Parameter analysis for a nuclear magnetic resonance gyroscope based on ~(133)Cs–~(129)Xe/~(131)Xe

We theoretically investigate several parameters for the nuclear magnetic resonance gyroscope based on ~(133)C_(s–)~(129)Xe/~(131)Xe. For a cell containing a mixture of ~(133)Cs at saturated pressure, we investigate the optimal quenching gas(N_2) pressure and the corresponding pump laser intensity to achieve 30% ~(133)Cs polarization at the center of the cell when the static magnetic field B0 is 5 μT with different ~(129)Xe/~(131)Xe pressure. The effective field produced by spin-exchange polarized ~(129)Xe or ~(131)Xe sensed by ~(133)Cs can also be discussed in different~(129)Xe/~(131)Xe pressure conditions. Furthermore,the relationship between the detected signal and the probe laser frequency is researched. We obtain the optimum probe laser detuning from the D2(6~2S_(1/2)→ 6~2P_(3/2)) resonance with different ~(129)Xe/~(131)Xe pressure owing to the pressure broadening.     

On the low frequency characteristics of head-related transfer function

A method to correct the measured head-related transfer functions （HRTFs） at low frequency was proposed. By analyzing the HRTFs from the spherical head model at low frequency, it is proved that below the frequency of 400 Hz, magnitude of HRTF is nearly constant and the phase is a linear function of frequency both for the far and near field. Therefore, if the HRTFs above 400 Hz are accurately measured by experiment, it is able to correct the HRTFs at low frequency by the theoretical model. The results of calculation and subjective experiment show that the feasibility of the proposed method.     

MEASUREMENTS OF 129Xe NUCLEAR MAGNETIC RESONANCE IN GASEOUS, LIQUID AND SOLID XENON

Natural xenon, contained in a ceil at a pressure of 6.5 atm, is frozen from 303 to 137 K on an WP-80SY NMR spectrometer. NMR signals of ¹²⁹Xe atoms in gaseous, liquid and solid phases are measured at various temperatures, We found that the chemical shift of NMR signal of liquid ¹²⁹Xe (expressed as ΔH) is directly proportional to the density of the sample with a coefficient of (4.73±0.05)×10^-7; and the chemical shift of NMR signal of solid ¹²⁹Xe (expressed as ΔH) is nearly proportional to the density of the sample with a coefficient of (5.00±0.08)×10^-7.     

Tunable Ba0.5Sr0.5TiO3 film bulk acoustic resonators using SiO2/Mo Bragg reflectors

Tunable and switchable Ba 0.5 Sr 0.5 TiO 3 film bulk acoustic resonators（FBARs） based on SiO 2 /Mo Bragg reflectors are explored,which can withstand high temperature for the deposition of Ba x Sr 1 x TiO 3（BST） films at 800 C.The dc bias-dependent resonance may be attributed to the piezoelectricity of the BST film induced by an electrostrictive effect.The series resonant frequency is strongly dc bias-dependent and shifts downwards with dc bias increasing,while the parallel resonant frequency is only weakly dc bias-dependent and slightly shifts upwards at low dc bias（ 45 V） while downwards at higher dc bias.The calculated relative tunability of shifts at series resonance frequency is around 2.3% and the electromechanical coupling coefficient is up to approximately 8.09% at 60-V dc bias,which can be comparable to AlN FBARs.This suggests that a high-quality tunable BST FBAR device can be achieved through the use of molybdenum（Mo） as the high acoustic impedance layer in a Bragg reflector,which not only provides excellent acoustic isolation from the substrate,but also improves the crystallinity of BST films withstanding higher deposition temperature.     

