Trend of shape resonance-induced features in the angular distribution parameter as a function of photon energy for carbon,silicon and germanium tetrac

The angular distribution parameter as a function of photon energy, β(hν), has been measured in the 13–27 e V range using synchrotron radiation for the five valence orbitais in silicon and germanium tetrachlorides. The results have been compared with those previously reported for carbon tetrachloride. In particular, the trend of shape resonanceinduced features has been followed along the valence isoelectronic series CCl₄-SiCl₄-GeCl₄ for the 1e and 2t₂ orbitals. As the atomic number of the central atom increases, the shape resonances move toward the threshold ionization energy for a particular molecular orbital.     

Delayed onset of 4d photoemission relative to the giant 4d photoabsorption of La

For the giant 4d photoabsorption of La, both the total photoabsorption spectrum and the N_4.5-derived Auger emission intensity spectrum increase significantly above hν ? 112 eV, with spectral peaks at hν = 118 and 119 eV, respectively. However, the predominant 4d photoemission partial cross section shows a delayed onset of ～ 4 eV, with a peak at hν = 121 eV, while the 5s, 5p, and 5d partial cross sections all show a strong resonant enhancement at lower energies, with spectral peaks at hν = 116.6 eV. These results are compared with a recent many-body calculation for Ce. The photon energy dependence of the La 4d_{$\text{5}\text{2}$}/4d_{$\text{3}\text{2}$} photo-emission branching ratio is consistent with a “final-state model.”     

Photoemission from laser excited semiconductors: Dynamic response of the electronic structure in Si

Using angle-resolved photoemission in coincidence with a pulsed Nd:Yag laser beam (hν_L = 2.33 eV), we have studied the dynamic rearrangement of the electronic states in Si in the presence of a large number of electron hole pairs created by laser photon excitation. We observed considerable changes in the valence band structure, a renormalization of the bandgap, and a satellite peak in the 2p core level emission due to more effective core hole screening.     

Optical and magneto-optical spectroscopy of thin ferromagnetic InMnAs layers

Spectral dependences of the refractive n(hν) and absorption k(hν) indices (hν= 1.2–4.4 eV) and the magneto-optical constant δ(hν) (hν = 0.5–4.4 eV) of the transverse Kerr effect of the InMnAs layers produced by laser deposition have been studied. The spectra of the diagonal ?(hν) and off-diagonal ?′hν) components of the permittivity tensor of the layers have been found. A comparison of the spectral dependences δ(hν), ?′(hν) and ?′₂ × (hν)² of the InMnAs and MnAs layers have been performed. Features in the spectra of the InMnAs layers have been attributed to a competition between the contributions of the In_{1 ? x} Mn _x As matrix and MnAs inclusions.     

PbB_4O_7晶体的太赫兹光谱和软光学声子

对实验测量的PbB4O7晶体样品的太赫兹(1012Hz)光谱、拉曼光谱以及红外—可见—紫外光谱进行了分析.在0.25—2.5THz波段介电函数随频率变化曲线ε(ν)出现共振型尖峰.四方面的分析表明PbB4O7晶体中存在软光学声子:1)介电函数随频率的变化曲线ε(ν)满足LST(Lyddane-Sachs-Teller)关系;2)在共振峰的频率附近(3.10THz)有很强的拉曼散射峰;3)吸收系数随频率的变化曲线α(ν)满足极化激元的特征;4)透过晶体的光子的色散关系ν(k)发生断开的畸变.PbB4O7晶体中存在软光学声子的意义在于,在满足产生极化激元的条件下,透过晶体的光子的频率会发生劈裂,分为升高和降低的两支,有可能利用这种原理来改变光子的频率.     

