Paper II: The interpretation of measurement-time-dependent single-aliquot equivalent-dose estimates using predictions from a simple empirical model

Narrow spectrum (blue-green) laboratory partial bleaching of aliquots of natural sedimentary quartz has been shown to have a significant effect on equivalent dose (measured using a single aliquot procedure) calculated as a function of measurement time (D_e(t)). A simple model, based on empirical data, is presented in which the effects of partial bleaching on D_e(t) are predicted, taking into account the influences of pre- and post-burial doses. The model is applied to the case of heterogeneous populations of partially bleached single grains with various ranges of residual doses. Modelling shows that under realistic conditions, D_e histogram plots are unable to distinguish between samples having age overestimates and those with correct ages, whereas the proposed D_e–Z plot is able to make this distinction. Furthermore, modelling shows that D_e–Z plots can identify sub-populations of grains/aliquots that show most evidence of full bleaching, which can then be used to estimate a correct mean D_e value.     

Paper I: The use of measurement-time dependent single-aliquot equivalent-dose estimates from quartz in the identification of incomplete signal resetting

The identification of incomplete signal re-setting of optically stimulated luminescence signals in sedimentary quartz is a vitally important step in the continued improvement of optical dating. It is shown that narrow spectrum (blue-green) laboratory partial bleaching of aliquots of natural sedimentary quartz has a significant effect on equivalent dose (measured using a single aliquot procedure) calculated as a function of measurement time (D_e(t)). The blue-green stimulation spectrum mimics that found underwater and the results suggest that incomplete re-setting of waterlain sediments may be possible using the D_e(t) method.     

Luminescence sensitivity changes of polymineral fine grains during IRSL and [post-IR] OSL measurements

Sensitivity changes during measurement sequences of infra-red-stimulated luminescence (IRSL) and post-IR optically stimulated luminescence (OSL) are presented for a sample of loess from northwestern China. Together with a dose recovery experiment, the results are used to investigate the ratio of 2.4 found for the D_e values (for IRSL and [post-IR] OSL) obtained when using a single-aliquot regenerative-dose (SAR) protocol in which both D_e values are obtained in a single sequence of measurements. Responses to test doses for both the IRSL and [post-IR] OSL show progressive luminescence sensitivity changes with repeated measurement cycles, with a slight dose dependence for the IRSL. In addition, five modified SAR procedures were used, varying preheats, filter combinations and method of measuring the luminescence signal. The D_e values for all IRSL measurements were at least 50% greater than those for the [post-IR] OSL signal. A modified SAR sequence was also applied in which 0.1 s stimulations (using both IR and blue light sources) were made between all sample treatments. A lack of consistency in the measured luminescence sensitivity of the natural IRSL signal suggests that the [post-IR] OSL signal provides the more reliable value of D_e.     

SnO分子的X~1∑~+,a~3Π和A~1Π态的势能曲线与光谱性质

对O原子以aug-cc-pvTZ为基组,Sn原子以aug-cc-pvTZ-PP为基组,分别采用多参考组态相互作用方法(MRCI)及运用Davidson修正的多参考组态相互作用方法对SnO分子基态X~1Σ~+及两个激发态a~3Π和A~1Π态的势能曲线进行计算,进而得到了各态的平衡键长R_e,谐振频率w_2,非谐振常数ω_ex_e,转动常数B_r,垂直跃迁能T_e以及离解能D_e,通过群论原理确定了各电子状态和离解通道,计算结果表明:3个电子态有共同的离解通道,即Sn(~3p)+O(~3p);利用Level程序对势能曲线进行拟合得到的光谱数据表明,MRCI方法的计算结果与实验值符合更好;通过求解核运动的Schrodinger方程得到了J=0时这三个电子态的前30个振动态的B_v和D_v等分子常数和振动能级E。     

Quartz from southern Africa: sensitivity changes as a result of thermal pretreatment

