类锂氯离子和钾离子软X射线激光光谱理论计算

本文采用Hartree-Fock自洽场方法,从理论上计算了类锂氯离子和类锂钾离子可能实现软X射线激光的有关能级能量及跃迁谱线性质:跃迁波长、跃迁几率和振子强度。计算结果表明,类锂钾离子的部分跃迁非常有可能实现软X射线激光,并且其中有三条谱线的波长已进入水窗。     

Investigations on novel XUV-laser schemes

Short pulse laser generated plasmas interacting with a pulsed gas jet are studied to aid the realization of novel XUV laser schemes based on recombination supported by charge exchange pumping. Interaction of C⁴⁺, O³⁺ and O⁴⁺ ions with hydrogen and nitrogen indicates strong charge exchange pumping of C³⁺(3p-2s, 3d-2p) lines at 31.2 and 38.4 nm, and O²⁺ (2p3s-2p²) and O³⁺ (2s3d-2s²2p) lines at 37.4 and 23.8 nm. PACS 52.50.Jm; 52.25.Nr     

共振光泵X射线激光的抽运谱线和吸收谱线波长匹配实验

用octadecyl hydrogen maleate(OHM)晶体谱仪进行了4.5nm附近如下三组共振光泵X射线激光的抽运谱线和吸收谱线对波长匹配实验研究:SiXⅡ3d—2p,4.4021nm,MgX2s—4p,4.4050nm;CuXIX4f—3d,4.7329nm,MgX2p—4d,4.7310nm;和AIXI3p—2s,4.8338nm,MgIX2s²—2s4p,4.8340nm.其中第二组线对据我们所知尚未见报道.比较并讨论了这三组线对的优缺点. 关键词：     

New study on the XeVIII spectrum

Capillary light sources were used to observe the spectrum of seven-times-ionized xenon, XeVIII, in the 300-6000 Å wavelength range. Twenty-eight energy levels belonging to the 5s-9s, 5d-9d, 5g-9g, 7i-10i, 9l, 5p-9p, 4f-9f, 6h-9h and 8k-10k configurations were adjusted and 38 new spectral lines were classified. The XeVIII ionization energy was determined with improved accuracy using the polarization model. The analysis was supported by Hartree-Fock calculations. The weighted oscillator strengths for all the observed spectral lines were also calculated considering the fitted values for the energy parameters.     

Study of the Stark effect in xenon

A gas-discharge source of light is proposed for investigation of the Stark effect by the method of canal rays in fields of up to 200 kV/cm intensity. Measurements of displacements of 12 spectral lines of xenon in the region of 4300–5000 Å (2p-1s and 3p-1s transitions) were conducted. For seven spectral lines the Stark shifts were measured for the first time. On the basis of the measured shifts the constants of the quadratic Stark effect were determined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 35–40, July, 1973.     

Linear Interaction (Transformation) of de Broglie Waves of the Γ- and X-Valleys and Intraband Optical Transitions in GaAs/AlAs Quantum-Well Heterostructures in a Lateral Electric Field

We discuss the linear interaction between the de Broglie waves of different electron valleys in heterostructures where a constant electric field is applied along the heterointerfaces (lateral field). The probabilities of phononless and dipole optical transitions of electrons between the - and X-subbands in GaAs/AlAs quantum-well heterosructures with a lateral electric field are calculated. It is shown that the electric field has a strong effect on the probabilities of phononless and direct optical dipole -X electron transitions. Moreover, a lateral electric field changes the spectrum of the intersubband -X light absorption, i.e., there is an intersubband analogue of the Franz-Keldysh effect. The considered linear interaction of de Broglie waves is compared with the well-known cases of linear wave interaction in a magnetized plasma, the Zener breakdown, and the Franz-Keldysh effect in solids.     

类锂硅离子能级结构及软X射线激光光谱理论计算

本文采用Hartree-Fock自洽场方法,从理论上计算出类锂硅离子1s~2nl(n=2～7,l=0～5)各能级能量,并给出在极紫外(波长小于400(?))范围内各跃迁谱线的光谱性质、波长、振子强度和跃迁几率.对实验中已实现软X射线激光的跃迁(5d-3p,5f-3d,6d-3p,6f-3d),计算所得的跃迁波长与实验值完全相符.与现有文献的波长比较,相对误差不超过1%.     

