A super-high resolution frequency standard measuring approach based on phase coincidence characteristics between signals

A method for super high resolution comparison measurement is proposed in this paper with a comparison between the frequency standards of different nominal frequencies, which is based on phase coincidence detection of the two compared signals. It utilizes the regular phase shift characteristics between the signals. The resolution of the measurement approach can reach 10-13/s at 5 MHz, and the self-calibration resolution can achieve 10-14/s in the comparison between 10 MHz and 100 MHz, or even can reach 10-15/s in the comparison between 10 MHz and 190 MHz. This method implies significant progress in the development of the high precision frequency standard comparison technology.     

Diode-laser spectroscopy of supersonic free jets

A supersonic-free-jet infrared spectrometer has been constructed for investigation of molecular vibrational spectra at low rotational and vibrational temperatures. The sensitivity of measurement in a pulsed jet is increased by employing a phase-sensitive detection method synchronized with the pulse frequency. The performance of the spectrometer is examined for the absorption lines of the NH₃ v ₂ band. A rotational temperature as low as 16K is attained when seeded in He. Cold-jet spectra are demonstrated for thev ₃ bands of PF₅,³⁴SF₆, and¹⁸²WF₆.     

非消声水池中低频换能器测量的空间域处理方法

提出了一种在非消声水池中低频换能器测量的空间域处理方法。该方法是在发射和接收换能器保持相对位置不变的情况下,通过多次无规则变换其在有限水域中的位置,让同频反射声的干扰贡献随机和无规则化,最终将上述所有位置接收的信号同步叠加而将同频反射声干扰消除,从而提取出了所需的直达波波形信号,克服了传统的脉冲测量技术受同频反射声干扰无法提取直达信号的问题。在5 m×7 m×6 m非消声水池,测量换能器样品,测量频率范围是400~2500 Hz,测量得到的结果与湖上测试结果相比,两者基本一致。该方法的实现,大大的提高了非消声水池的低频换能器测试能力,有效测量频率下限比一般脉冲测试方法降低一个数量级。      

Observations of stark broadening of resonance lines in a beryllium,laser produced plasma

The resonance lines of Be IV are Stark-broadened in a laser produced plasma. The distribution of the electron density is derived by a measurement of the line profiles and comparison with theory. Density values up to 10²¹ cm^-3 have been found near the target.     

High multipolarity electroexcitations in 207Pb and 206Pb

We report the identification of new high multipolarity transitions in ²⁰⁷Pb and ²⁰⁶Pb by the measurement of their form factor. A comparison to the corresponding excitations in ²⁰⁸Pb is presented.     

Neutron capture gamma-rays from the low-lying resonances of 54Fe

Neutron capture γ-rays have been observed from the low-lying resonances of ⁵⁴Fe using the Harwell electron linear accelerator HELIOS as a neutron source. Relative values for the partial radiative widths of resolved lines were obtained by area analysis of the γ-rays peaks over neutron resonance regions, and absolute values were obtained by a shape analysis fit to the yield deduced by comparison with a ¹⁰B(n, αγ)⁷Li measurement. For the 7.8 keV s-wave resonance, a comparison of the partial widths with the predictions of the valence model has been made. In both relative and absolute senses, there is good agreement.     

Beta decay of 103In: Evidence for the Gamow-Teller resonance near 100Sn

The β decay of the neutron-deficient isotope ¹⁰³In was investigated by using total absorption γ-ray spectrometry on mass-separated sources. The measurement reveals a high-lying resonance of the β-decay strength in striking disagreement with high-resolution γ-ray data. The result is discussed in comparison with shell-model predictions.     

Knockout of proton-neutron pairs from 16O with electromagnetic probes

After recent improvements to the Pavia model of two-nucleon knockout from ¹⁶O with electromagnetic probes the calculated cross-sections are compared to experimental data from such reactions. Comparison with data from a measurement of the ¹⁶O (e,e’ pn) reaction cross-section shows much better agreement between the experimental data and the results of the theoretical model than was previously observed. In a comparison with recent data from a measurement of the ¹⁶O ( $ \gamma$ ,pn) reaction cross-section the model over-predicts the measured cross-section at low missing momentum.     

Low-lying states and degree of chaoticity of40K in IBFFM

The results of aγ-γ angular correlation and a low energyγ-ray singles measurement using thermal neutron capture in³⁹K are presented. The properties of low-lying levels of⁴⁰K are interpreted in a comparison of the experimental data with the Interacting-Boson-Fermion-Fermion Model (IBFFM). The level fluctuation properties of the IBFFM spectrum are analysed and a sizeable deviation from chaoticity is found.     

Spectroscopy of the hyperfine structure of antiprotonic 4He and 3He

The spin magnetic moment $\mu^{\overline{p}}_{s}$ of the antiproton can be determined by comparing the measured transition frequencies in $\overline{p}^4$ He^?+? with three-body QED calculations. A comparison between the proton and antiproton can then be used as a test of CPT invariance. The highest measurement precision of the difference between the proton and the antiproton spin magnetic moments to date is 0.3%. A new experimental value of the spin magnetic moment of the antiproton was obtained as $\mu^{\overline{p}}_{s} = -2.7862(83)\mu_{N}$ , slightly better than the previously best measurement. This agrees with $\mu^{p}_{s}$ within 0.24%. In 2009, a new measurement with antiprotonic ³He has been started. A comparison between the theoretical calculations and experimental results would lead to a stronger test of the theory and address systematic errors therein. A measurement of this state will be the first HF measurement on $\overline{p}^3$ He^?+?. We report here on the new experimental setup and the first tests.     