Sensitivity changes are known to occur in quartz during luminescence measurement procedures. Accurate single-aliquot equivalent dose (D_e) evaluations can be made only if the experimental procedure applied causes no sensitivity change, or can correct for it. The quartz single-aliquot regenerative-dose (SAR) protocol developed by Murray and Wintle (Murray, A.S., Wintle, A.G., 2000. Luminescence dating of quartz using an improved single-aliquot regenerative-close protocol. Radiation Measurements 32, 57–73) incorporates a sensitivity correction procedure that was developed using measurements made on a single sample from Australia. This paper presents experimental data designed to test the applicability of this correction procedure to quartz extracted from two southern African sediments. The results indicate that accurate corrections are made using this protocol irrespective of the direction and magnitude of the sensitivity change. The implications for routine D_e evaluation are discussed.     

Binding energy of the donor impurities in GaAs-Ga_(1-x)Al_xAs quantum well wires with Morse potential in the presence of electric and magnetic fields

The behavior of a donor in the GaAs–Ga_(1-x)Al_xAs quantum well wire represented by the Morse potential is examined within the framework of the effective-mass approximation. The donor binding energies are numerically calculated for with and without the electric and magnetic fields in order to show their influence on the binding energies. Moreover, how the donor binding energies change for the constant potential parameters(De, re, and a) as well as with the different values of the electric and magnetic field strengths is determined. It is found that the donor binding energy is highly dependent on the external electric and magnetic fields as well as parameters of the Morse potential.     

Internuclear potential for the B state of N2

The present method of finding the potential from spectroscopic data is tested in the irregular B state of N⁺₂. The turning points were introduced as parameters which were adjusted to give the experimental E_ν and B_ν accurately. The predicted values of r_e and D_e are quite satisfactory.     

75As32S+和75As34S+离子的光谱常数与分子常数

采用内收缩多参考组态相互作用(MRCI)方法, 结合Dunning系列相关一致基, 分别对⁷⁵As³²S⁺和⁷⁵As³⁴S⁺离子的X³Σ^-和A¹Π电子态的势能曲线进行了计算, 进一步拟合势能曲线, 得到各电子态的光谱常数与分子常数. 首先, 采用MRCI方法结合相关一致基, aug-cc-pV5Z, 对AsS⁺离子的X³Σ^-和A¹Π 电子态进行了计算, 获得相应的势能曲线; 然后, 为进一步提高势能曲线的精度, 对其进行了三种修正计算. 采用Davidson(+Q)方法修正MRCI 方法计算过程中存在的基组大小不一致缺陷; 利用二阶Douglas-Kroll哈密顿近似, 在cc-pVQZ基组水平, 修正了相对论效应对势能曲线的影响; 利用两点能量外推法, 在aug-cc-pVQZ和aug-cc-pV5Z基组水平对各能量点的势能值进行了外推, 得到完全基组极限处的势能曲线. 最后, 利用修正(包括Davidson修正、相对论修正和基组外推)后的势能曲线, 通过Vibrot程序, 求解双原子分子核运动的径向Schrödinger方程, 并进行同位素质量识别, 得到⁷⁵As³²S⁺和⁷⁵As³⁴S⁺离子两个电子态的光谱常数(T_e, R_e, ω_e, ω_ex_e, α_e 和B_e)和分子常数(G(ϒ), B_v, D_v).     