Theoretical study of the 5p56s – 5p6 spectra of neutral xenon

Recent high precision measurements on the lifetime of the metastable 6s[3/2]₂ state of atomic xenon display a difference with previous predictions by a factor of 2–3. In the present work, a systematic relaxation and correlation approach, which has been developed on the basis of a widely used multi-configuration Dirac-Fock method, is applied to study the electric dipole allowed E1 and forbidden M1, E2 and M2 transitions between the 5p⁵ 6s and 5p⁶ configurations. We systematically include the correlation effects which arise from all the single and double excitations from the occupied shells into the (n=6–10) active sets and the relaxation effects caused by change of the electron density between the radiative initial- and final-states. This study not only reduces greatly the existing discrepancy in the lifetime of the 6s[3/2]₂ state, but also presents rather consistent results for both the lifetime of the metastable 6s'[1/2]₀ state and the oscillator strength of the 5p⁵ 6s - 5p⁶ E1 resonant transitions.     

Stimulated multipole Raman scattering between opposite-parity states of atomic potassium

Stimulated multipole Raman scattering by free atoms has been observed for the first time. Tunable Stokes emissions close to the 3d-4p transitions in potassium vapour were readily detected when the incident laser frequency was tuned in the region of the 4s-3d electric quadrupole resonances.     

Ultra-sensitive in-beam \gamma -ray spectroscopy for nuclear astrophysics at LUNA

Ultra-sensitive in-beam -ray spectroscopy studies for nuclear astrophysics are performed at the LUNA (Laboratory for Underground Nuclear Astrophysics) 400 kV accelerator, deep underground in Italy’s Gran Sasso laboratory. By virtue of a specially constructed passive shield, the laboratory -ray background for < 3 MeV at LUNA has been reduced to levels comparable to those experienced in dedicated offline underground -counting setups. The -ray background induced by an incident -beam has been studied. The data are used to evaluate the feasibility of sensitive in-beam experiments at LUNA and, by extension, at similar proposed facilities.     

Structurally asymmetric d.c. SQUID’s in the presence of coupling energy inhomogeneity of the junctions studied by means of the reduced two-junction interferometer model

The effects of structural asymmetries and of inhomogeneities in the junction parameters on the electrodynamic response of conventional d.c. SQUIDs are studied both analytically and numerically. By a first-order perturbative expansion with respect to the parameter and to the deviation parameters describing structural asymmetry and inhomogeneity, we write the reduced dynamical equation for the average superconducting phase difference of a conventional d.c. SQUID. As in homogeneous and symmetric SQUIDs, the resulting dynamical equation is seen to be similar to that of a single junction with an unconventional current-phase relation characterized by a second harmonic contribution; in addition, a cosine term appears as a consequence of superconducting coupling inhomogeneity. By means of the reduced dynamical equation, the I-V characteristics in the presence of an external rf field and the critical current of the device are studied in the absence of noise.     

New cascade laser transitions in CH2F2 pumped with the 9R32 line of a cw CO2 laser

New cascade laser transitions of¹²CH₂F₂ at 172.50m, 208.83m, 220.44m, 223.99m and 250.61m are reported. A waveguide FIR laser was pumped with a quasi cw¹²C¹⁶O₂ laser operating on the 9R32 line. Together with the already known lines at 184.3m, 196.1m and 235.9m, the laser lines can be assigned to rotational transitions in the ₉ vibrational band of¹²CH₂F₂ and to refill transitions of the vibrational ground state ₀.     

Optogalvanic spectra of calcium in the 6090–6760 Å region

Optogalvanic spectra of some 30 transitions of calcium originating from the ground state as well as from several excited states (4s4p ^1,3P, 4s3d ^1,3D, 4s5p ³P, 3d4p ³D, ³F) have been investigated using laser-irradiation of a low-current glow discharge in a thermionic diode. The influence of various experimental parameters such as bias field, oven temperature and buffer gas pressure on the spectra are reported. Seven previously unreported transitions are recorded including four forbidden transitions which violate the J selection rules. An interesting anomaly observed in the non-statistical population of the 4s3d ³D_3,2,1 multiplet is discussed where the populations of ³D₃:³D₂:³D₁ are in the ratio of 94:5:1. A possible explanation is based on avoided crossing between potential energy curves of the Ca-Ar molecule.     

