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1.
The microwave absorption dielectric spectrum can be used to study the decay process of free photoelectrons and shallow-trapped electrons in semiconductor crystals. The decay curve of free photoelectrons and shallow-trapped electrons of silver halide grains is measured using this technique. The influence of iodide and K_4Fe(CN)_6 shallow electron trap dopants on the photoelectron lifetime of silver halide grains is studied. For the unsensitized cubic AgCl crystals, when the free photoelectron lifetime (FLT) reaches a maximum, the photographic efficiency is optimal. From our analysis, we conclude that FLT is the longest for the cubic AgCl crystals doped with 0.5% iodide at 80% doping position and 1×10^{-6} mol K_4Fe(CN)_6/molAg, whereas, for the highly photosensitized cubic AgBrCl crystals doped with K_4Fe(CN)_6, the photographic efficiency is optimal when the FLT reaches its minimum. The free photoelectron lifetime reaches minimum and the sensitivity of AgBrCl emulsion reaches maximum when the doping position is 30%Ag at K_4Fe(CN)_6 content of 10^{-6}mol/molAg. 相似文献
2.
The influence of trapping centres on the photoelectron decay in silver halide 总被引:3,自引:0,他引:3 下载免费PDF全文
Photoelectron is the foundation of latent image formation, the decay process of photoelectrons is influenced by all kinds of trapping centres in silver halide. By analysing the mechanism of latent image formation it is found that electron trap, hole trap, and one kind of recombination centre where free electron and trapped hole recombine are the main trapping centres in silver halide. Different trapping centres have different influences on the photoelectron behaviour. The effects of all kinds of typical trapping centres on the decay of photoelectrons are systematically investigated by solving the photoelectron decay kinetic equations. The results are in agreement with those obtained in the microwave absorption dielectric spectrum experiment. 相似文献
3.
The microwave absorption dielectric-spectrum technique was used to study the decay kinetics of photoelectrons in sulfur-sensitized
silver halide crystals. The time-resolution spectrum of free electrons and shallow-trapped electrons generated in sulfur-sensitized
AgBrl crystals has been obtained. The relationship of the trapping effect of sensitization centers Ag2S and sensitization time or temperature in emulsions has been duscussed. With the increase in the sensitization time and temperature,
the trap effect of sulfur sensitization centers varies from hole trap to shallow electron trap, and deep electron trap. 相似文献
4.
YANG Shaopeng FU Guangsheng LI Xiaowei & TIAN Xiaodong College of Physics Science Technology Hebei University Baoding China 《中国科学G辑(英文版)》2004,47(6)
Chemical sensitization is a widely adopted technique that improves the photo-graphic sensitivity of silver halide crystals with basic emulsion. Sensitization centers,which can save photoelectrons in the process of latent-image formation, have beenformed on microcrystals after chemical sensitization. Therefore, chemical sensitizationwas widely adopted for many years. Sulfur sensitization is an important chemical sen-sitization technique in all chemical sensitization methods. First, in 1925, Sh… 相似文献
5.
甲酸根离子(HCO-2)作为一种“空穴-电子转换剂”掺杂在卤化银中,可以提高潜影形成过程中光电子的利用率,俘获光生空穴,减少潜影形成过程中电子-空穴复合所造成的电子损失;同时还可以释放一个电子,提高感光效率。采用微波吸收介电谱检测技术,检测了不同浓度甲酸根离子均匀掺杂的立方体AgCl和AgBr乳剂在脉冲激光作用下所产生的光电子衰减信号。通过比较光电子的衰减时间和寿命,分析了甲酸根离子的空穴陷阱效应对立方体AgCl和AgBr乳剂中光电子衰减行为的影响,并得到了最佳均匀掺杂浓度(10-5mol/molAg)。 相似文献
6.
