Jin Sizhao

Preparation and electron spin resonance effect of nanometer-sized Mn2O3

Abstract Nanometer-sized manganic oxide (Mn 2 O 3 ) has been prepared for the first time by a chemical liquid homogeneous precipitation (CLHP) method. Transmission electron micrographs and X-ray powder diffraction patterns show that the average particle sizes are in the range of 9–50 nm. From the electron spin resonance (ESR) patterns of 9 nm manganic oxide particle, we can observe hyperfine structure (Six absorption peaks of ESR) of Mn 2+ ion adding the Mn 3+ ion signal.

ESR dating of tooth enamel: comparison with U-series, FT and TL dating at the Peking Man site

Deer tooth samples from Zhoukoudian, the Peking Man Cave, were studied. Non-linear fitting is used to determine AD, from which ESR ages were calculated by both the disequilibria model (DU) and linear uptake model (LU). Comparison of ESR ages with those from U-series, FT and TL methods show that the enamel of deer teeth is a suitable material for ESR dating.

Estimation of the influence of experimental conditions on ESR dating results

Abstract Rapid progress has recently been made in ESR dating, a new dating technique. Much attention has been paid to the accuracy of its results, as errors may be caused by various factors. This paper probes into the influence of the applied microwave power and the absorbed dose rate of additional radiation. A few measurements we made with carbonate and quartz samples reveal that the microwave power saturation point depends on the type of paramagnetic centers and the type of samples. The microwave power and the dose rate of additional radiation have an apparent effect on the total radiation dose assessment in such samples. Extrapolating on a logarithmic scale, we determine that the ESR age of coral sample 87-04 is (3.64 ± 0.55) ka as microwave power is zero. This is in accord with its 14 C age (3.75 ± 0.19) ka.

ESR dating and trapped electrons lifetime of quartz grains in loess of China

Abstract This paper reports the preliminary application of ESR dating to loess strata. The samples were collected from the 7th palaeosol layer (S7) of the Luochuan section, Shaanxi province in China. The ESR age of S7 is 736 ka (total dose 2945 Gy, annual dose 4 mGy/year). This age represents the original eolian accumulation age. The result is consistent with the palaeomagnetic data (730 ka). We have also carried out thermal annealing experiments on quartz grains from the S7 sample. ESR intensities (g = 2.0005) increase from 25°C to 320°C. It may be that trapped electrons transfer into the E′ centre site. ESR intensities decrease from 340°C to 460°C due to thermal annealing. We obtained a mean-life of E′ centre electrons at 20°C of 6.66 × 108 years. The activation energy is 1.35 eV and frequency factor is 3.7 × 108 min−1.

A comparative study on optical effects of E′ center in quartz grains from loess and fault

Abstract This paper reports several light exposure experiments of quartz grains from loess and fault. We found that the ionizing radiation-induced E′ centers ESR signal intensities of the samples collected from either loess or fault could not be erased by exposure to sunlight and other artificial light sources, but the radiation-induced E′ signals of quartz from loess were obviously increased after exposure to sunlight and ultraviolet lamp. With the help of crystal defect theory, we give an explanation for the increase of E′ center ESR signals in quartz grains from loess, while E′ center signals in quartz from fault are strictly on the same level corresponding to the exposure to sunlight and other light sources.

Investigation of Nanocrystalline SnO2 by Electron Spin Resonance

Electron spin resonance studies of nanocrystalline SnO2 indicated that the experimental spectrum can be decomposed into two spectra attributed to crystalline and interfacial components respectively. The results confirmed the proposed two components model of nanocrystalline materials.

Study on comparison of ESR dating of coral and shells with 230Th/234U and 14C methods

Abstract The ESR technique was available to date samples of coral and shells. The signal at g = 2.0007 seems to be suited for this task. ESR age of the coral sample at South Sea is 4.09 ± 0.61 ka, which is within the range of 5.0 ± 0.2 and 3.75 ± 0.19 supplied by the 230 Th/ 234 U and 14 C methods, respectively, being somewhat nearer to the 14 C age. ESR age of the shell at Baoyu island is 1.66 ± 0.25 ka by the exponential fit as given according to the occurrence of saturation of ESR intensity vs added γ-ray dose. It is concordant with the value 1.69 ± 0.09 ka ( 14 C). The other two shells from the upper and low layers of Baishakou sand barrier gave ESR ages of 3.90 ± 0.59 and 7.94 ± 0.95 ka, respectively, which compare with those of 3.77 ± 0.10 and 6.83 ± 0.12 ka, respectively, given by the 14 C method.

EPR of BiSrCaCu2Oy high Tc superconductor

Abstract The EPR of the nominal BiSrCaCu 2 O y high T c superconductor at different temperatures is investigated. It is found that there are two EPR signals with different behaviors in this sample. One of them shifts gradually toward higher magnetic field and its Lande factor g -value is decreased from 2.78 to 2.24 when the temperature is raised from 115 K to 310 K. The resonance magnetic field of another signal is almost independent of temperature and its g -value is close to one of free electron. There is only zero field signal below T c for this sample and its intensity is increased with decreasing temperature. We propose a possible interpretation for these phenomena based on electron transfer between copper ion and oxygen ion in CuO plane.

Applications of ESR dating and18O Paleotemperature data for studies on Quaternary sea-level changes

Electron Spin Resonance (ESR) dating is a relatively new technique applicable also to the dating of materials from littoral zones and shallow sea regions, such as shells, corals, bones and teeth, foraminifera, diatoms, etc. ESR dating can span the time interval between the older limit of14C dating and the younger limit of the K−Ar dating, an interval of 103–106 years. Therefore, ESR technique is very suitatie for the measurement of the age of Quaternary sea—level changes. This paper gives some samples’ results by ESR dating from Early Pleistoncene to Holocene.The Quaternary sea—level changes in China were mainly eustatisms that corresponded to the paleotemperature variation. We have just begun study on the18O Paleotemperature in our continental area. Preliminary results show the temperature curve of the stalagmitic growth in caves corresponds well to the sea—level changes in 76–55×103 years B. P. ESR dating and studies of the18O Paleotemperature in East China will raise studies on Quaternary sea—level changes to a higher scientific basis.

The improved schematic band model for ESR and TL dating

Abstract In this paper we review several important concepts in the modeling of ESR and TL dating from the optical processes in the solid state, such as the activation energy, the trap depth, and the kinetics of recombination. With models based on the monomolecular process and the bimolecular process, we elaborate on the TL process and explain anomalous fading. We also discuss some problems related to ESR and TL dating in terms of solid-state physics.