Search for Spin-Dependent Gravitational Interactions at Earth Range.

Among the four fundamental forces, only gravity does not couple to particle spins according to the general theory of relativity. We test this principle by searching for an anomalous scalar coupling between the neutron spin and the Earth's gravity on the ground. We develop an atomic gas comagnetometer to measure the ratio of nuclear spin-precession frequencies between ^{129}Xe and ^{131}Xe, and search for a change of this ratio to the precision of 10^{-9} as the sensor is flipped in Earth's gravitational field. The null results of this search set an upper limit on the coupling energy between the neutron spin and the gravity on the ground at 5.3×10^{-22} eV (95% confidence level), resulting in a 17-fold improvement over the previous limit. The results can also be used to constrain several other anomalous interactions. In particular, the limit on the coupling strength of axion-mediated monopole-dipole interactions at the range of Earth's radius is improved by a factor of 17.

Search for Monopole-Dipole Interactions at the Submillimeter Range with a

Monopole-dipole interactions involving scalar couplings between a spin and a massive particle violate both P and T symmetry, and can be mediated by axions. We use a ^{129}Xe-^{131}Xe-Rb atomic cell comagnetometer to measure the ratio of precession frequencies between the two xenon isotopes, and search for changes of the ratio correlated with the distance between the atomic cell and a nonmagnetic bismuth germanate crystal. A modulated Rb polarization scheme is used to suppress systematic effects by 2 orders of magnitude. The null results of this search improve the upper limit on the coupling strength g_{s}^{N}g_{p}^{n} over the interaction range 0.11-0.55 mm, and by a maximum improvement factor of 30 at 0.24 mm. The corresponding propagator mass range of this new excluded region covers 0.36-1.80 meV.

Measurement of the Electric Dipole Moment of

The permanent electric dipole moment (EDM) of the ^{171}Yb (I=1/2) atom is measured with atoms held in an optical dipole trap. By enabling a cycling transition that is simultaneously spin-selective and spin-preserving, a quantum nondemolition measurement with a spin-detection efficiency of 50% is realized. A systematic effect due to parity mixing induced by a static E field is observed, and is suppressed by averaging between measurements with optical dipole traps in opposite directions. The coherent spin precession time is found to be much longer than 300 s. The EDM is determined to be d(^{171}Yb)=(-6.8±5.1_{stat}±1.2_{syst})×10^{-27} e cm, leading to an upper limit of |d(^{171}Yb)|<1.5×10^{-26} e cm (95% C.L.). These measurement techniques can be adapted to search for the EDM of ^{225}Ra.

Optical Excitation and Trapping of

We have realized optical excitation, trapping, and detection of the radioisotope ^{81}Kr with an isotopic abundance of 0.9 ppt. The 124 nm light needed for the production of metastable atoms is generated by a resonant discharge lamp. Photon transport through the optically thick krypton gas inside the lamp is simulated and optimized to enhance both brightness and resonance. We achieve a state-of-the-art ^{81}Kr loading rate of 1800 atoms/h, which can be further scaled up by adding more lamps. The all-optical approach overcomes the limitations on precision and sample size of radiokrypton dating, enabling new applications in the earth sciences, particularly for dating of polar ice cores.

A Critical Review of State-of-the-Art and Emerging Approaches to Identify Fracking-Derived Gases and Associated Contaminants in Aquifers.

High-volume, hydraulic fracturing (HVHF) is widely applied for natural gas and oil production from shales, coals, or tight sandstone formations in the United States, Canada, and Australia, and is being widely considered by other countries with similar unconventional energy resources. Secure retention of fluids (natural gas, saline formation waters, oil, HVHF fluids) during and after well stimulation is important to prevent unintended environmental contamination, and release of greenhouse gases to the atmosphere. Here, we critically review state-of-the-art techniques and promising new approaches for identifying oil and gas production from unconventional reservoirs to resolve whether they are the source of fugitive methane and associated contaminants into shallow aquifers. We highlight future research needs and propose a phased program, from generic baseline to highly specific analyses, to inform HVHF and unconventional oil and gas production and impact assessment studies. These approaches may also be applied to broader subsurface exploration and development issues (e.g., groundwater resources), or new frontiers of low-carbon energy alternatives (e.g., subsurface H2 storage, nuclear waste isolation, geologic CO2 sequestration).

