equation. Local Thermodynamic Equilibrium (LTE) conditions and plasma homogeneity has been checked. Special attention was dedicated to the possible self-absorption of the different transitions. Comparison of the new results with recent available data is also presented.  相似文献   

8.
Stark widths and shifts of sixCII, threeCIII and twoCIV spectral lines have been measured in a linear pinch discharge plasma and compared with available experimental and theoretical data. Electron density, (0.86?1.64)×1023 m?3, was determined by single wavelength laser interferometry using the visible 632.8 nm transition of He-Ne laser. The electron temperature of 38000 K was derived from the Boltzmann slope of severalCII spectral lines, and ratios of severalCII toCIII spectral lines. The stark widths (w) dependence on:(i) the upper-level ionization potential (I) of corresponding lines;(ii) net charge (z) of the emitter core seen by the optical electron undergoing transition, and(iii) electron temperature (T) was found to be of the form:w=az 2 T ?1/2 I ?b . However, it should be noticed that the essential role in the obtained trends belongs to the energy of the emitter core. The established overall trend is used to predict Stark widths of uninvestigated spectral lines originating from the given transition arrays.  相似文献   

9.
A direct experimental comparison is performed for the field dependences of drift and effective mobilities of holes in a polar molecularly doped polymer (polycarbonate containing 30 wt % p-diethylaminobenzaldehyde diphenylhydrazone), which are measured by the time-of-flight method during the bulk irradiation of polymer samples with a pulse of fast electrons. A numerical simulation of the time-of-flight experiments is conducted with the use of the multiple-trapping model with the Gaussian energy trap distribution. The parameters of the model are determined during independent measurements. It is shown that, because of the nonequilibrium state of the transport of holes under the conditions of the time-of-flight experiment, the true Poole–Frenkel constant (0.27 (μm/V)1/2) makes up only a part of the experimentally measured value (0.39 (μm/V)1/2).  相似文献   

10.
The specific features of charge carrier transport in poly(N-vinylcarbazole) films doped with single-wall carbon nanotubes have been investigated. The mobilities of electrons and holes in ITO-polymer composite-Al samples have been determined by the time-of-flight method and by measuring the voltage-current characteristics of steady-state currents. According to the time-of-flight experiments, in the films of a poly(N-vinylcarbazole)-0.26 wt % single-wall carbon nanotubes composite, the drift mobility of electrons lies within (1.2–4.5) × 10?6 cm2/(V s) and exceeds the mobility of holes by a factor of 5. The shape of the transient current suggests the dispersion character of transport of electrons and holes. With an increase in the concentration of single-wall nanotubes from 0.26 to 0.43 wt %, the conductivity of the composite films increases by two orders of magnitude; that is, the threshold of conductivity percolation has been achieved. A simple model is proposed to describe the transport of charge carriers in the polymer system under study.  相似文献   

11.
In this work, we have studied the main conditions that a laser-induced plasma must fulfill in order to be considered as adequate for the measurement of Stark broadening parameters. We investigated the effect of the temporal window, the self-absorption, the crater size, and the effect of the spatial inhomogeneity on the emission profiles coming from a laser-induced plasma. Starting from the spatially resolved values of the plasma parameters, obtained by emission spectroscopy, the error in the determination of the Stark electron width due to the spatial inhomogeneity has been estimated and, for the present experimental conditions, was found to be lower than 7%. As a test of the method, the Stark electron broadening constant of Fe I 381.58 nm has been measured using the Fe I 538.34 nm emission line as the reference to determine the electron density. The plasma was produced under a controlled atmosphere of argon at atmospheric pressure, on an iron–nickel alloy sample. The emission was collected by a system with high spectral resolution, for different temporal windows after the laser pulse. For time delays between 2.75 and 21 μs, the electron density showed an evolution in the range 2.0–0.13 × 1017 cm 3, while the temperature varied from 11 100 to 7100 K. The representation of the Stark electron width of Fe I 381.58 nm, measured for each temporal window, versus the Stark electron width of the reference line showed a linear behavior with a high correlation coefficient. From the slope of this linear fit and the Stark electron broadening constant of the reference line, the Stark width of Fe I 381.58 nm was obtained to be 1.10 ± 0.07 × 10 2 nm for an electron density of 1017 cm 3.  相似文献   