LiAl分子基态、激发态势能曲线和振动能级

利用单双激发多参考组态相互作用方法获得了LiAl分子基态X¹∑⁺及七个激发态a³∏, A¹∏, b³∑⁺, c³∑⁺, B¹∏, C¹∑⁺, d³∏的势能曲线, 通过势能曲线得到各态的平衡核间距R_e, 进而求得绝热激发能和垂直激发能.计算结果表明:c³∑⁺ 电子态是一个不稳定的排斥态, A¹∏态是一个较弱的束缚态, 其余6个电子态均为束缚态; b³∑⁺与 c³∑⁺态之间存在预解离现象; 8个电子态分别解离到两个通道, 即Li(²S)+Al(²P⁰)与Li(²P⁰)+Al(²P⁰). 接着将势能曲线拟合到Murrel-Sorbie解析势能函数形式, 据此获得各态的光谱数据:基态X¹∑⁺的平衡键长为0.2863 nm, 谐振频率为316 cm^-1, 解离能D_e为1.03 eV, 激发态a³∏, A¹∏, b³∑⁺, c³∑⁺, B¹∏, C¹∑⁺, d³∏的垂直激发能依次为0.27, 0.83, 1.18, 1.14, 1.62, 1.81, 2.00 eV; 解离能依次为1.03, 0.82, 0.26, 排斥态, 1.54, 1.10, 0.93 eV, 相应谐振频率 ω_e为339, 237, 394, 排斥态, 429, 192, 178 cm^-1. 通过求解核运动的薛定谔方程找到了J=0时 LiAl分子7个束缚电子态的振动能级和转动惯量. 关键词： LiAl 光谱常数 势能曲线 振动能级     

PS自由基X2Π态的势能曲线和光谱性质

采用Davidson修正的内收缩多参考组态相互作用方法(icMRCI+Q) 结合Dunning等的相关一致基计算了PS自由基X²Π 态势能曲线. 利用三阶Douglas-Kroll Hamilton近似结合cc-pV5Z相对论收缩基进行了相对论修正计算. 利用aug-cc-pCV5Z基组对势能曲线进行了核价相关修正计算, 并将总能量外推至完全基组极限. 拟合得到了X²Π态的主要光谱常数R_e, ω_e, ω_ex_e, ω_ey_e, B_e, α_e 和D_e, 与实验结果符合较好. 利用Breit-Pauli算符, 研究了旋轨耦合效应对势能曲线的影响, 得到了两条Ω 态的势能曲线. 详细分析了在旋轨耦合计算中, 核电子相关与冻结核近似对电子结构和光谱性质的影响. 在icMRCI+Q/56+DK+CV+SO理论水平上得到了两个Ω 态的主要光谱常数T_e, R_e, ω_e, ω_ex_e, ω_ey_e, B_e 和α_e, 结果与实验结果一致. 在平衡位置处, 本文的X²Π态旋轨耦合能量分裂值为 323.73 cm^-1, 与实验结果321.93 cm^-1较为一致. 通过求解双原子分子核运动的径向Schrödinger方程, 找到了无转动PS自由基X²Π态及其两个Ω 态的全部振动态, 还分别计算了它们相应的振动能级和惯性转动常数等分子常数, 这些结果与已有的实验值一致. 关键词： 势能曲线 光谱常数 分子常数 旋轨耦合     

Na_2~+离子较低电子态势能曲线和光谱常数的理论研究

通过多组态相互作用方法,结合原子有效芯势与极化势,利用非收缩的高斯基函数,计算了Na_2~+分子对应最低9个解离限的36个电子态的势能曲线.基于计算获得的束缚态势能曲线,拟合给出了相应的光谱常数,并与已有的实验和理论结果进行了比较.同时,给出了部分电子态的振动-转动能级和一些同类态避免交叉点的信息.计算获得的光谱信息对冷原子分子光谱与动力学的研究具有参考价值.     

Theoretical studies of spin-Hamiltonian parameters for Ni ions in CsMgX3 (X=Cl, Br, I) crystals from the two-mechanism model