Probability distribution functions for a single-particle vibrating in one dimension: experimental study and theoretical analysis

We consider the form of the rebound velocity, ν₀, particle velocity, ν, and height, h, probability density functions (PDFs) for the one-dimensional motion of a single particle on a sinusoidally oscillating base. The motion is considered in the limit of high excitation (vibration frequency ⪢ collision rate). Experimentally, we find that these PDFs are well-approximated by P_ν0(ν₀) ∞ ν₀ exp(− αν₀²), a Gaussian P_ν(ν) ∞ exp(− αν²) and a Boltzmann-type function P_h(h) ∞ exp(− 2αgh), where α is a constant and g is the acceleration due to gravity. We develop an analytical model which accurately predicts the general form for the rebound velocity PDF; the other two PDFs are then analytically shown to follow as a consequence. Scaling laws for the particle granular temperature with peak base velocity and particle-base restitution coefficient, determined from previous work, can also be predicted from the PDF. A fine scale “spiky” structure in the rebound velocity PDF is found, using numerical simulations, to be a consequence of resonance phenomena between the particle and vibrating base. Good agreement between scaling laws from the theory and simulation is found but insufficient data is obtainable to derive accuracy exponents experimentally.     

A study of core and valence levels in β-PbO2 by hard X-ray photoemission

The core and valence levels of β-PbO₂ have been studied using hard X-ray photoemission spectroscopy (hν = 6000 eV and 7700 eV). The Pb 4f core levels display an asymmetric lineshape which may be fitted with components associated with screened and unscreened final states. It is found that intrinsic final state screening is suppressed in the near-surface region. A shift in the O 1s binding energy due to recoil effects is observed under excitation at 7700 eV. It is shown that conduction band states have substantial 6s character and are selectively enhanced in hard X-ray photoemission spectra. However, the maximum amplitude in the Pb 6s partial density of states is found at the bottom of the valence band and the associated photoemission peak shows the most pronounced enhancement in intensity at high photon energy.     

Merging of X-Ray photons in the field of a light atomic ion

The process of merging of three X-ray photons into one photon in the field of a light atomic ion is theoretically studied. A pronounced resonance structure and a strong angular anisotropy of the differential cross section for merging are predicted in the region of the incident photon energy ?ω ? I _1s /2 (I _1s is the threshold energy of ionization of the -shell of the ion). The magnitude of the observed merging cross section is estimated.     

Simultaneous solution of Kompaneets equation and radiative transfer equation in the photon energy range 1-125 keV

Radiative transfer equation in plane parallel geometry and Kompaneets equation is solved simultaneously to obtain theoretical spectrum of 1-125 keV photon energy range. Diffuse radiation field are calculated using time-independent radiative transfer equation in plane parallel geometry, which is developed using discrete space theory (DST) of radiative transfer in a homogeneous medium for different optical depths. We assumed free-free emission and absorption and emission due to electron gas to be operating in the medium. The three terms n, n² and (∂n/∂x_k) where n is photon phase density and x_k=(hν/kT_e), in Kompaneets equation and those due to free-free emission are utilized to calculate the change in the photon phase density in a hot electron gas. Two types of incident radiation are considered: (1) isotropic radiation with the modified black body radiation I^MB[1] and (2) anisotropic radiation which is angle dependent. The emergent radiation at τ=0 and reflected radiation τ=τ_max are calculated by using the diffuse radiation from the medium. The emergent and reflected radiation contain the free-free emission and emission from the hot electron gas. Kompaneets equation gives the changes in photon phase densities in different types of media. Although the initial spectrum is angle dependent, the Kompaneets equation gives a spectrum which is angle independent after several Compton scattering times.     

On the vibrational state dependence of the asymmetry parameter of angular distribution in the photoelectron spectra

A discussion is given on the changes obtainable in the asymmetry parameter β with vibrational state of the ion in the approximation involving fixed direction of body-frame orientation during the electron ejection. The R dependence of the electronic matrix elements is taken into account by calculation of appropriate displaced oscillator integrals. Inclusion of a nuclear matrix element gives in most cases negligible effect for the direct ionization. β_ν′ are calculated for H₂ and N₂. Expected variations in β_ν′ are compared with recent experimental data on N₂ and CO. Higher partial waves and their effect on β_ν′ are discussed.     

