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<jats:p>The nickel-base alloy is one of the leading candidate materials for generation IV nuclear reactor pressure vessel. To evaluate its stability of helium damage and retention, helium ions with different energy of 80 keV and 180 keV were introduced by ion implantation to a certain dose (peak displacement damage 1–10 dpa). Then thermal desorption spectroscopy (TDS) of helium atoms was performed to discuss the helium desorption characteristic and trapping sites. The desorption peaks shift to a lower temperature with increasing dpa for both 80 keV and 180 keV irradiation, reflecting the reduced diffusion activation energy and faster diffusion within the alloy. The main release peak temperature of 180 keV helium injection is relatively higher than that of 80 keV at the same influence, which is because the irradiation damage of 180 keV, helium formation and entrapment occur deeper. The broadening of the spectra corresponds to different helium trapping sites (He–vacancies, grain boundary) and desorption mechanisms (different He<jats:sub> <jats:italic>n</jats:italic> </jats:sub>V<jats:sub> <jats:italic>m</jats:italic> </jats:sub> size). The helium retention amount of 80 keV is lower than that of 180 keV, and a saturation limit associated with the irradiation of 80 keV has been reached. The relatively low helium retention proves the better resistance to helium bubbles formation and helium brittleness.</jats:p>

<jats:p>Accurate non-Born–Oppenheimer variational calculations of all bound states of the positive muon molecular ion <jats:sup>4</jats:sup>Heμ<jats:sup>+</jats:sup> have been performed using explicitly correlated Gaussian functions in conjunction with the global vectors. All the energies obtained are accurate in the order of 10<jats:sup>−6</jats:sup> Hartree (1 Hartree = 27.2114 eV). Compared with the binding energies obtained from calculations based on the Born–Oppenheimer potential with the mass-weighted adiabatic corrections (<jats:italic>Chem. Phys. Lett.</jats:italic> <jats:bold>110</jats:bold> 487 (1984)), the largest relative deviation is up to 15%. By analyzing the average interparticle distances and possibility distributions of interparticle distances of this system, it is confirmed that the Born–Oppenheimer approximation is reasonable for this system and that <jats:sup>4He</jats:sup> μ<jats:sup>+</jats:sup> can be regarded as a system of positive muon bound to a slightly distorted helium atom.</jats:p>

<jats:p>The phase partition and site preference of Re atoms in a ternary Ni–Al–Re model alloy, including the electronic structure of different Re configurations, are investigated with first-principles calculations and atom probe tomography. The Re distribution of single, nearest neighbor (NN), next-nearest neighbor (NNN), and cluster configurations are respectively designed in the models with <jats:italic>γ</jats:italic> and <jats:italic>γ</jats:italic>′ phases. The results show that the Re atoms tend to entering <jats:italic>γ</jats:italic>′ phase and the Re atoms prefer to occupy the Al sites in <jats:italic>γ</jats:italic>′ phase. The Re cluster with a combination of NN and NNN Re–Re pair configuration is not preferred than the isolated Re atom in the Ni-based superalloys, and the configuration with isolated Re atom is more preferred in the system. Especially, the electronic states are analyzed and the energetic parameters are calculated. The electronic structure analyses show there exists strong Ni–Re electronic interaction and it is mainly contributed by the d–d hybridization. The characteristic features of the electronic states of the Re doping effects are also given. It is also found that Re atoms prefer the Al sites in <jats:italic>γ</jats:italic>′ side at the interface. The density of states at or near the Fermi level and the d–d hybridizations of NN Ni–Re are found to be important in the systems.</jats:p>

<jats:p>Controlling paths of high-order harmonic generation from <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{H}}}_{2}^{+}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">H</mml:mi> <mml:mn>2</mml:mn> <mml:mo>+</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_29_4_043201_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> is theoretically investigated by numerically solving the time-dependent Schrödinger equation based on the Born–Oppenheimer approximation in orthogonal two-color fields. Our simulations show that the change of harmonic emission paths is dependent on time-dependent distribution of electrons. Compared with one-dimensional linearly polarized long wavelength laser, multiple returns are suppressed and short paths are dominant in the process of harmonic emission by two-dimensional orthogonal <jats:italic>ω</jats:italic>/2<jats:italic>ω</jats:italic> laser fields. Furthermore, not only are multiple returns weaken, but also the harmonic emission varies from twice to once in an optical cycle by orthogonal <jats:italic>ω</jats:italic>/1.5<jats:italic>ω</jats:italic> laser fields. Combining the time–frequency distributions and the time-dependent electron wave packets probability density, the mechanism of controlling paths is further explained. As a result, a 68-as isolated attosecond pulse is obtained by superposing a proper range of the harmonics.</jats:p>

<jats:p>Electron collision as well as its controlling lies in the core of study on nonsequential double ionization (NSDI). A single collision occurred in a convergent time is important to disclose the essential features of the electron correlation. However, it is difficult to form such a collision. By using counterrotating circular two-color (CRTC) laser fields, we show that a single electron collision can be achieved in a convergent time and a net electron correlation is set up within the sub-femtosecond time scale in the NSDI process of Ar atoms. The proposed method is also valid for other atoms, provided that one chooses the frequency and intensity of the CRTC field according to a scaling law.</jats:p>

