Numerical simulation of flow in Hartmann resonance tube and flow in ultrasonic gas atomizer

The gas flow in the Hartmann resonance tube is numerically investigated by the finite volume method based on the Roe solver. The oscillation of the flow is studied with the presence of a needle actuator set along the nozzle axis. Numerical results agree well with the theoretical and experimental results available. Numerical results indicate that the resonance mode of the resonance tube will switch by means of removing or adding the actuator. The gas flow in the ultrasonic gas atomization （USGA） nozzle is also studied by the same numerical methods. Oscillation caused by the Hartmann resonance tube structure, coupled with a secondary resonator, in the USGA nozzle is investigated. Effects of the variation of parameters on the oscillation are studied. The mechanism of the transition of subsonic flow to supersonic flow in the USGA nozzle is also discussed based on numerical results.

Fast thermometry for trapped atoms using recoil-induced resonance

We have employed recoil-induced resonance（RIR） with linewidth on the order of 10 k Hz to demonstrate the fast thermometry for ultracold atoms. We theoretically calculate the absorption spectrum of RIR which agrees well with the experimental results. The temperature of the ultracold sample derived from the RIR spectrum is T = 84 ± 4.5 μK, which is close to 85 μK that measured by the method of time-of-flight absorption imaging. To exhibit the fast measurement advantage in applying RIR to the ultracold atom thermometry, we study the dependence of ultracold sample temperature on the trapping beam frequency detuning. This method can be applied to determine the translational temperature of molecules in photoassociation dynamics.

Electric-field-modified Feshbach resonances in ultracold atom–molecule collision

We present a detailed analysis of near zero-energy Feshbach resonances in ultracold collisions of atom and molecule,taking the He–PH system as an example, subject to superimposed electric and magnetic static fields. We find that the electric field can induce Feshbach resonance which cannot occur when only a magnetic field is applied, through couplings of the adjacent rotational states of different parities. We show that the electric field can shift the position of the magnetic Feshbach resonance, and change the amplitude of resonance significantly. Finally, we demonstrate that, for narrow magnetic Feshbach resonance as in most cases of ultracold atom–molecule collision, the electric field may be used to modulate the resonance, because the width of resonance in electric field scale is relatively larger than that in magnetic field scale.

Experimental Study on Double Resonance Optical Pumping Spectroscopy in a Ladder-Type System of ^(87)Rb Atoms

Double resonance optical pumping spectroscopy has an outstanding advantage of high signal-to-noise ratio, thus having potential applications in precision measurement. With the counter propagated 780nm and 776nm laser beams acting on a rubidium vapor cell, the high resolution spectrum of 5S1/2 - 5P3/2 - 5D5/2 ladder-type transition of ST Rb atoms is obtained by monitoring the population of the 5S1/2 ground state. The dependence of the spectroscopy lineshape on the probe and coupling fields are comprehensively studied in theory and experiment. This research is helpful for measurement of fundamental physical constants by high resolution spectroscopy.

The Hydrogen Atom Fundamental Resonance States

In the 1920’s, Louis de Broglie’s observation that the integer sequence that could be related to the interference patterns produced by the various electromagnetic energy quanta emitted by hydrogen atoms was identical to those of very well known classical resonance processes, made him conclude that electrons were captive in resonance states within atoms. This led Schrädinger to propose a wave function to represent these resonance states that still have not been reconciled with the electromagnetic properties of electrons. This article is meant to identify and discuss the electromagnetic harmonic oscillation properties that the electron must possess as a resonator in order to explain the resonance volume described by the wave function, as well as the electromagnetic interactions between the elementary charged particles making up atomic structures that could explain electronic and nucleonic orbitals stability. An unexpected benefit of the expanded space geometry required to establish these properties and interactions is that the fundamental symmetry requirement is respected by structure for all aspects of the distribution of energy within electromagnetic quanta.

Unnatural parity resonance states in positron-excited hydrogen scattering

The coupled-channels optical method for positron scattering has been applied to investigate resonance states with unnatural parities in a positron-excited hydrogen system. The positronium formation channels and continuum channel are included via a complex equivalent local potential. Resonance states with angular momenta L =- 1 to L = 2 and parities （-1）L＋1 are calculated. Resonance energies and widths are reported and compared with other theoretical calculations. We found that the opening positronium formation channels play an important role in forming nondipole Feshbach resonances.

