氢分子分立区和连续区(11.0—19.0 eV)的光学振子强度研究

利用通道规律,并考虑了转动分布对跃迁峰型的影响,对测量得到的绝对氢分子光吸收谱进行了分析．文中逐个确定了11.0—15.0 eV各振动态的振子强度,并得到了B′¹Σ⁺_u的解离强度．同时,利用多重散射Xα自洽场方法计算了氢分子分立区和连续区（11.0—19.0 eV）的光吸收谱．通过计算值和实验绝对测量值的比较可以说明,在自洽层次,文中理论计算值已能较好地说明本实验. 关键词：     

Structure of odd Ge isotopes with 40 < N < 50

We have interpreted recentlymeasured experimental data of ⁷⁷Ge, and also for ^73,75,79,81Ge isotopes in terms of state-of-the-art shell-model calculations. Excitation energies, B(2) values, quadrupole moments and magnetic moments are compared with experimental data when available. The calculations have been performed with the recently derived interactions, namely with JUN45 and jj44b for f _5/2pg9/2 space. We have also performed calculation for fpg _9/2 valence space using an fpg effective interaction with ⁴⁸Ca core and imposing a truncation to study the importance of the proton excitations across the Z = 28 shell in this region. The predicted results of jj44b interaction are in good agreement with experimental data.     

Simulation of structured 4T1→6A1 emission bands of Mn2+ impurity in Zn2SiO4: A first-principle methodology

A sequential, fully first-principle theoretical study of the Mn²⁺ green emission bands in the Zn₂SiO₄:Mn²⁺ phosphor is presented for the first time. A combined approach is developed based on the modern periodic density-functional theory and cluster ab initio wave-function-based electronic structure methods, the linear response theory for lattice phonons, and generating function formalism of vibronic spectra within the displaced multi-mode harmonic oscillator model. We obtain fairly good agreement between the calculated low- and high-temperature emission band positions, widths, zero-phonon lines and phonon wings and the available experimental emission studies, with special emphasis on Mn²⁺ distribution over two non-equivalent Zn²⁺ sites in the Zn₂SiO₄ material. An interpretation for vibronic structure observed in the low-temperature emission spectrum of this phosphor is suggested based on the present first-principle study.     

Two-photon absorption of tetraphenylporphin free base

We study two-photon absorption (TPA) spectra for toluene solution of 5,10,15,20-tetraphenyl-21H,23H-porphin (H₂TPP) in B and Q bands regions and find the maximum TPA cross-section values of 25 and 1-6 GM in laser wavelength ranges, 730-790 and 1100-1400 nm, correspondingly. In the 730-790 nm range the spectrum is attributed to parity allowed two-photon transition into g parity state, positioned nearby B state. Much lower TPA cross-section of ∼1 GM is measured for the transition into pure electronic Q state and it is due to the contribution of only those low-symmetry H₂TPP confomers, where mutual orientation of the porphyrin plane and the four phenyl rings lifts the center of inversion. The intermediate values of TPA cross-section of ∼6 GM are observed for the transition into vibronic Q states and are explained by TPA-allowed transition into vibronic states, which can occur even for totally centrosymmetrical molecules. Measurement of two-photon polarization ratio, Ω=σ_circ/σ_lin, shows that for parity allowed g→g transition Ω =1.05±0.05 and for transitions into electronic and vibronic Q-states, Ω=0.62±0.06 and 0.79±0.1 (depending on wavelength), respectively. Quantum-chemical calculations of both u and g parity excited energy levels of H₂TPP molecule are performed by CNDO/S method and the results are in good agreement with the experimental data.     

Stretch-Bender Calculations of the Rovibronic Energies in the Excited, ÃA1, Electronic State of NH2 and of the Near-Resonant High-Lying Levels of the X?B1 State

The extended stretch-bender Hamiltonian, incorporating spin-orbit coupling and overall rotation, has been used to calculate the spin-vibronic structure of the rovibronic energies in the region where the vibronic states of the excited òA₁ electronic state of NH₂ interact with near-resonant high-lying levels of the X?²B₁ state of NH₂. A detailed comparison has been made with the experimental measurements which were made of these rovibronic states, the majority of which are due to Ramsay, Vervloet, and their collaborators. We have shown that, as in our study of the vibronic levels of the X?²B₁ state below the barrier to linearity, in order to fit the variation of the effective vibronic spin-orbit coupling constant over the whole of this energy regime, the effective linear molecule spin-orbit coupling constant, A_SO must be increased from the earlier value of 50 cm⁻¹ of Ch. Jungen, K.-E. J. Hallin, and A. Merer (Mol. Phys.40, 65-94 (1980)) to 61.6 cm⁻¹. The impact of Fermi resonance, in both the òA₁ and X?²B₁ states, on the observed rovibronic structure has been assessed. The pattern of calculated spin-rovibronic levels, including the effects of spin uncoupling, is in good agreement with that measured experimentally.     