First Measurement of the Atomic Electric Dipole Moment of (225)Ra.

The radioactive radium-225 ((225)Ra) atom is a favorable case to search for a permanent electric dipole moment. Because of its strong nuclear octupole deformation and large atomic mass, (225)Ra is particularly sensitive to interactions in the nuclear medium that violate both time-reversal symmetry and parity. We have developed a cold-atom technique to study the spin precession of (225)Ra atoms held in an optical dipole trap, and demonstrated the principle of this method by completing the first measurement of its atomic electric dipole moment, reaching an upper limit of |d((225)Ra)|<5.0×10(-22) e cm (95% confidence).

Ion current as a precise measure of the loading rate of a magneto-optical trap.

We have demonstrated that the ion current resulting from collisions between metastable krypton atoms in a magneto-optical trap can be used to precisely measure the trap loading rate. We measured both the ion current of the abundant isotope 83Kr (isotopic abundance=11%) and the single-atom counting rate of the rare isotope 85Kr (isotopic abundance∼1×10(-11)), and found the two quantities to be proportional at a precision level of 0.9%. This work results in a significant improvement in using the magneto-optical trap as an analytical tool for noble-gas isotope ratio measurements, and will benefit both atomic physics studies and applications in the earth sciences.

Measurement of the hyperfine quenching rate of the clock transition in 171YB.

We report the first experimental determination of the hyperfine quenching rate of the 6s(2) (1)S(0)(F = 1/2) - 6s6p (3)P(0)(F = 1/2) transition in (171)Yb with nuclear spin I = 1/2. This rate determines the natural linewidth and the Rabi frequency of the clock transition of a Yb optical frequency standard. Our technique involves spectrally resolved fluorescence decay measurements of the lowest lying (3)P(0,1) levels of neutral Yb atoms embedded in a solid Ne matrix. The solid Ne provides a simple way to trap a large number of atoms as well as an efficient mechanism for populating (3)P(0). The decay rates in solid Ne are modified by medium effects including the index-of-refraction dependence. We find the (3)P(0) hyperfine quenching rate to be (4.42 ± 0.35) × 10(-2) s(-1) for free (171)Yb, which agrees with recent ab initio calculations.

Residence times of groundwater along a flow path in the Great Artesian Basin determined by 81Kr, 36Cl and 4He: Implications for palaeo hydrogeology.

Understanding the age distribution of groundwater can provide information on both the recharge history as well as the geochemical evolution of groundwater flow systems. Of the few candidates available that can be used to date old groundwater, 81Kr shows the most promise because its input function is constant through time and there are less sources and sinks to complicate the dating procedure in comparison to traditional tracers such as 36Cl and 4He. In this paper we use 81Kr in a large groundwater basin to obtain a better understanding of the residence time distribution of an unconfined-confined aquifer system. A suite of environmental tracers along a groundwater flow path in the south-west Great Artesian Basin of Australia have been sampled. All age tracers (85Kr, 39Ar 14C, 81Kr, 36Cl and 4He) display a consistent increase in groundwater age with distance from the recharge area indicating the presence of a connected flow path. Assuming that 81Kr is the most accurate dating technique the 36Cl/Cl systematics was unravelled to reveal information on recharge mechanism and chloride concentration at the time of recharge. Current-day recharge occurs via ephemeral river recharge beneath the Finke River, while diffuse recharge is minor in the young groundwaters. Towards the end of the transect the influence of ephemeral recharge is less while diffuse recharge and the initial chloride concentration at recharge were higher.