Kinetics study of ultrafast electron transfer from sensitized dyes to silver halide microcrystals 总被引:1,自引:0,他引:1 下载免费PDF全文
Spectral sensitization micromechanism of cyanine dyes J-aggregate adsorbed
on the tabular and cubic AgBr microcrystals with different dye
concentrations
is studied by using picosecond time-resolved fluorescence spectroscopy, and
the dependences of electron transfer and spectral efficiency sensitization
on different conditions are analysed in detail. With the steady
spectroscopy, the wavelengths of absorption and fluorescence of J-aggregate
adsorbed on AgBr microcrystals are found to shift to red relative to dye
monomer. The spectrum of fluorescence has a red shift relative to the
absorption peak. With the time-resolved fluorescence spectroscopy, the
fluorescence decay curves of cyanine dyes J-aggregate adsorbed on the
tabular and cubic AgBr grains are found to be fitted well by a
double-exponential decay function. The fitting curves consist of a fast and
a slow component. Because of the large amplitude of the fast component, this
fast decay should be attributable mainly to the electron transfer from
J-aggregate of dye to a conduction band of AgBr. 相似文献
7.
This theoretical study summarizes ionic and electronic processes in AgBr crystals and the influence of its results on photographic
process. It deals with the importance of surface generated interstitials which Gurney and Mott left untouched because of the
non-availability of sufficient data at that time. The magnitude of various parameters,e.g., mean intra-electron-ion distance in a latent image site, the rate of neutralization of Ag+ ion with trapped electron and capture cross-section for combination of Ag+ ion with the trapped electron, etc. (as desired for understanding the theory of photographic process) are calculated at different
temperatures. The results when used in our earlier papers (Singh and Sharma, 1974 and 1975, and Singh 1975) for calculating
charged particle track characteristics theoretically were found to give good agreement with the published experimental data
(Della Corteet al 1953 and Dyer and Hechman 1967). A model for the mechanism of latent image formation (silver speck) is discussed. 相似文献
8.
9.
A comment on the number of sensitivity centres in silver halide grains of nuclear emulsions is made and a theory for its evaluation
at different temperatures is presented. The results at room temperature agree satisfactorily with assumptions made by various
workers. 相似文献
10.
The fractional ionic character of alkali and silver halide crystals is defined in terms of the deviations from the additivity
rule for polarizabilities of ions. The electronic polarizabilities of ions are calculated using an empirical relationship
according to which the electronic polarizability of an ion can be assumed to be directly proportional to the cube of its radius.
The calculated ionicities indicate that the alkali halides are nearly or more than 90% ionic and silver halides are much less
ionic which is also evident from the Phillips ionicity scale. 相似文献
11.
Wook Jae Yoo Dong Hyun Cho Kyoung Won Jang Sang Hun Shin Jeong Ki Seo Soon-Cheol Chung Bongsoo Lee Byung Gi Park Joo Hyun Moon Young-Ho Cho Sin Kim 《Optical Review》2009,16(3):387-391
In this study, we have fabricated non-contact temperature sensor using an infrared optical fiber for measuring temperature
distributions during radiofrequency ablation. We have measured an infrared radiation, which is transferred by a silver halide
optical fiber from the multi-points on the water around inserted electrode, using a thermopile sensor and the output voltages
of a thermopile sensor are compared with those of the thermocouple recorder. Also, the relationship between the temperatures
and the output voltages of a thermopile sensor at the measuring points is determined to obtain the temperature distribution.
The measurable temperature range of a fiber-optic non-contact temperature sensor is from 37 to 80 °C. 相似文献
12.
13.
In recent years, the formate ion (HCO2^-) as a kind of hole-to-electron converter has attracted much attention of photographic researchers. The formate ions can trap photo-generated holes, eliminate or reduce the electron loss caused by electron-hole recombination in latent image formation process. Through the hole-to-electron conversion, it can also release an extra electron or electron carrier, improving photosensitivity. In this paper the microwave absorption and dielectric spectrum detection technique is used to detect the time evolution behaviour of free photoelectrons generated by 35ps laser pulses in cubic AgCl emulsions doped with formate ions. The influence of different doping conditions of formate ions on the photoelectron decay kinetics of AgC1 is analysed. It is found that when the HCO2^- content is 10^-3mol/mol Ag and the doping position is 90% the electron decay time and lifetime reach their maxima due to the efficient trap of holes by formate ions. 相似文献
14.