In this paper, the high-order perturbation formulas of spin-Hamiltonian (SH) parameters (g factors g, g and zero-field splitting D), including both the crystal-field (CF) and for the first time charge-transfer (CT) mechanisms, are established for 3d⁸ ions in trigonal octahedral clusters. By using these formulas, the SH parameters of Ni²⁺ ions in CsMgX₃ (X=Cl, Br, I) crystals are calculated. The results are consistent with the experimental values. The calculations suggest that the sign of Q^CT (Q=Δg, Δg or D, where the g-shift Δg_i=g_i−g_e, g_e≈2.0023 is the value of free-electron) due to CT mechanism is the same as that of the corresponding Q^CF due to CF mechanism, and the relative importance of CT mechanism (characterized by Q^CT/Q^CF) increases with the increasing atomic number of ligand X. So, for the 3dⁿ ML_m clusters with ligand having large atomic number, the reasonable theoretical explanations of all SH parameters should take both CF and CT mechanisms into account. The defect structure of (NiX₆)⁴⁻ impurity centers in CsMgX₃:Ni²⁺ crystals is also considered in our model.     

SN-分子离子的势能函数和光谱常数研究

采用耦合簇CCSD(T)方法结合系列相关一致基组aug-cc-pVXZ (X=D,T,Q,5) 对基态SN^-分子离子(X³∑^-) 进行了结构优化和单点能扫描计算. 用四种方法进行基组外推得到该体系的平衡核间距R_e=0.15852 nm, 谐振频率ω_e=948.05 cm^-1, 离解能D_e=3.934 eV均与实验数据符合得很好. 对单点能扫描结果用9参数Murrell-Sorbie势能函数进行了最小二乘拟合, 得到了体系的解析势能函数表达式, 并进一步推导出了体系的力常数和光谱常数. 拟合所得势能曲线准确地再现了SN^-分子离子的离解能和平衡结构特征. 通过求解核运动的径向薛定谔方程, 得到了无转动SN^- (X³∑^-) 的全部振动态, 并进一步计算出了各振动能级相应的分子常数. 与实验结果及其他理论研究结果的对比表明, 本文关于SN^-分子离子平衡常数和光谱常数的计算结果达到了较高的精度, 能为进一步的实验探测和理论研究提供参考依据. 关键词： 势能曲线 解析势能函数 光谱常数 振动能级     

Spectral spin diffusion and magnetic dipolar energy in the NMR of 13CH3 compounds

Spin diffusion between ¹³CH₃ groups in solids is studied both theoretically and experimentally. It is shown to be dominated by mutual spin flip–flops of protons belonging to neighbouring methyl groups. Also nonmethyl protons may contribute significantly if present in the sample. The spin–rotational ground state of ¹³CH₃ consists of 16 sublevels. When their populations are used to describe spin diffusion, eight population combinations are shown to be important, two of them corresponding to the ¹³C–proton and proton–proton intra-methyl magnetic dipolar energies, D_c and D_p, respectively. Spin-diffusion transitions modulate these combinations so that a further reduction to two sets of four combinations is possible, with no coupling between the sets. Coupled differential equations are derived to describe the time dependence of the combinations in each set. They are solved numerically and compared with experimental results on a single crystal of aspirin with ¹³C-labelled methyl groups at the carbon resonance. The ¹³C NMR induction signal was observed as a function of time after the preparation either at the carbon resonance (a two-pulse sequence) or at the proton resonance (proton saturation). Usually carbon spectra were computed first and then three of the mentioned population combinations were obtained from the individual spectral components. Some results on the time dependence of D_c were also obtained directly from the amplitude of the out-of-phase induction signal. Theoretical predictions are found to describe semiquantitatively the overall time dependence of these three combinations and especially their variation with different initial conditions, which are discussed in detail. Also the partial transfer of the magnetic dipolar energy between D_c and D_p is nicely explained. Reasons for discrepancies are discussed.     