12.
The decay kinetics of electrons generated in thin CdSe films by laser pulse (wavelength 337 nm, pulse duration 8 ns) at 295 K was studied by the microwave photoconductivity method (36 GHz). Based on analysis of the photoresponse decay kinetics and the reactions of free and trapped electrons, holes, and ions, a model for the processes was proposed and the recombination rate constant of free electrons and holes in cadmium selenide was determined, being (4–6)· 10–11 cm3 s−1. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 740–743, May, 2006. The samples were kindly presented by Yu. V. Meteleva.  相似文献   

13.
The shapes of 16 doubly ionized indium (In III) spectral lines have been measured in the laboratory helium plasma at 13,000 K electron temperature and 1.48 × 1023 m 3 electron density. At mentioned plasma conditions the Stark broadening has been found as the dominant mechanism in the line shape formation. Here presented data are the first reported values for Stark widths (W) related to the specific In III lines. The modified version of the linear, low-pressure, pulsed arc was used as a plasma source operated in helium with indium atoms, as impurities, evaporated from indium cylindrical plates located in the homogenous part of the discharge, providing conditions free of self-absorption. At the above mentioned helium plasma conditions we have found symmetrical In III line profiles of the Voigt type. This means that the expected hyperfine structure splitting (Δhfs) in the investigated In III lines has been overpowered by Stark and Doppler broadening. We recommend the found W values of the intense and well isolated 298.280, 403.232 and 524.877 nm In III lines for the plasma electron density diagnostic ranged between 1021 m 3 and 1023 m 3.  相似文献   

14.
The half-width and asymmetry parameter of the He I 21 P–31 D λ=667.8 nm line have been measured in a laser produced He plasma for electron densitiesN e between 7×1022 m?3 and 1.7×1023 m?3. Results, obtained for the half-width, agree very well with the theoretical results forN e ?1023 m?3 and the agreement becomes somewhat worse forN e >1023 m?3. We have measured the red asymmetry which is considerable lower than the theoretical one. We have also established good agreement with theoreticalj A,R (x) profile for this line.  相似文献   

15.
The solvent Stark effect on the spectral shifts of anthracene is studied with temperature-dependent solvatochromic measurements. The Stark contribution ΔvStark to the absorption shift Δvp in polar solvents is measured to be ΔvStark=(53±35) cm−1, in reasonable agreement with dielectric continuum theory estimate of 28 cm−1, whereas the major shift Δvp∼300 cm−1 presumably originates from the solute quadrupole. We pay attention to the accurate correction of Δvp for the nonpolar contribution that is crucial when the shifts are modest in magnitude.  相似文献   

16.
Electrical conductivity, thermopower and oxygen content were measured for La1−xSrxFeO3−δ (x=0.2, 0.5, 0.9) within the oxygen partial pressure range 10−4-0.5 atm and at temperatures 750-950 °C. The dominating charge carriers under these experimental conditions are electron holes. The results of oxygen nonstoichiometry measurements are used to estimate the concentration of holes and to analyze data on conductivity and thermopower. The changes in thermopower are described by the model assuming that the number of sites accessible for migration of holes is independent on oxygen content. The mobility of electron holes is calculated, and it is found to be virtually independent on temperature in the compositions with x<0.5 while compositions with x>0.5 exhibit thermally activated mobility and mobility values about 0.1 cm2 V−1 s−1 or smaller. It is suggested that the main contribution to the composition dependent variations in electron hole mobility are associated with Coulomb interactions at small x's, whereas at high degrees of doping the mobility of holes is most strongly affected by the increasing amount of oxygen vacancies.  相似文献   

17.
The transient kinetics of the loss of electrons generated by light pulses in powdered AgCl has been studied by the microwave photoconductivity method (36 GHz) at 295 K. At high light intensities,I 0 > 1014 photon cm–2 per pulse, the kinetics obeys the second-order law. The rate constant of the recombination of free electrons and holes is equal to 2·10–12 cm3 s–1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2234–2236, September, 1996.  相似文献   