Imaginary Part of the Surface Tension of Water

We report a direct measurement of the imaginary part of the surface tension of water through a dynamic scheme using a thin vertical glass fiber of diameter of 3 tun with one end glued onto a cantilever beam and the other end touching a water-air interface. The frequency dependence of the dissipation factor experienced by the glass fiber is exactly calculated through measuring the phase delay with various frequencies when the glass fiber is forced to oscillate vertically. We find the same intercept at the dissipation factor axis for different frequency dependences of the dissipation factor for different depths by which the glass fiber is dipped into water. This nonzero dissipation factor at zero frequency presents direct evidence of the existence of the imaginary part of surface tension of water and yields a complex surface tension of water σ^＊ = 0.073 ＋ i（0.017 ± 0.002） N/m at room temperature.     

Simulation and measurement of the resonant Schottky pickup

A resonant Schottky pickup with high sensitivity, built by GSI, will be used for nuclear mass and lifetime measurement at CSRe. The basic concepts of Schottky noise signals, a brief introduction of the geometry of the detector, the transient response of the detector, and MAFIA simulated and perturbation measured results of characteristics are presented in this paper. The resonant frequency of the pickup is about 243 MHz and can be slightly changed at a range of 3 MHz. The unloaded quality factor is about 1072 and the shunt impedance is 76 kΩ. The measured results of the characteristics are in agreement with the MAFIA simulations.     

Magnetoelectric Coupling in Bilayers of Pb（Zr, Ti）O3 Epoxy and Hot Pressed Manganite Perovskite

The synthesis and magnetoclectric （ME） characterization of bilayers of Pb（Zr, Ti）O3 （PZT） and hot pressed manganite perovskite La0.7Sr0.3MnO3 （LSMO） are discussed. Very strong ME interactions are measured for the bilayers. The bilayers exhibit superior ME coupling compared to thick-film composites prepared by tape casting process. Data of the ME voltage coefficient have been obtained as functions of bias magnetic field H, temperature and frequency. The transverse coupling is stronger than the longitudinal interactions and a maximum in the ME voltage coefficient is measured at 225K. The frequency dependence of the ME voltage coefficient reveals a peak at the electromechanical resonance due to radial modes.     

MEASUREMENTS OF 129Xe NUCLEAR MAGNETIC RESONANCE IN GASEOUS,LIQUID AND SOLID XENON

Natural xenon, contained in a ceil at a pressure of 6.5 atm, is frozen from 303 to 137 K on an WP-80SY NMR spectrometer. NMR signals of ¹²⁹Xe atoms in gaseous, liquid and solid phases are measured at various temperatures, We found that the chemical shift of NMR signal of liquid ¹²⁹Xe (expressed as ΔH) is directly proportional to the density of the sample with a coefficient of (4.73±0.05)×10^-7; and the chemical shift of NMR signal of solid ¹²⁹Xe (expressed as ΔH) is nearly proportional to the density of the sample with a coefficient of (5.00±0.08)×10^-7.     

A New Quantum Key Distribution Scheme Based on Frequency and Time Coding

A new scheme of quantum key distribution （QKD） using frequency and time coding is proposed, in which the security is based on the frequency-time uncertainty relation. In this scheme, the binary information sequence is encoded randomly on either the centrM frequency or the time delay of the optical pulse at the sender. The central frequency of the single photon pulse is set as w1 for bit 0 and set as w2 for bit 1 when frequency coding is selected. However, the single photon pulse is not delayed for bit 0 and is delayed in τ for 1 when time coding is selected. At the receiver, either the frequency or the time delay of the pulse is measured randomly, and the final key is obtained after basis comparison, data reconciliation and privacy amplification. With the proposed method, the effect of the noise in the fiber channel and environment on the QKD system can be reduced effectively.     