<jats:p>We demonstrate the generation of the coherent 420 nm laser via parametric four-wave mixing process in Rb vapor. A single 778 nm laser with circular polarization is directly injected into a high-density atomic vapor, which drives the atoms from the 5S<jats:sub>1/2</jats:sub> state to the 5D<jats:sub>5/2</jats:sub> state with monochromatic two-photon transition. The frequency up-conversion laser is generated by the parametric four-wave mixing process under the phase matching condition. This coherent laser is firstly certified by the knife-edge method and a narrow range grating spectrometer. Then the generated laser power is investigated in terms of the power and frequency of the incoming beam as well as the density of the atoms. Finally, a 420 nm coherent laser with power of 19 μW and beam quality of <jats:inline-formula> <jats:tex-math><?CDATA ${M}_{x}^{2}=1.32$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>M</mml:mi> <mml:mi>x</mml:mi> <mml:mn>2</mml:mn> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>1.32</mml:mn> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_29_4_043203_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math><?CDATA ${M}_{y}^{2}=1.37$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>M</mml:mi> <mml:mi>y</mml:mi> <mml:mn>2</mml:mn> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>1.37</mml:mn> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_29_4_043203_ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> is obtained with optimal experimental parameters. This novel laser shows potential prospects in the measurement of material properties, information storage, and underwater optical communication.</jats:p>

<jats:p>The total effective spin-exchange relaxation of naturally abundant Rb in a K–Rb–<jats:sup>21</jats:sup>Ne comagnetometer is analyzed, and the results show that the coexistence of <jats:sup>87</jats:sup>Rb and <jats:sup>85</jats:sup>Rb isotopes in the same volume can lead to a large extra spin-exchange broadening compared to pure <jats:sup>87</jats:sup>Rb. This broadening mainly comes from the contribution of the equivalent reduction in the Rb spin-exchange rate. On this basis, an approximate relaxation model is proposed and experimentally demonstrated to be more accurate than that from a previous work. This study also provides a method for determining the properties of alkali-metal vapor cells.</jats:p>

<jats:p>Bauer recently presented a formula for the ionization rate of a hydrogen atom in a strong linearly polarized laser field [<jats:italic>J. Phys. B</jats:italic> <jats:bold>49</jats:bold> 145601 (2016)]. He started from the Keldysh probability amplitude in the length gauge and utilized Reiss’s method in the velocity gauge. Instead, according to the Reiss probability amplitude in the velocity gauge and Keldysh’s derivation for the length gauge, we derive a formula for the ionization rate of a ground-state hydrogen atom or a hydrogen-like atom in a strong linearly polarized laser field. We compare the numerical results of the total ionization rate and the photoelectron energy distribution calculated from our formula with the results from Keldysh, Reiss, and Bauer. We find that the apparent discrepancies in the ionization rate are caused not only by different gauges, but also by different analytical methods used to derive the ionization rate.</jats:p>

<jats:p>The hybrid optical pumping spin exchange relaxation free (HOPSERF) atomic co-magnetometers make ultrahigh sensitivity measurement of inertia achievable. The wall relaxation rate has a big effect on the polarization and fundamental sensitivity for the co-magnetometer, but it is often neglected in the experiments. However, there is almost no work about the systematic analysis of the influence factors on the polarization and the fundamental sensitivity of the HOPSERF co-magnetometers. Here we systematically study the polarization and the fundamental sensitivity of <jats:sup>39</jats:sup>K–<jats:sup>85</jats:sup>Rb–<jats:sup>21</jats:sup>Ne and <jats:sup>133</jats:sup>Cs–<jats:sup>85</jats:sup>Rb–<jats:sup>21</jats:sup>Ne HOPSERF co-magnetometers with low polarization limit and the wall relaxation rate. The <jats:sup>21</jats:sup>Ne number density, the power density and wavelength of pump beam will affect the polarization greatly by affecting the pumping rate of the pump beam. We obtain a general formula on the fundamental sensitivity of the HOPSERF co-magnetometers due to shot-noise and the fundamental sensitivity changes with multiple systemic parameters, where the suitable number density of buffer gas and quench gas make the fundamental sensitivity highest. The fundamental sensitivity 7.5355×10<jats:sup>–11</jats:sup> rad·s<jats:sup>–1</jats:sup>·Hz<jats:sup>–1/2</jats:sup> of <jats:sup>133</jats:sup>Cs–<jats:sup>85</jats:sup>Rb–<jats:sup>21</jats:sup>Ne co-magnetometer is higher than the ultimate theoretical sensitivity 2×10<jats:sup>–10</jats:sup> rad·s<jats:sup>–1</jats:sup>·Hz<jats:sup>–1/2</jats:sup> of K–<jats:sup>21</jats:sup>Ne co-magnetometer.</jats:p>

<jats:p>We study the influence of driving ways on the interaction in a two-atoms cavity quantum electrodynamics system. The results show that driving ways can induce different excitation pathways. We show two kinds of significantly different excitation spectrums under two ways: driving cavity and driving atoms. We demonstrate that driving atoms can be considered as a method to obtain the position information of atoms. This research has very practical application values on obtaining the position information of atoms in a cavity.</jats:p>