SU(5) symmetry of spdfg interacting boson model

The extended interacting boson model with s-, p-, d-, f- and g-bosons included (spdfg IBM)is investigated. The algebraic structure including the generators, the Casimir operators of the groups at the SU(5) dynamical symmetry and the branching rules of the irreducible representation reductions along the group chain are obtained. The typical energy spectrum of the symmetry is given.     

Excitation of magnesium ions in slow electron-ion collisions

The method of intersecting modulated beams was used to measure the absolute excitation functions of 3s-3p and 3p-4s transitions of MgII in collisions of electrons with magnesium ions at energies between the threshold of excitation and 100 eV.     

Active demultiplexing of single photons from a solid‐state source

A scheme for active temporal‐to‐spatial demultiplexing of single photons generated by a solid‐state source is introduced. The scheme scales quasi‐polynomially with photon number, providing a viable technological path for routing n photons in the one temporal stream from a single emitter to n different spatial modes. Active demultiplexing is demonstrated using a state‐of‐the‐art photon source—a quantum‐dot deterministically coupled to a micropillar cavity—and a custom‐built demultiplexer—a network of electro‐optically reconfigurable waveguides monolithically integrated in a lithium niobate chip. The measured demultiplexer performance can enable a six‐photon rate three orders of magnitude higher than the equivalent heralded SPDC source, providing a platform for intermediate quantum computation protocols.

     

Multi‐peak and chromaticity‐stable top‐emitting white organic light‐emitting diodes using single blue emitter

We have fabricated multi‐peak and chromaticity‐stable top‐emitting white organic light‐emitting diodes (TEWOLEDs) using single blue emitter. Besides the intrinsic emission of blue emitter, the additional emission can be well realized by simply adjusting the thickness of hole transporting layer (HTL), thus modifying the optical cavity length to obtain different resonant wavelengths. The detailed variation process for multi‐peak spectra with the increase of HTL thickness is studied, which provides a guidance for the design of microcavity TEWOLEDs.

     

Calculation of linear and nonlinear optical absorption coefficients of a spherical quantum dot with parabolic potential

In the effective mass approximation, we calculated the binding energy and wave function for the 1s-, 1p-, 1d- and 1f-states of a spherical quantum dot (QD) with parabolic potential by using a combination of quantum genetic algorithm (QGA) and Hartree-Fock-Roothaan (HFR) method. In addition, we also investigated the linear and the third-order nonlinear optical absorption coefficients as a function of the incident photon energy for the 1s-1p, 1p-1d and 1d-1f transitions. Our results are shown that the existence of impurity has great influence on optical absorption coefficients. Moreover, the optical absorption coefficients are strongly affected by the incident optical intensity, relaxation time, parabolic potential and dot radius.     

Dielectric and charge transport properties of the spin crossover complex [Fe(Htrz)2(trz)](BF4)

Spin crossover compounds are considered to be a viable alternative for creating display, memory and switching devices due to the bistability of their magnetic, optical, mechanical and electrical properties. This Letter presents the study of the dielectric and transport properties of the [Fe(Htrz)₂(trz)](BF₄) (Htrz = 1H‐1,2,4‐triazole) complex in a wide temperature and frequency range. Our results reveal a singular behavior of the dielectric modulus upon the spin transition in conjunction with the switching of the conductivity between the high spin and low spin states.

     

PT symmetry in a fractional Schrödinger equation

We investigate the fractional Schrödinger equation with a periodic ‐symmetric potential. In the inverse space, the problem transfers into a first‐order nonlocal frequency‐delay partial differential equation. We show that at a critical point, the band structure becomes linear and symmetric in the one‐dimensional case, which results in a nondiffracting propagation and conical diffraction of input beams. If only one channel in the periodic potential is excited, adjacent channels become uniformly excited along the propagation direction, which can be used to generate laser beams of high power and narrow width. In the two‐dimensional case, there appears conical diffraction that depends on the competition between the fractional Laplacian operator and the ‐symmetric potential. This investigation may find applications in novel on‐chip optical devices.