Combined effect of light intensity and temperature on the magnetic resonance linewidth in alkali vapor cell with buffer gas

One of the peculiar phenomenons in non-zero magnetic resonance magnetometer is that, with the increase of the temperature, the magnetic resonance linewidth is narrowed at first instead of broadened due to the increasing collision rate. The magnetometer usually operates at the narrowest linewidth temperature to obtain the best sensitivity. Here, we explain this phenomenon quantitatively considering the nonlinear of the optical pumping in the cell and did experiments to verify this explanation. The magnetic resonance linewidth is measured using one amplitude-modulated pump laser and one continuous probe laser. The field is along the direction orthogonal to the plane of pump and probe beams. We change the temperature from 53℃ to 93℃ and the pumping light from 0.1 mW to 2 mW. The experimental results agree well with the theoretical calculations.

Spin dynamics of magnetic resonance with parametric modulation in a potassium vapor cell

A typical magnetic-resonance scheme employs a static bias magnetic field and an orthogonal driving magnetic field oscillating at the Larmor frequency, at which the atomic polarization precesses around the static magnetic field. Here we demonstrate both theoretically and experimentally the variations of the resonance condition and the spin precession dynamics resulting from the parametric modulation of the bias field. We show that the driving magnetic field with the frequency detuned by different harmonics of the parametric modulation frequency can lead to resonance as well. Also, a series of frequency sidebands centered at the driving frequency and spaced by the parametric modulation frequency can be observed in the precession of the atomic polarization. We further show that the resonant amplitudes of the sidebands can be controlled by varying the ratio between the amplitude and the frequency of the parametric modulation. These effects could be used in different atomic magnetometry applications.

Properties of acoustic resonance in double-actuator ultra-sonic gas nozzle:numerical study

The ultra-sonic gas atomization （USGA） nozzle is an important apparatus in the metal liquid air-blast atomization process. It can generate oscillating supersonic gas effiux, which is proved to be effective to enforce the atomization and produce narrow-band particle distributions. A double-actuator ultra-sonic gas nozzle is proposed in the present paper by joining up two active signals at the ends of the resonance tubes. Numerical sim- ulations axe adopted to study the effects of the flow development on the acoustic resonant properties inside the Haxtmann resonance cavity with/without actuators. Comparisons show that the strength and the onset process of oscillation are enhanced remarkably with the actuators. The multiple oscillating amplitude peaks are found on the response curves, and two kinds of typical behaviors, i.e., the Hartmann mode and the global mode, are discussed for the corresponding frequencies. The results for two driving actuators are also investigated. When the amplitudes, the frequencies, or the phase difference of the input signals of the actuators are changed, the oscillating amplitudes of gas effiux can be altered effectively.

Coherent Resonance of Saturated Absorption in Spectroscopy of Counterpropagating Waves

Results of theoretical researches of the saturated absorption resonance shape in a method of the probing field on V-type of transitions are represented. It is shown that in case of opposite circulary polarized optical fields the resonance is shown in the form of cross, and its form strongly depends on relaxation constants of levels and it can be represented as in the form of a dip, and absorption peak. Thus the peak form has exclusively coherent character. Atomic transitions are offered, on which observation of the given effect is possible.

Widely tunable laser frequency offset locking to the atomic resonance line with frequency modulation spectroscopy

A simple and robust technique is reported to offset lock a single semiconductor laser to the atom resonance line with a frequency difference easily adjustable from a few tens of megahertz up to tens of gigahertz. The proposed scheme makes use of the frequency modulation spectroscopy by modulating sidebands of a fiber electro-optic modulator output. The short-term performances of a frequency offset locked semiconductor laser are experimentally demonstrated with the Allan variance of around 3.9 × 10-11 at a 2 s integration time. This method may have many applications, such as in Raman optics for an atom interferometer.

An atomic electronegative distance vector and carbon-13 nuclear magnetic resonance chemical shifts of alcohols and alkanes

A novel atomic electronegative distance vector (AEDV) has been developed to express the chemical environment of various chemically equivalent carbon atoms in alcohols and alkanes. Combining AEDV and γ parameter, four five-parameter linear relationship equations of chemical shift for four types of carbon atom are created by using multiple linear regression. Correlation coefficients are R = 0.9887, 0.9972, 0.9918 and 0.9968 end roots of mean square error are RMS = 0.906, 0. 821, 1.091 and 1.091 of four types of carbons, i.e., type 1, 2, 3, and 4 for primary, secondary, tertiary, and quaternary carbons, respectively. The stability and prediction capacity for external samples of four models have been tested by cross-validation.

Application of coupled equation method on resonance processes of atomic lithium

The coupled equation method （CEM） has been applied to investigating the resonance structures for the ground state 1s^22s^ 2S of the neutral lithium from the first threshold up to 64.5 eV. Resonance structures of atomic lithium due to single excitations of the ls and 2s electrons are studied by infinite-order calculations in detail. The effect of spin-orbit splitting is also included for some of the low-lying ls2snp（↑↓） resonance, and the influence of the interference between 1s^2s^3 Snp .↓ and 1s2s^ 1 Snp ↑ states on the resonance structure has been confirmed theoretically. The results show that the presented technique can give the reasonable resonance structures very well in photoionization processes.