18.
The Stark effect on the visible absorption spectra of p-benzoquinone single crystals has been measured using modulation techniques. The measurements of second order Stark effects confirm the presence of at least two close lying electronic nπ* states in both the singlet and triplet systems. Both the origin of the first singlet-singlet and singlet—triplet transition appear as doublets separated by 3.5 and 18 cm?1, respectively. For the triplet state the low energy component is Stark induced and has not been observed previously in absorption. The doublet components are mixed in the electric field showing that they are of different parity. They are tentatively assigned as inversion doublets of a symmetric double well potential produced by the vibronic interaction of two different electronic nπ* states.  相似文献   

19.
Isotopic exchange of α and ß-cobalt phthalocyanine (CoPc) doped with carrier-free 57CoCl2 was studied at different temperatures in presence, and absence of oxygen. In samples sealed in evacuated vials, the exchange is induced by electrons released from multi-depth donors. The results show that ß-CoPc has a smaller density of donors and a deeper distribution in depths, as compared to α-CoPc. The mode of population of traps with electrons (or holes) during the preparation is discussed.Thermal treatment of CoPc in air and followed by doping with 57CoCl2 (and radiochemical analysis) gives us the magnitude of isotopic exchange induced by holes, which are injected by virtue of charge transfer interactions between molecules of CoPc and O2. Our observations indicate that the rate of diffusion of O2 into CoPc crystallites depends on the temperature and the period of thermal treatment. The diffusion continues well beyond 1 week even at relatively high temperatures. The concentration of the injected holes and therefore the magnitude of exchange depends on the size of particles. The diffusion and chemisorption of O2 seems to be facilitated considerably when the microcrystallites of CoPc are suspended in oxygenated water (as compared to the dry powder).When aliquots of 57Co2+-doped CoPc are compacted with o-chloranil or iodine, strong charge transfer interactions between CoPc, and o-chloranil, and (to a lesser extent) iodine molecules, inject high concentrations of holes and thereby induce considerable exchange.When samples of 57Co2+-doped α- or ß-CoPc are heated in air, either detrapped electrons or injected holes may induce exchange. In ball-milled samples, consisting of very fine particles, the contributions towards exchange by electrons and holes, become additive. This amazing observation indicates that large non-equilibrium concentrations of electrons and holes co-exist for considerable lengths of time without recombination.In conclusion, the dopant 57Co2+ in CoPc constitutes a good probe and we have obtained a wealth of information which would be difficult to obtain by purely physical measurements.  相似文献   

20.
In the electric field and layer-to-layer interaction energy, the law of split-level of high-level Stark effect of spherical nanometer system is explored as well as the frequency of spectrum,intensity and size effect of coefficient of spontaneous radiation. Taking three layers CdS/HgS spherical nanometer system as an example, the influence of the electric field and layer-to-layer interaction energy is explored on Stark effect and spectrum. The results show that in the Stark effect system, the energy level is split based on 1, 3,… , (2n—1), when it is in the electric field only, similar to the hydrogen atoms; and in the electric field and layer-to-layer interaction, it is split based on 1, 4, … , n2; with the quantum transition, the frequency of the spectrum decreases with the increasing size of the system; apart from a few spectral lines, the intensity of most spectral lines will decreased as the size increases; while the coefficient of spontaneous radiation will increase with the increasing size; the electric field will causethe changes of spectrum frequency; its spectrum frequency shift is proportional to the square of the electric field intensity; apart from a few spectral lines, the frequency shift of spectral lines that is caused by the electric field and layer-to-layer interaction will decrease as the size increases; the interaction will make the level of electronic energy level lower slightly (the order of magnitude is between 10-7—10-9 eV), the slightly increased spectrum intensity and the slightly increased value of coefficient of spontaneous radiation, but it will not influence the frequency of spectrum, intensity, and the trend that coefficient of spontaneous radiation changes with the size; when the size is smaller, the layer-to-layer interaction effect will be significant.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号