流动系统中的激光增强固体和液体129Xe核磁共振信号

在流动系统中,用半导体阵列激光器在低磁场下抽运Cs原子,由自旋交换碰撞产生极化的129Xe气体,在SY80M核磁共振谱仪中,冻成固体和液体后的极化度分别为216%和145%,和相同条件下未光泵的129Xe极化度相比,分别增强6000和5000倍.为将激光增强固体和液体129Xe用于量子计算提供了基础和可能.并对输运和相变过程中极化损失作了讨论 关键词： 光泵 激光极化 核磁共振信号 光和原子相互作用     

129Xe contact shift in oxygen gas

We have determined the temperature dependence of σ₁ of ¹²⁹Xe in oxygen gas. These results were obtained by measurement of the resonance frequency of ¹²⁹Xe in gas samples of known densities in Xe and O₂. The shift of the resonance frequency due to Xe-Xe interactions has been measured in pure Xe gas samples with improved precision. This allows the determination of σ₁(Xe-O₂) by subtracting out the known effect of Xe-Xe interactions in mixed Xe-O₂ samples. σ₁(Xe-O₂) values are reported here for the temperature range 220 to 440 K. The values of σ₁(Xe-O₂) are adequately described by the polynomial function in p.p.m. amagat^-1 σ₁(Xe-O₂) = - 1·061 + 3·64 × 10^-3τ - 2·19 × 10^-5τ² + 9·58 × 10^-8τ³ - 2·08 × 10^-10τ⁴, where τ = (T - 300 K). It is found that the temperature dependence of σ₁(Xe-O₂) can be interpreted in terms of a contact interaction between Xe and the paramagnetic O₂ molecule.     

Nuclear Spin Maser Oscillation of 129Xe by Means of Optical-Detection Feedback

We have developed the nuclear spin maser oscillating at a low frequency of 34 Hz with highly polarized nuclear spins of the noble gas element ¹²⁹Xe. The system is advantageous for detecting a small frequency shift of the nuclear spin precession. We are thus planning to apply this system to the search for an atomic electric dipole moment of ¹²⁹Xe. We here report the development of the system and its performance.     

Nuclear spin maser and experimental search for 129 Xe atomic EDM

The present status of an active spin maser which is being developed for an experimental search for ¹²⁹Xe atomic electric dipole moment (EDM) is presented. In order to realize the long term stability of maser frequency, systematic effects for the spin maser operation were investigated. The correlations in the maser frequency with the solenoid current, the environmental field and the cell temperature were found. With the solenoid current and environmental field being stabilized and the cell temperature lowered, a frequency precision of 7.9 nHz has been achieved for the maser operation.     

129Xe NMR study of Xe adsorption on multiwall carbon nanotubes

¹²⁹Xe NMR spectroscopy has been used to study the adsorption of Xe on multi-wall carbon nanotubes (MWCNT). The results obtained have shown the ¹²⁹Xe NMR ability to probe the intercrystalline (aggregate) and the inner porosity of CNT. In particular, the effects on porosity of tubes openings by hydrogen exposure and of ball milling were examined. Dramatic changes observed in the ¹²⁹Xe NMR spectra after moderate ball milling of MWCNTs were attributed to the destruction of the initial intercrystalline pore structure and to the Xe access inside the nanotubes. To examine the exchange dynamics the mixture of as-made and milled MWCNTs was studied with one- and two-dimensional (1D and 2D) ¹²⁹Xe NMR. The exchange between the interior of milled nanotubes and the aggregate pores of as-made MWCNTs was fast on the NMR acquisition time scale. The Xenon exchange between the interior of the as-made MWCNTs and the large aggregate pores occurred on a longer time scale of 10 ms, as was established by 2D ¹²⁹Xe NMR exchange spectroscopy. Variable temperature ¹²⁹Xe NMR data were also discussed and analyzed in terms of the fast exchange approximation.     