Investigation of carbon-13 nuclear magnetic resonance spectra-structure correlation based on novel atomic distance-edge (ADE) vector

A set of novel graph-theoretical parameters, called the atomic distance-edge (ADE) vector, was developed. Baaed on the connecting C-C bond number between central carbon atom and the other ones, various carbon atoms of alkanes were classified as four types, i.e., type 1, 2, 3 and 4 for primary, secondary, ternary and quaternary carbon, respectively; and then four regression equations were obtained to link carbon-13 chemical shift (CS) of each type of atoms. Furthermore, these regression models were used to predict the carbon-13 nuclear magnetic resonance spectra of alkanes and it was found that the estimated CS were in agreement with the experimental results.

Single atoms transferring between a magneto-optical trap and a far-off-resonance optical dipole trap

Based on our work on single cesium atoms trapped in a large-magnetic-gradient vapour-cell magneto-optical trap （MOT）, the signal-to-noise ratio （SNR） is remarkably improved. Also a far-off-resonance optical dipole trap （FORT） formed by a strongly-focused 1064 nm single frequency Nd：YVO4 laser beam is introduced. One cesium atom is prepared in the MOT, and then it can transfer successfully between the MOT and the FORT which is overlapped with the MOT. Utilizing the effective transfer, the lifetime of single atoms trapped in the FORT is measured to be 6.9± 0.3 s. Thus we provide a system where the atomic qubit can be coherently manipulated.

Observation of High-lying Odd Levels of Uranium Atom in Two-colour Three-photon Resonant Photoionization Spectrum

1 Introduction Thousands of energy levels of uranium atom are being found, but it is difficult to identify and assign them because of the complicatedness of UI spectrum. Most of the information about the uranium atom energy levels was obtained from the analysis of the emission or absorption spectra got in conventional sources, such as hollow cathode or electrodeless discharge lamps. As higher excited states are thinly populated in these conventional sources, most of the data available in literature pertain to low and medium

OBSERVATION ON SINGLE-COLOUR THREEPHOTON IONIZATION SPECTROSCOPY OF URANIUM ATOM

Ⅰ. INTRODUCTION Since the ionizing potential of uranium is 49958 cm-1, at least three photons of wavelengths in visible region are required to ionize an uranium atom from its ground state or one of the low-lying metastable states. When a single-colour laser beam acts with the uranium vapor, the uranium atom can sequentially absorb three photons and ionize, but the cross sec-

Resonances of a hydrogen atom in strong parallel electric and magnetic fields using B-spline basis sets

The B-spline basis set plus complex scaling method is applied to the numerical calculation of the exact resonance parameters Er and Г/2 of a hydrogen atom in parallel electric and magnetic fields. The method can calculate the ground and higher excited resonances accurately and efficiently. The resonance parameters with accuracies of 10^-9 - 10^-12 for hydrogen atom in parallel fields with different field strengths and symmetries are presented and compared with previous ones. Extension to the calculation of Rydberg atom in crossed electric and magnetic fields and of atomic double excited states in external electric fields is discussed.

Scattering resonances between ultracold atoms and molecules observed for the first time

With the support by the National Natural Science Foundation of China,the National Key R&-D Program of China,and the Chinese Academy of Sciences,the research team led by Prof.Pan JianWci(潘建伟)and Prof.Zhao Bo(赵博)at the University of Science and Technology of China have successfully observed scattering resonances between atoms and molecules at ultralow temperatures,shedding light on the quantum nature of atom-molecule interactions.This work was published in Science(2019,363:261--264).

Quantitative measurement of local elasticity of SiO_x film by atomic force acoustic microscopy

In this paper the elastic properties of SiOx film are investigated quantitatively for local fixed point and qualitatively for overall area by atomic force acoustic microscopy （AFAM） in which the sample is vibrated at the ultrasonic frequency while the sample surface is touched and scanned with the tip contacting the sample respectively for fixed point and continuous measurements. The SiOx films on the silicon wafers are prepared by the plasma enhanced chemical vapour deposition （PECVD）, The local contact stiffness of the tip-SiOx film is calculated from the contact resonance spectrum measured with the atomic force acoustic microscopy. Using the reference approach, indentation modulus of SiOx film for fixed point is obtained. The images of cantilever amplitude are also visualized and analysed when the SiOx surface is excited at a fixed frequency. The results show that the acoustic amplitude images can reflect the elastic properties of the sample.