One-electron spectrum of Yb+: Relativistic energies,transition probabilities and dipole polarizability

Calculations are reported of relativistic ionization energies and transition probabilities in the one-electron spectrum of singly-ionized ytterbium. The relativistic model potential approach used takes into account both valence-core electron exchange and correlation. The influence of polarization of the core by valence electrons on ionization energies and transition probabilities has been studied. Strong cancellation effects have been found for higher transitions of the principal series; these affect both transition probabilities and relative line strengths. The energies are predicted for some states which have not yet been experimentally localized. The static dipole polarizability for Yb⁺ is estimated to be 48.18 g₀³ from computed oscillator strengths; this estimate is compared with lower bounds determined from experimental data.     

An application of a new harmonic-oscillator basis to the calculation of trinucleon ground-state observables

A new harmonic-oscillator basis for trinucleon ground-state calculations is introduced, featuring different oscillator radii for the two intrinsic variables. This basis allows charge-dependent interactions to be handled and seems to yield a better convergence with respect to the previously used oscillator bases. A test calculation with the Reid soft-core interaction is presented. The resulting (extrapolated) triton binding energy is 7.3 ± 0.2 MeV, and the first minimum in the ³He charge form factor occurs at q² = 13.1 fm^?2.     

Synthesis of CdZnO thin film as a potential candidate for optical switches

Cadmium doped zinc oxide thin films have been prepared using a thermal decomposition technique. The influence of Cd as a doping agent on the structure, optical and nonlinear optical properties was carefully investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and a UV-vis spectrophotometer. A deep correlation has been found between the surface roughness and the optical properties. The roughness is found to deteriorate the nonlinear response, such that the highest nonlinear susceptibility χ⁽³⁾ is obtained for the smoothest layer. The third-order nonlinear susceptibility χ⁽³⁾ has been calculated using the Frumer model, and is estimated to be 3.37×10⁻¹⁰ esu. The dispersion of the refractive index of the prepared thin film is shown to follow the single electronic oscillator model. From the model, the values of oscillator strength (E_d), oscillator energy (E_o) and dielectric constant (ε_∞) have been determined. The conductivity has been measured as a function of the energy of the photons, revealing marginal change at energies below 3.15 eV, while above this value there is a large increase in the conductivity. This suggests that CdZnO is a potential candidate for applications in optical devices such as optical limiter and optical switching.     

A new emission band spectrum of sulphur

A new emission band system of S₂ has been obtained in the region λ 3050–λ 2670 when sulphur is excited in a 30 mc/S. high frequency discharge from a 1/2 kW oscillator. The bands appear single sharp headed and are degraded towards red. Analysis of these new bands as belonging to a single system has led to the following vibrational formula.ν=36624·7+428·5(v′+1/2)?3·45(v′+1/2)² ?699·2(v″+1/2)+3·2(v″+1/2)². This system disignated as (b?x) is tentatively assigned to the electronic transition¹∑ _u ⁺ ?¹∑ _g ⁺ . The¹∑ _g ⁺ (x) state is found as the common lower state of three of the far ultraviolet systems of S₂ recently reported byTanaka andOgawa.     

Quartic oscillator potential in the γ-rigid regime of the collective geometrical model

A prolate γ-rigid version of the Bohr-Mottelson Hamiltonian with a quartic anharmonic oscillator potential in β collective shape variable is used to describe the spectra for a variety of vibrational-like nuclei. Speculating the exact separation between the two Euler angles and the β variable, one arrives at a differential Schrödinger equation with a quartic anharmonic oscillator potential and a centrifugal-like barrier. The corresponding eigenvalue is approximated by an analytical formula depending only on a single parameter up to an overall scaling factor. The applicability of the model is discussed in connection to the existence interval of the free parameter, which is limited by the accuracy of the approximation, and by comparison with the predictions of the related X(3) and X(3)-β ² models. The model is applied to qualitatively describe the spectra for nine nuclei which exhibit near-vibrational features.     

Oscillator parameters of transverse phonons in <Emphasis Type="Italic">a</Emphasis>-domain lead titanate

The temperature behavior of polarized Raman spectra of a-domain PbTiO₃ single crystals has been investigated. The spectra obtained are fit by a damping harmonic oscillator model with allowance for a complex background structure. A full set of oscillator parameters of all phonon modes in the frequency range 12 < ν < 1200 cm^?1 is obtained and their temperature dependences in the range from 300 to 800 K are presented.     