Optical excitation and decay dynamics of ytterbium atoms embedded in a solid neon matrix.

Neutral ytterbium atoms embedded in solid neon qualitatively retain the structure of free atoms. Despite the atom-solid interaction, the 6s6p ³P(0) level is found to remain metastable with its lifetimes determined to be in the range of ten to hundreds of seconds. The atomic population can be almost completely transferred between the ground level and the metastable level via optical excitation and spontaneous decay. The dynamics of this process is examined and is used to explicitly demonstrate that the transition broadening mechanism is homogeneous.

39Ar detection at the 10(-16) isotopic abundance level with atom trap trace analysis.

Atom trap trace analysis, a laser-based atom counting method, has been applied to analyze atmospheric 39Ar (half-life=269 yr), a cosmogenic isotope with an isotopic abundance of 8×10(-16). In addition to the superior selectivity demonstrated in this work, the counting rate and efficiency of atom trap trace analysis have been improved by 2 orders of magnitude over prior results. The significant applications of this new analytical capability lie in radioisotope dating of ice and water samples and in the development of dark matter detectors.

An electromagnetic separation system for the enrichment of 39Ar.

An isotope enrichment system for 39Ar has been developed at the Institute of Modern Physics, which is designed to increase the abundance of 39Ar in the incident sample gas. With intense Ar+ beams produced by a 2.45 GHz electron cyclotron resonance ion source and a high mass resolution spectrometer system, Ar isotopes are evidently separated on the target plane and selectively collected by an Al target. The separated Ar isotopes have been identified on the target plane, which is consistent with the simulations. According to the recent cross-checked results with atom trap trace analysis, a high enrichment factor of 39Ar has been successfully achieved. This paper will present the design and test results of this system.

Thermal beam of metastable krypton atoms produced by optical excitation.

A room-temperature beam of krypton atoms in the metastable 5s[3/2]2 level is demonstrated via an optical excitation method. A Kr-discharge lamp is used to produce vacuum ultraviolet photons at 124 nm for the first-step excitation from the ground level 4p6 1S0 to the 5s[3/2]1 level. An 819 nm Ti:sapphire laser is used for the second-step excitation from 5s[3/2]1 to 5s[3/2]2 followed by a spontaneous decay to the 5s[3/2]2 metastable level. A metastable atomic beam with an angular flux density of 3 x 10(14) s(-1) sr(-1) is achieved at the total gas flow rate of 0.01 cm3/s at STP (or 3 x 10(17) at./s). The dependences of the flux on the gas flow rate, laser power, and lamp parameters are investigated.

[Serum testosterone level of patients with cardiac or gastric carcinoma].

Serum testosterone level (STL) was examined in 25 male patients with cardiac or gastric carcinoma before and after operation and 28 male patients with benign diseases as control. The preoperative STL of patients with carcinoma was lower than that of the control (P less than 0.001). Postoperatively STL of these patients rose to the level of control group. When cancer recurred, STL again dropped to low level. STL was lower when cancer had invaded beyond the serosa than that limited to the musculature. Therefore, STL may be a good parameter for diagnosis and prognosis in patients with cancer of the stomach and gastric cardia.

[Significance of perioperative elevation of blood viscosity in patients with esophageal or cardiac carcinoma].

The blood viscosity of 21 patients with esophageal or cardiac carcinoma during preoperative period was measured and compared with that of 25 healthy persons. The results indicate that the blood viscosity in patients is higher than that in the control group (P < 0.001) immediately and one day after operation. Elevation of blood viscosity is not only related to myocardial infarction, but also may be one of the causes for the poor therapeutic effect in patients with carcinomas. It is suggested that proper measures should be taken to control the elevating blood viscosity in patients, especially the elderly ones during the perioperative period. Colloid fluid which is believed to increase blood viscosity should be avoided within the first two days after operation to prevent cardiac complications.

[Sharing antigenic determinant of colon carcinoma between serous and mucinous tumors of the ovary].