Ferromagnetic resonance (FMR), Ferromagnetic antirresonance (FMAR) and low field magnetoimpedance (MI) are the characteristic features of high frequency losses in applied fields. While some results on FMR and FMAR in CoFeNi electroplated wires were reported earlier, here we present microwave absorption in CuBe wires electroplated by 1 μm FeCoNi magnetic layer at very low fields. These data are comparatively analysed together with longitudinal hysteresis loops in order to reveal the correlation between power absorption and magnetization processes. Microwave studies are made by using the cavity perturbation method at 9.65 GHz for a DC field parallel to the sample axis, and with microwave magnetic field hrf parallel or perpendicular to the wire axis. Two peaks have been observed in all samples, one is due to FMR, and the other is, at very low fields, related to MI. The MI peaks represent minima in power absorption. By comparing with the hysteresis loop we remark the close correspondence between the MI phenomena in the axial mode and the concomitant magnetization process. 相似文献
15.
Templated synthesis of highly ordered mesoporous cobalt ferrite and its microwave absorption properties 下载免费PDF全文
Based on the nanocasting strategy, highly ordered mesoporous CoFe2O4 is synthesized via the ‘two-solvent’ impregnation method using a mesoporous SBA-15 template. An ordered two-dimensional(P6mm) structure is preserved for the CoFe2O4/SBA-15 composite after the nanocasting. After the SBA-15 template is dissolved by NaOH solution, a mesoporous structure composed of aligned nanoparticles can be obtained, and the P6 mm structure of the parent SBA-15is preserved. With a high specific surface area(above 90 m2/g) and ferromagnetic behavior, the obtained material shows potential in light weight microwave absorption application. The minimum reflection loss(RL) can reach-18 dB at about16 GHz with a thickness of 2 mm and the corresponding absorption bandwidth is 4.5 GHz. 相似文献
16.
H. GaviB.D. Ngom A.C. BeyeA.M. Strydom V.V. Srinivasu M. ChakerN. Manyala 《Journal of magnetism and magnetic materials》2012,324(6):1172-1176
Low field microwave absorption (LFMA) measurements at 9.4 GHz (X-band), were carried out on pulse laser deposited (PLD) polycrystalline B20 cubic structure FeSi thin film grown on Si (111) substrate. The LFMA properties of the films were investigated as a function of DC field, temperature, microwave power and the orientation of DC field with respect to the film surface. The LFMA signal is very strong when the DC field is parallel to the film surface and vanishes at higher angles. The LFMA signal strength increases as the microwave power is increased. The LFMA signal disappears around 340 K, which can be attributed to the disappearance of ferromagnetic state well above room temperature in these films. We believe that domain structure evolution in low fields, which in turn modifies the low field permeability as well as the anisotropy, could be the origin of the LFMA observed in these films. The observation of LFMA opens the possibility of the FeSi films to be used as low magnetic field sensors in the microwave and rf frequency regions. 相似文献
17.
Thermal lensing effect was studied in aqueous solutions of rhodamine B using 532 nm, 9 ns pulses from a Nd:YAG laser. A low
intensity He-Ne laser beam was used for probing the thermal lens. Results obtained show that it is appropriate to use this
technique for studying nonlinear absorption processes like two photon absorption or excited state absorption and for analyzing
dimerization equilibria. 相似文献
18.
The electric field dependence of the complex dielectric constant in an anharmonic defect ferroelectric crystal is calculated
in its paraelectric phase from the Silverman-Joseph-Hamiltonian augmented with fourth-order phonon coordinates using double-time
Green’s functions. The field and impurity dependence of the shift in the Curie temperature is discussed. An expression is
obtained for the electric field dependence of dielectric loss at microwave frequencies in defect ferroelectrics.
An erratum to this article is available at . 相似文献
19.