Oscillator strengths and polarizabilities of the hot-dense plasma-embedded helium atom

The effect of weakly coupled hot plasma environment on the oscillator strengths of the ultraviolet and visible series and the polarizabilities of helium has been investigated using variational highly correlated wave functions within the non-relativistic framework. The Debye shielding approach that admits a variety of plasma conditions is used to simulate the plasma effects. For each shielding parameter, dipole oscillator strengths are calculated for the 1 ¹S-n¹P (n=2, 3), 2 ¹S-2 ¹P, 2 ³S-n³P (n=2, 3) and 2 ^1,3P-n^1,3D (n=3, 4) transitions. The dipole and quadrupole polarizabilities for the ground He (1s²¹S) state are also reported for each screening parameter. Results obtained are useful in plasma diagnostic purposes besides several other applications.     

The microwave spectrum of methyl isothiocyanate

New measurements of microwave transitions of CH₃NCS in the region 14–40 GHz are reported. Assignments of several sets of lines in terms of the transitions expected for a pseudosymmetric-top molecule are suggested and a tentative extension of the analysis to cover all the k = 0 lines in our spectra and in the region 5–11 GHz is proposed. Preliminary calculations using a two-dimensional anharmonic oscillator model lead to a bending potential with a central hump of some 160 cm^?1, and a minimum-energy configuration at a CNC bond angle of about 147°. A correlation between rovibrational energy levels of a two-dimensional anharmonic oscillator and those of an asymmetric-top molecule with a bent skeleton and freely rotating methyl group is proposed.     

On the path integral for the potential V = ar−2 + br2

A simple, alternative path integral formulation for the potential V = ar^?2 + br², r ? 0, is presented. This is achieved by mapping the problem to a two-dimensional oscillator and using the method of image paths.     

Determination of oscillator strengths from the self-absorption of resonance radiation in rare gases

A method is presented which determines directly oscillator strengths for rare gas atoms from the selfabsorption of resonance radiation. It is shown that under suitable experimental conditions the oscillator strength can be derived from the selfabsorption by a simple formalism. Some problems concerning this method are treated in detail, such as reemission of absorbed radiation and the presence of more than one isotope. A value of 0.262±0.018 was obtained for the oscillator strength of the He(1¹S→2¹P) resonance transition. Preliminary data were also obtained for some resonance transitions in neon, using neon gas with a natural abundance of the isotopes.     

Properties of single picosecond pulses from neodymium:Phosphate glass

Streak camera detection has been used to determine the temporal characteristics of pulses from Nd:phosphate glass used as a mode-locked laser oscillator and as an amplifier. The frequency doubled pulses are not transform limited (Δν = 46 cm^-1, Δt = 6 ps). The fourth harmonic has a spectral bandwidth of 11 cm^-1 and is tunable across the full bandwidth of the second harmonic. Temperature tuning characteristics and efficiencies for harmonic generation are described. A comparison is made with the properties of Nd:silicate glass.     

An investigation of the scaled modified oscillator potential

In the second volume of their book Nuclear structure, Bohr and Mottelson propose that in the modified oscillator potential the spin-orbit term and the l² term should be scaled according to the deformation of the potential. This scaling has been studied in detail, and some of its more general consequences are discussed. The single-particle parameters κ and μ have been fitted for nuclei in the rare earth region, for lead and for actinides. The scaled potential has been used for a detailed investigation of the nuclei in the actinide region, including calculations of potential energy surfaces, fission barriers and ground-state masses. Both symmetric and reflection asymmetric deformations have been considered and the results thus obtained with the scaled potential have been compared to those obtained with the modified oscillator potential and the folded-Yukawa potential.     

A new method for the production of atomic beams of highly refractory elements and first atomic beam magnetic resonances in Ta181

A new universal method for the production of atomic beams of highly refractory elements has been developed. The beams of free atoms are produced by locally heating a small area on a target consisting of the material to be evaporated. The local heating is achieved via the focussed electron beam of a commercial electron gun. The atomic beams so obtained are suitable for studying hyperfine structures by the atomic beam magnetic resonance method. The first observedrf resonances in the ground state⁴ F _3/2 and the first excited state⁴ F _5/2 of Ta¹⁸¹ are reported.     

全固化自锁模飞秒Ti:S激光器实验研究

首次在国内系统报道了以腔内LBO倍频Nd:YVO₄激光器为泵浦源的全固化自锁模飞秒钛宝石激光器的实验结果.设计了一种热不敏腔内LBO倍频线性折叠腔结构,获得到了25.5%的光转换效率,泵浦功率为22W时得到了5.6W的基模绿光输出功率;以该激光器为泵浦源,在线性Z型腔的基础上,使用了一种能够通过改变腔内凹面聚焦镜折叠角消除象散的方法,直接由钛宝石激光器得到了脉冲宽度为22fs、功率为300mW的光脉冲.整个激光系统稳定性好,噪音明显低于Ar³⁺激光器的泵浦情况.     