Investigations of the performance of quartz single aliquot DE determination procedures

Over the past few years a variety of equivalent dose (D_E) determination techniques for quartz, which are truly single aliquot-based, have been proposed. Such methods avoid the need for inter-aliquot normalisation, and provide considerable improvements in the precision of equivalent dose (D_E) estimates. Much of the research leading to these developments have been based on detailed investigations of a few samples, primarily from Australia. All ’protocols’ developed have performed impressively. It is necessary, however, to verify the consistency of the single aliquot D_E determination methods on a wide range of samples before they can be considered as prescribed or standard. We have analysed approximately 100 samples from a range of sedimentary environments and geological provinces in an attempt to confirm the robustness of the single aliquot techniques. Up to 65% of samples measured in our laboratory were not suited to analysis via application of single aliquot additive dose (SAAD) procedures. This relates to a range of factors, including lack of sample sensitivity and dose dependent sensitivity changes. Furthermore, we have observed some problems in dating young sediments using single aliquot regeneration (SAR) methods. Critically, we observe that sample to sample variability on quartz luminescence (thermally- and optically-stimulated) behaviour is considerable, and many samples are found to exhibit behaviour which contrasts greatly from that described in recent phenomenological studies.     

Observations of thermal transfer OSL signals in glacigenic quartz

The conclusions of Rhodes and Pownall (Rhodes, E.J., Pownall, L., 1994. Zeroing of the OSL signal in quartz from young glaciofluvial sediments. Radiation Measurements 23, 329–333) were somewhat discouraging for the prospects of using quartz OSL for dating glacigenic sediments, while the more detailed study of Rhodes and Bailey (Rhodes, E.J., Bailey, R.M., 1997. The effect of thermal transfer on the zeroing of the luminescence of quartz from recent glaciofluvial sediments. Quaternary Science Reviews (Quaternary Geochronology) 16, 291–298) provided more encouragement. Specifically, the latter authors were able to account for the relatively high D_e values observed for recent glacigenic (dominantly glaciofluvial) sediments in terms of an anomalously high thermal transfer effect, rather than simply insufficient bleaching prior to deposition. In other locations, the OSL of quartz from glacigenic material appears to provide reliable age estimates, and does not suffer from these effects (Owen, L.A., Richards, B., Rhodes, E.J., Cunningham, W.D., Windley, B.F., Badamgarav, J., Dorjnamjaa, D., 1998. Relic permofrost structures in the Gobi of Mongolia: age and significance. Journal of Quaternary Science 13 (16), 539–548; Richards, B.W., Owen, L.A., Rhodes, E.J., 2000. Timing of Late Quaternary glaciations in the Himalayas of northern Pakistan. Journal of Quaternary Science 15, 283–297). In this paper, laboratory bleached samples from both the above studies are remeasured, using an experimental design to correct for OSL sensitivity changes, which has some similarities to the single aliquot regenerative dose (SAR) protocol of Murray and Wintle (Murray A.S., Wintle A.G., 2000. Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol. Radiation Measurements 32, 57–73). Clear evidence of thermal transfer OSL signals, generated during the preheating procedure, is presented. Further measurements, using the full SAR protocol, demonstrate that the source of this charge is related to natural dosing. For one sample, the apparent effect is subtracted effectively by the SAR protocol. Another sample studied in detail shows a striking relationship between the thermally transferred OSL signal and the total TL observed during the ramping of the preceding preheat treatment.     

~6Li原子跃迁频率和超精细分裂的精密测量

本文实现了可用于锂原子频率精密测量的冷原子系统,获得了大数目的原子样品;利用西西弗斯冷却和速度选择相干布居俘获实现了~6Li的冷原子的灰色黏胶冷却,原子的温度被冷却到多普勒冷却极限以下,达到50μK;利用光学频率梳,实验上测量了D1线的跃迁频率和超精细分裂,测量结果和理论计算相接近,可以和目前最精确的测量相比较.这些测量为进一步的轻质量原子频率的精密测量、α常数以及核半径的精确标定打下了基础.     