Parameter analysis for a nuclear magnetic resonance gyroscope based on bf133Cs-129Xe/131Xe

We theoretically investigate several parameters for the nuclear magnetic resonance gyroscope based on ¹³³Cs-¹²⁹Xe/¹³¹Xe. For a cell containing a mixture of ¹³³Cs at saturated pressure, we investigate the optimal quenching gas (N₂) pressure and the corresponding pump laser intensity to achieve 30% ¹³³Cs polarization at the center of the cell when the static magnetic field B₀ is 5 μT with different ¹²⁹Xe/¹³¹Xe pressure. The effective field produced by spin-exchange polarized ¹²⁹Xe or ¹³¹Xe sensed by ¹³³Cs can also be discussed in different ¹²⁹Xe/¹³¹Xe pressure conditions. Furthermore, the relationship between the detected signal and the probe laser frequency is researched. We obtain the optimum probe laser detuning from the D2 (6²S_1/2→6²P_3/2) resonance with different ¹²⁹Xe/¹³¹Xe pressure owing to the pressure broadening.     

New excited states of the nucleus129Xe

Excited states of¹²⁹Xe have been investigated through the¹²⁶Te(α,n)¹²⁹Xe reaction at the incident energy E=16MeV by means of in-beam gamma ray spectroscopy. Numerous levels below the excitation energy of 2.5MeV were found. Spin assignments were made from side feeding excitation functions. A new level at 274.2keV, which is suggested as spin 9/2 negtive parity bandhead, was observed for the first time.     

Laser-polarized (129)Xe NMR and MRI at ultralow magnetic fields

Laser-polarized (129)Xe and a high-T(c)superconducting quantum interference device (SQUID) are used to obtain magnetic resonance images in porous materials at a magnetic field of 2.3 mT, corresponding to a Larmor frequency of 27 kHz. Image resolution of 1 mm is obtained with gradients of only 1 mT/m. The resolution of xenon chemical shifts in different physicochemical environments at ultralow fields is also demonstrated. Details of the circulating flow optical pumping apparatus and the SQUID spectrometer are presented.     

129Xe核自旋极化转移增强分子的核磁共振信号

激光极化的129Xe核具有极高的非平衡极化度和长的弛豫时间,这一特点使得它能够极化转移增强液体、固体或者固体表面分子中原子核自旋极化。因而,提高了它们的核磁共振探测灵敏度和扩展了在材料和表面科学研究中的应用。综述激光极化129Xe核与其它分子中原子核之间的极化转移研究与进展,介绍相关物理机制和参数的测量。     

Applications of laser-polarized 129Xe to biomolecular assays

The chemical shift sensitivity and significant signal enhancement afforded by laser-polarized ¹²⁹Xe have motivated the application of ¹²⁹Xe NMR to biological imaging and spectroscopy. Recent research done by our group has used laser-polarized ¹²⁹Xe in biomolecular assays that detect ligand-binding events and distinguish protein conformations. The successful application of unfunctionalized and functionalized ¹²⁹Xe NMR to in vitro biomolecular assays suggests the potential future use of a functionalized xenon biosensor for in vivo imaging.     

Relaxation of hyperpolarized 129Xe in a deflating polymer bag

In magnetic resonance imaging with hyperpolarized (HP) noble gases, data is often acquired during prolonged gas delivery from a storage reservoir. However, little is known about the extent to which relaxation within the reservoir will limit the useful acquisition time. For quantitative characterization, 129Xe relaxation was studied in a bag made of polyvinyl fluoride (Tedlar). Particular emphasis was on wall relaxation, as this mechanism is expected to dominate. The HP 129Xe magnetization dynamics in the deflating bag were accurately described by a model assuming dissolution of Xe in the polymer matrix and dipolar relaxation with neighboring nuclear spins. In particular, the wall relaxation rate changed linearly with the surface-to-volume ratio and exhibited a relaxivity of κ=0.392±0.008 cm/h, which is in reasonable agreement with κ=0.331±0.051 cm/h measured in a static Tedlar bag. Estimates for the bulk gas-phase 129Xe relaxation yielded T1bulk=2.55±0.22 h, which is dominated by intrinsic Xe-Xe relaxation, with small additional contributions from magnetic field inhomogeneities and oxygen-induced relaxation. Calculations based on these findings indicate that relaxation may limit HP 129Xe experiments when slow gas delivery rates are employed as, for example, in mouse imaging or vascular infusion experiments.