Laser-radiofrequency double-resonance spectroscopy of formic acid: Assignment and analysis of the ν6 and ν8 bands

The highly sensitive method of infrered-radiofrequency double resonance inside a carbon dioxide laser cavity has been used to observe direct K-type doubling transitions in formic acid. Radiofrequency transitions corresponding to both ν₆ and ν₈ bands were observed. In the light of these new data some earlier infrared laser measurements are now assigned unambiguously. This results in greatly improved band parameters and a $\text{ν}{}_6\text{ν}{}_8$a-type Coriolis coupling constant that is 10 times better defined.     

2D-to-3D percolation crossover of metal-insulator composites

Percolation properties and d.c. conductivity were determined for an L²×h-random resistor network model of metal-insulator composite films. The effects of the thickness h on the percolation threshold and conductivity were studied numerically in the limit of an infinite size of the L²-plane parallel to the film. For thicknesses ranging from h/L=0.01 to h/L=0.24, a crossover between a finite-size regime and a saturation regime was observed at h/L≈0.1. In the finite-size regime (h/L?0.01), the percolation threshold scales as pc(h)−pc3∝h−1/x, the exponent x being compatible with that of the critical exponent of the 3D correlation length, ν₃. The conductivity exponent t appeared to depend linearly on the ratio h/L with a slope νD compatible with 2+ν₂, where ν₂ is the 2D correlation length exponent. In the saturation regime, a scaling correction for the percolation threshold was found with an exponent 1+1/ν₃. In this regime we also observed a logarithmic dependence of the conductivity exponent on h/L.     

A Structural and Ellipsometric Investigation of Thin Gallium Oxide Layers Deposited on Si by Means of Laser Deposition

The morphology of Ga₂O₃ layers deposited on a silicon substrate by pulse laser deposition is studied using scanning electron microscopy in the thickness range of 30–200 nm. Using spectroscopic ellipsometry in the wavelength range from 250 to 900 nm, the thickness of layers and dispersion of their optical parameters (complex pseudodielectric function ε, refractive and absorptive indices) have been determined and the fraction of voids has been estimated in the scope of the Bruggeman effective medium approximation. In the spectrum of the imaginary part ε₂, there is observed an increase in values in the region of energy E = 4.8 eV corresponding to the direct interband transition in the Ga₂O₃ structure. X-ray structure analysis showed the presence of peaks typical for the β-Ga₂O₃ structure. The results of the investigations can be used for the formation of wide-bandgap gallium oxide layers in developing devices of power electronics and in creating optoelectronic devices for the UV range.     

Polar phonons and specific features of the ferroelectric states in cadmium titanate

Polarized spectra of reflectance R(ν) and transmittance Tr(ν) of single-crystal CdTiO₃ samples have been obtained in the frequency range 7 < ν < 1000 cm^?1 and for temperatures from 5 to 300 K using IR Fourier spectroscopy and submillimeter-range techniques. Dispersion analysis was carried out in terms of the additive-oscillator model, and dielectric responses ε(ν) and ε″(ν) were calculated. The polar modes were assigned to particular symmetry types, and their oscillator parameters (dielectric contributions, normal frequencies, damping constants) were determined. The numerical values of the components of the static permittivity tensor, ε₁₁ and ε₃₃, are shown to be almost fully determined by the total dielectric contributions due to the B_3u and B_1u phonons, respectively. In the low-frequency domain, lines showing anomalous behavior of the oscillator parameters, which is characteristic of soft ferroelectric modes, were observed. It is shown that, in CdTiO₃ at cryogenic temperatures, there exist several different polar states with switching in the direction of the spontaneous polarization vector.     