Expression of colon-ovarian tumor antigen (COTA) in serous and mucinous tumors of the ovary was determined immunohistochemically, using monoclonal antibody SC13A against colon carcinoma antigen as a probe. In 67 serous tumor of the ovary, the frequency of expression was 90.0% in the cystadenocarcinomas, 71.4% in the borderline cystadenomas, and only 8.0% in the cystadenomas. In 44 mucinous tumors of the ovary, the SC13A marker was expressed in 87.5% of the malignant tumors, 80.0% of the borderline tumors, and 25.8% of the benign cystadenomas. And in 20 samples of normal ovarian tissue a negative immunostaining for the SC13A was found. These findings showed that the serous and the mucinous tumors share the same antigenic determinant of colon cancer, and the percentage expression of which is significantly higher in the malignant than in the benign and the borderline tumors, as well as in the normal ovarian tissues (P < 0.005). The marker might be valuable for further studies of these tumors.

[Serum testosterone level in patients with cardiac or gastric carcinoma before and after surgery].

Serum testosterone level (STL) was determined in 52 male patients with cardiac carcinoma and in 48 male patients with gastric carcinoma before and after operation, and in 54 normal male subjects and preoperative 40 male patients with benign diseases as control groups. The STL of the patients with cardiac carcinoma or gastric carcinoma was lower than the normal group and the benign diseases group (P less than 0.001, respectively). The postoperative STL of the patients with cardiac or gastric carcinoma was not significantly different from the normal group and the benign diseases group. The STL was lower in patients with recurrence than in the normal group and benign diseases group (P less than 0.001, respectively), and lower in patients with cardiac or gastric carcinoma invading outside the serosa than in those with lesions confined to the musculature (P less than 0.001 and P less than 0.05). Therefore, it appears that the STL may be an important parameter in diagnosis, and in the evaluation of prognosis, postoperative recurrence and resectability of the tumors.

[Thoracic gastric and large area necrotic perforation of the neck gastric wall after surgery of esophageal and cardial cancer: analysis of 9 cases].

Nine cases of gastric perforation after operation for esophageal were reported. Eight cases were esophageal cancer. One case was cardial cancer. Five of the nine cases were anastomosed in intrathorax, and four in neck. Intrathoracic gastric perforation occurred in six cases. Five of them were operated on again. Gastric perforation in neck occurred in three cases. The nine cases were all cured. This article analysed the reasons of the gastric perforation and emphasised that early diagnosis, early operation or drainage in neck were the key steps in treatment.

Note: efficient generation of optical sidebands at GHz with a high-power tapered amplifier.

Two methods using a laser-diode tapered amplifier to produce high-power, high-efficiency optical frequency sidebands over a wide tunable frequency range are studied and compared. For a total output of 500 mW at 811 nm, 20% of the power can be placed in each of the first-order sidebands. Functionality and characterization are presented within the sideband frequency region of 0.8-2.3 GHz, and it is shown that both methods can be applied beyond this frequency range. These methods provide a versatile and effective tool for atomic physics experiments.

Analysis of 85Kr: a comparison at the 10 -14 level using micro-liter samples.

The isotopic abundance of (85)Kr in the atmosphere, currently at the level of 10(-11), has increased by orders of magnitude since the dawn of nuclear age. With a half-life of 10.76 years, (85)Kr is of great interest as tracers for environmental samples such as air, groundwater and ice. Atom Trap Trace Analysis (ATTA) is an emerging method for the analysis of rare krypton isotopes at isotopic abundance levels as low as 10(-14) using krypton gas samples of a few micro-liters. Both the reliability and reproducibility of the method are examined in the present study by an inter-comparison among different instruments. The (85)Kr/Kr ratios of 12 samples, in the range of 10(-13) to 10(-10), are measured independently in three laboratories: a low-level counting laboratory in Bern, Switzerland, and two ATTA laboratories, one in Hefei, China, and another in Argonne, USA. The results are in agreement at the precision level of 5%.