Joule–Thomson expansion of higher dimensional nonlinearly AdS black hole with power Maxwell invariant source

In this paper, the Joule–Thomson expansion of the higher dimensional nonlinearly anti-de Sitter(Ad S) black hole with power Maxwell invariant source is investigated. The results show the Joule–Thomson coefficient has a zero point and a divergent point, which coincide with the inversion temperature Tiand the zero point of the Hawking temperature, respectively. The inversion temperature increases monotonously with inversion pressure. For the high-pressure region, the inversion temperature decreases with the dimensionality D and the nonlinearity parameter s, whereas it increases with the charge Q. However, Tifor the low-pressure region increase with D and s, while it decreases with Q. The ratio ηBHbetween the minimum inversion temperature and the critical temperature does not depend on Q, it recovers the higher dimensional Reissner–N?rdstrom Ad S black hole case when s = 1. However, for s 1, it becomes smaller and smaller as D increases and approaches a constant when D →∞. Finally, we found that an increase of mass M and s, or reducing the charge Q and D can enhance the isenthalpic curve, and the effect of s on the isenthalpic curve is much greater than other parameters.     

Dynamic contribution to the fishtail effect in a twin-free DyBa2Cu3O7−δ single crystal

Superconducting current densities j_s and dynamic relaxation rates Q d ln j_s/d In(dB_e/dt), where dB_e/dt is the sweep rate of the external magnetic field B_e, were measured as a function of temperature (5 K < T < 65 K) in magnetic fields up to 7 T on a twin-free DyBa₂Cu₃O_7−δ single crystal by means of a high-sensitivity capacitance torque magnetometer. Above 15 K, we observe a “fishtail” effect, i.e. a pronounced minimum in the j_s(B_e) curve at fields around B_e = 1 T. The relaxation rate Q shows an anomalous increase at low fields which is correlated to the minimum in the j_s(B_e) curve. Both the j_s versus B_e and Q versus B_e data are used as input parameters into the generalized inversion scheme developed by Schnack et al. [Phys. Rev. B 48 (1993) 13178] to calculate the true critical current density j_c which is by definition independent of relaxation effects. Interestingly, the j_c(B_e, T) curves derived in this way do not show a minimum. This points clearly to a dynamic contribution to the fishtail effect. The true critical current density j_c(B_e, T) decreases weakly with increasing B_e over the entire measured temperature and field range, as expected for single-vortex pinning. This indicates that the observed fishtail effect is not caused by a crossover from single-vortex pinning to pinning of flux bundles. The temperature dependence of j_c is in good agreement with the predictions of a model based on single-vortex pinning caused by spatial fluctuations in the charge-carrier mean free path.     

D-T2二维核磁共振脉冲序列及反演方法改进设计

面对日益复杂的勘探对象, D-T₂二维核磁共振技术在实际应用中面临无法兼顾扩散系数测量范围和横向弛豫分辨率的困境. 脉冲序列作为D-T₂二维核磁共振数据采集的核心技术, 其性能优劣直接影响应用效果, 在综合对比PFG, STE-PFG, BP-PFG、改良式CPMG, 扩散编程, 多回波间隔CPMG脉冲序列性能的基础上, 有效融合脉冲梯度场、恒定梯度场D-T₂脉冲序列的优点, 本文提出一种基于脉冲梯度场的双变量、两窗口D-T₂脉冲序列改进设计. 针对两个窗口的D-T₂二维核磁共振数据反演, 为突破现有反演方法无法兼顾反演精度和解谱效率的瓶颈, 本着第二个窗口回波信号为主、第一个窗口回波信号为辅的原则, 本文提出一种同时使用两个窗口数据参与解谱的联合TSVD反演方法. 气水、油水、稠油、油气水模型不同信噪比条件下的数值模拟结果表明, 本文提供的D-T₂改进脉冲序列达到了平衡扩散系数测量范围和横向弛豫分辨率的设计要求, 本文提供的联合TSVD反演方法也有效平衡了反演精度要求和解谱效率. 文中的D-T₂改进脉冲序列及联合TSVD反演方法在复杂油气藏流体识别和产能预测中具有广泛的应用前景, 可为促进国内D-T₂二维核磁共振岩心分析技术的发展提供有利条件.