Radiative lifetimes and absolute oscillator strengths for the SiOAΠ-XΣ transition

Measurement of a radiative lifetime of 9.6 ± 1.0 nsec for the SiOA¹Π-state is reported. RKR Franck-Condon factors have been computed and, with these, absolute oscillator strengths are calculated. A band system at ∼ 3022Å has been found that may be due to SiO⁺, but the band is not resolved at our experimental resolution, and identification remains uncertain. The upper state of the carrier of this spectrum has a radiative lifetime of 8.3 ± 0.8 nsec.     

Optical oscillator strengths for Be II and B III

A simple two-parameter analytic potential adjusted so as to produce the experimental energy levels is used to generate wave functions for the ground and excited states of the ions Be II and B III. Using these wave functions we calculate optical oscillator strengths for various excitations from the 1s ²2s(² S) ground state. The results are compared to experiment and other calculations.     

Time-resolved Fourier transform infrared spectroscopy: Application to pulsed discharges

Time-resolved Fourier transform spectroscopy (TR-FTS) is reviewed, with emphasis on synchronous FTS using continuously scanning interferometers. By using a high-resolution Bruker IFS 120 HR, a TR-FTS method has been developed with the help of a microcontroller SX, where a maximum of 64 time-resolved data are recorded with a preset time interval in a single scan of the interferometer. The time resolution is 1 μs, limited by the response time of the detector system used. This method has been applied to a pulsed discharge in an Ar and H₂ mixture to observe time profiles of ArH⁺ and ArH emission spectra. Electronic transitions of He₂ have been observed in the infrared region with this method, and from the time profiles, He₂ in Rydberg states with higher energy than the b³Π state is found to be produced efficiently in afterglow plasma. Fifteen bands in the 2300-8000 cm⁻¹ region have been assigned by using previously reported data from the optical region. A new band from the 5f state has been assigned for the first time through the 5f-4d band in the 2600 cm⁻¹ region.     

Photoionization cross sections and oscillator strengths of neutral cesium

The absolute photoionization cross sections from the 6p ²P_1/2 excited state of cesium at threshold and above the threshold region have been measured using the saturation absorption technique. The photoionization cross section at the ionization threshold is determined as 22.6±3.6 Mb, whereas in the region above threshold its value ranges from 22 to 20 Mb for photoelectron energies up to 0.1 eV. A comparison of the photoionization cross sections with earlier reported theoretical and experimental data have been presented and are in good agreement within the uncertainty. In addition, the oscillator strengths of the 6p ²P_1/2→n d ²D_3/2 (21≤n≤60) Rydberg transitions of cesium have been calibrated using the threshold value of the photoionization cross section. A complete picture of the oscillator strengths from the present work and previously reported data from n=5–60 is presented.     

The effect of an external electric field on the optical properties of a quantum-dot molecule with a resonant state of the D 2 − center

The effect of an external electric field on the probability of the electron radiative transition from a resonant u-state to the localized g-state of the D ₂ ^? center in the presence of dissipative tunneling has been investigated in the model of zero-radius potential. It is shown that the probability of radiative transition increases by about two orders of magnitude in the case of the external electric field intensity for which the initially asymmetric double-well oscillator potential simulating a quantum-dot molecule becomes symmetrical.     

A new Morse-oscillator based Hamiltonian for H3+: Calculation of line strengths

In two recent publications [V. Špirko, P. Jensen, P. R. Bunker, and A. Čejchan, J. Mol. Spectrosc. 112, 183–202 (1985); P. Jensen, V. Špirko, and P. R. Bunker, J. Mol. Spectrosc. 115, 269–293 (1986)], we have described the development of Morse oscillator adapted rotation-vibration Hamiltonians for equilateral triangular X₃ and Y₂X molecules, and we have used these Hamiltonians to calculate the rotation-vibration energies for H₃⁺ and its X₃⁺ and Y₂X⁺ isotopes from ab initio potential energy functions. The present paper presents a method for calculating rotation-vibration line strengths of H₃⁺ and its isotopes using an ab initio dipole moment function [G. D. Carney and R. N. Porter, J. Chem. Phys. 60, 4251–4264 (1974)] together with the energies and wave-functions obtained by diagonalization of the Morse oscillator adapted Hamiltonians. We use this method for calculating the vibrational transition moments involving the lowest vibrational states of H₃⁺, D₃⁺, H₂D⁺, and D₂H⁺. Further, we calculate the line strengths of the low-J transitions in the rotational spectra of H₃⁺ in the vibrational ground state and in the ν₁ and ν₂ states. We hope that the calculations presented will facilitate the search for further rotation-vibration transitions of H₃⁺ and its isotopes.