Evaluation of the magnetic moments of radium isotopes

Using the relativistic linked cluster many-body perturbation procedure we have obtained the hyperfine field at the nucleus of the Ra⁺ ion in the²S_1/2 ground state. There is good agreement between the calculated magnetic moment of²¹³Ra and the results of a recent Zeeman measurement by the collinear laser beam technique. Detailed comparison is carried out between our result and earlier ones.     

Isotopic composition and concentration measurements of atmospheric CO2 with a diode laser making use of correlations between non-equivalent absorption cells

Correlations between a sample and a sealed reference cell of a tunable diode laser spectrometer for the measurement of the isotopic composition (δ ¹³C) and the concentration of atmospheric carbon dioxide in air have been investigated. Likely due to fluctuations of the laser emission profile, these correlations have been used to improve the performance of the instrument. In a comparison with isotope ratio mass spectrometer and gas chromatographic measurements, an accuracy of 0.15‰ for δ ¹³C and 0.05 ppmv for the CO₂ concentration is demonstrated for 40 s integration time. Long-term stability and field deployment of the instrument have been investigated during a few days measurement campaign in Paris.     

Calculation of the electrodisintegration cross section of4He

In the framework of a previously discussed translationally invariant particle hole model theT=1 part of the differential electrodisintegration cross section of⁴He is calculated. A comparison with a recent measurement of this reaction gives fairly quantitative agreement, but it is suggested that in the region below 26 MeV excitation energy besides the 2^? T=1 state the 2^? T=0 state presumably gives an appreciable contribution to the cross section thus indicating that the usually observed isospin selection rule does not work in this case.     

A cluster algorithm for jet studies

A procedure is described which determines the number of jets in hadronic final states by means of a cluster algorithm. In addition it yields a measurement of the energy and the direction of each jet. The properties of this method are studied using Monte Carlo simulations of different types ofe ⁺ e ^?-annihilation final states. It is shown that in the case of 3-jet events direct comparison with the underlying parton structure can be made. Possible further applications of this method are discussed.     

Optical–feedback cavity–enhanced absorption: a compact spectrometer for real–time measurement of atmospheric methane

We report on the application of the new technique of optical–feedback cavity–enhanced absorption spectroscopy to the real–time quantitative measurement of tropospheric methane traces from an airplane using a compact, low cost instrument based on a telecommunication–type diode laser operating close to room temperature. Methane concentration is obtained by fitting the absorption line centered at 1658.96 nm (6026.23 cm^-1) which belongs to the first overtone transition of the CH stretch vibration. The measurement rate is about 30 Hz, but the response time is limited to about 0.3 s by the gas flow in the measurement cell. The instrument provides the absolute ambient methane concentration accurate to ±1% (±20 ppb) without need for a periodic calibration. This is demonstrated by a hands–off comparison with a self–calibrating chromatographic setup during 10 days. The observed measurement stability can be extrapolated to much longer time periods. With respect to the short–term performance (minutes) fast concentration changes at the level of 1 ppb can be detected, and we believe this performance can be extended to the long term. Finally, a laboratory comparison with a lead–salt mid–infrared diode laser multipass spectrometer (operating close to 3028 cm^-1 at liquid nitrogen temperature) demonstrates a similar performance. PACS 07.88.+y; 42.55.Px; 42.62.Fi     

Multiplexing photons with a binary division strategy

We present a scheme to produce clock-synchronized photons from a single parametric downconversion source with a binary division strategy. The time difference between a clock and detections of the herald photons determines the amount of delay that must be imposed to a photon by actively switching different temporal segments, so that all photons emerge from the output with their wavepackets temporally synchronized with the temporal reference. The operation is performed using a binary division configuration which minimizes the passages through switches. Finally, we extend this scheme to the production of many synchronized photons and find expressions for the optimal amount of correction stages as a function of the pair generation rate and the target coherence time. Our results show that, for the generation of this heralded single-photon per output state at an optimized input photon flux, the output rate of our scheme scales essentially with the reciprocal of the target output photon number. With current technology, rates of up to 10⁴ synchronized pairs per second could be observed with only 7 correction stages.     

Angle- and spin-resolved photoelectron spectroscopy of the Hg 5d 10 subshell

Parameters describing electron spin polarization in Hg 5d ¹⁰ subshell photoionization have been measured at rare-gas resonance wavelengths between 73.59 nm and 30.38 nm. The spin parameters as well as asymmetry parameters β of a recent measurement are discussed in comparison with both nonrelativistic and relativistic ab initio calculations of several authors. The importance of many-electron correlations and spin-orbit coupling effects is considered.     

Magnetic Screening of 19F Nuclei in Perovskite KMgF3

The present work cites the measurement data for the magnetic screening tensor of fluorine nuclei in KMgF₃ and comparison results of ¹⁹F screening tensor components in this substance with the theoretical, based on the overlapping pattern of ion wave functions.     

On the intensities ofK X rays following thermal neutron capture

Through the measurement of the absolute intensities of theK _α andK _β X rays following slow neutron capture in¹⁵⁵Gd,¹⁷⁶Lu and¹⁹⁹Hg and their comparison with the intensities of theK-conversion electron transitions from the same reaction it is shown that theK X rays are caused only by internal conversion.     

Comparative analysis of cross sections of residual nuclei on separated tin isotopes at a beam energy of protons and deuterons 3.65 GeV/nucleon

The cross sections of residual nuclei in the separated tin isotopes (¹¹²Sn, ¹¹⁸Sn, ¹²⁰Sn, and ¹²⁴Sn), irradiated with proton and deuteron beams with energy 3.65 GeV/nucleon, are investigated. Parametrization by ten parametric semi-empirical formula was conducted with the aim of determining the total cross sections and analyzing the measurement results. The dependence of total inelastic cross sections on the mass number of the target and the structure of the incoming particle was investigated via the comparison of the obtained data.