On the Deser,Gilbert, Sudarshan representation for functions Wi(ν, q2)(i = 1, 2) describing the electroproduction process

The Deser, Gilbert, Sudarshan representation (D.G.S.R.) for the functions W_i(ν, q²) (i = 1,2) is considered as equations determining spectral functions h_i(a, α) via the values W_i(ν, q²) in the physical region of the electroproduction channel. It is shown that if W_i(ν, q²) obey the microcausality and spectrality conditions, then the equations for h_i(a, α) have solutions in the class of Schwartz temperated distributions and thereby the D.G.S.R. is proved. Formulae are obtained expressing spectral functions in the D.G.S.R. through the values of functions W_i(ν, q²) in the physical region of the electroproduction channel.     

The effect of plasmon mass on spin light of neutrino in dense matter

We develop the theory of spin light of neutrino in matter (SLν) and include the effect of plasma influence on the emitted photon. We use the special technique based on exact solutions of particles wave equations in matter to perform all the relevant calculations, and track how the plasmon mass enters the process characteristics including the neutrino energy spectrum, SLν rate and power. The new feature it induces is the existence of the process threshold for which we have found the exact expression and the dependence of the rate and power on this threshold condition. The SLν   spatial distribution accounting for the above effects has been also obtained. These results might be of interest in connection with the recently reported hints of ultra-high energy neutrinos E=1÷10 PeV$E=1÷10\text{PeV}$ observed by IceCube.     

Gamow-teller transitions in β-decay of 66 146 Dy80

The β-decay of¹⁴⁶Dy₈₀ was studied by γ-ray and conversion electron spectroscopy following on-line mass separation. 58 % of the β-decay proceeding to a group of levels close to 2 MeV excitation is attributed to GT-decay of (πh ₁₁ ^2/2 )₀₊ pairs populating (πh_11/2νh_9/2νj ₀ ^?2 )1⁺ states in¹⁴⁶Tb₈₁. The total decay strength is significantly higher than found in¹⁴⁸Dy₈₂ decay, which arises from GT-transitions involving the ν-holes.     

Valence and C 1s core level photoelectron spectra of camphor

The valence photoelectron spectrum of camphor has been recorded with 95 eV synchrotron radiation, with better definition than previous He I spectra. The spectrum is interpreted by comparison with these He I results and with the aid of an outer-valence Green’s Function calculation of the orbital ionization energies. These calculations closely reproduce the observed vertical ionization energies in the outer valence region. A core level spectrum of the C 1s region (hν=357.9 eV) is also presented and reveals a marked shift of the carbonyl carbon relative to all others in the molecule.     

Frequency splitting phenomenon of dual transverse modes in a Nd:YAG laser

We observed frequency splitting phenomenon of dual transverse modes (TEM_00q and TEM_01q) in a Nd:YAG microchip standing wave laser utilizing intracavity stress birefringence effects. Four resonance frequencies (ν_00qe, ν_00qo, ν_01qe, and ν_01qo, respectively) were produced and tuned by changing the diametral compression force applied on the laser crystal. The transverse mode frequency spacing for the same longitudinal mode number (Δν_trans) was 1.16 GHz, and the magnitude of frequency splitting (Δν) ranged from 0 MHz to 1.16 GHz. Based on this phenomenon, a four-mode differential standing wave laser, whose signal characteristics were a little like those of a four-mode differential travelling wave laser gyro however with a much larger frequency splitting range, was produced. The theoretical analysis is in good agreement with the experimental results. This phenomenon not only can be used to make lasers with two or more frequency differences, but also can be used to make high-resolution self-sensing laser sensors (e.g. laser force sensors and laser accelerometers).     

Offset-locked CO2 waveguide laser study of formic acid: Reassessment of far-infrared laser assignments

A number of infrared transitions of formic acid were measured to a precision of better than 100 kHz. In the light of these new data, far-infrared laser measurements were reassessed. Available microwave data were also incorporated in deriving new parameters for the ν₆ and ν₈ states, including the $\text{ν}{}_6\text{ν}{}_8$a-type Coriolis interaction.