First-principles calculations of the structural, electronic and optical properties of cubic BxGa1−xAs alloys

Density functional calculations are performed to study the structural, electronic and optical properties of technologically important B_xGa_1−xAs ternary alloys. The calculations are based on the total-energy calculations within the full-potential augmented plane-wave (FP-LAPW) method. For exchange-correlation potential, local density approximation (LDA) and the generalized gradient approximation (GGA) have been used. The structural properties, including lattice constants, bulk modulus and their pressure derivatives, are in very good agreement with the available experimental and theoretical data. The electronic band structure, density of states for the binary compounds and their ternary alloys are given. The dielectric function and the refractive index are also calculated using different models. The obtained results compare very well with previous calculations and experimental measurements.     

Structure in the beta strength function of very neutron-rich Rb-isotopes

The beta strength functionS _β is calculated in a schematical Brown-Bolsterli model for the Gamow-Tellerβ ^? decay of^89–99Rb. The position of the peaks inS _β resulting from the back spin flip transitions and the calculated life-times are in good agreement with recent experimental results. A simple regularity is found to govern the energy position of the lowest-lying structures inS _β. By calculations of the type given here thus it should be possible to produce much more reliable input data concerningS _β forr-orn-process calculations than have been used up to now in astrophysical calculations.     

Fission dynamics of the compound nucleus 213Fr formed in heavy-ion-induced reactions

A stochastic approach based on one-dimensional Langevin equations was used to calculate the average pre-fission multiplicities of neutrons, light charged particles and the fission probabilities for the compound nucleus ²¹³Fr and the results are compared with the experimental data. In these calculations, a modified wall and window dissipation with a reduction coefficient, k _s , has been used in the Langevin equations. It was shown that the results of the calculations are in good agreement with the experimental data by using values of k _s in the range 0.3?≤?k _s ?≤?0.5.     

Vibronic coupling in the first four electronic states of CH2F+2

Vibronic coupling in the energetically lowest first four electronic states of CH₂F⁺₂ is studied in this paper. A model 4×4 Hamiltonian is constructed in a diabatic electronic representation employing normal coordinates of vibrational modes and standard vibronic coupling theory. Extensive ab initio quantum chemistry calculations are carried out to determine the parameters of the Hamiltonian and energetic ordering of the electronic states. The topographical features of the latter are examined at length and several conical intersections are established. Nuclear dynamics calculations on coupled electronic states are carried out from first principles by propagating wave packet. Theoretically calculated broad band vibronic structure of the four states are found to be in good accord with the experimental results.     

ErklÄrung der charakteristischen Eigenschaften experimenteller Backbending-Kurven und neue Ergebnisse für Energien undB(E2)-Werte im Rahmen des Teilchen-Rotor-Modells

At first the fundamental properties of our simple model for backbending-nuclei are discussed and it is shown that the underlying band-structures are responsible for the characteristic features of the experimental backbending-curves. Then a comparison between the results of new calculations in the particle-rotor-model with VMI-core and the experimental data for the yrast-bands of 15 nuclei between¹²⁶Ba and¹⁸⁶Os is performed yielding very good agreement between theory and experiment. The remaining discrepancies for highJ-values can be removed by a modification of the VMI-core, as it is exemplarily shown in the case of¹⁶⁴Yb. Applying our model to¹⁶⁴Er, where some members of the second band recently have been found, the experimental energies of the yrast- and of the second band can be reproduced nearly quantitatively without introducing new parameters. At last theB(E2)-values for transitions in the yrast-band are calculated. Recent experimental data for the Ce-isotopes are compared with the results of our calculations and, except for¹³²Ce, good agreement is obtained.     

Structural,electronic and optical properties of cubic SrTiO3 and KTaO3: Ab initio and GW calculations

We present first-principles VASP calculations of the structural, electronic, vibrational, and optical properties of paraelectric SrTiO₃ and KTaO₃. The ab initio calculations are performed in the framework of density functional theory with different exchange-correlation potentials. Our calculated lattice parameters, elastic constants, and vibrational frequencies are found to be in good agreement with the available experimental values. Then, the bandstructures are calculated with the GW approximation, and the corresponding band gap is used to obtain the optical properties of SrTiO₃ and KTaO₃.     

The electronic structure and magnetic properties of metallic antiferromagnetic Co[(CH3PO3)(H2O)] studied by first-principles calculations

The electronic structure, the metallic and magnetic properties of metal phosphonate Co[(CH₃PO₃)(H₂O)] have been studied by first-principles calculations, which were based on the density-functional theory (DFT) and the full potential linearized augmented plane wave (FPLAPW) method. The total energy, the spin magnetic moments and the density of the states (DOS) were all calculated. The calculations reveal that the compound Co[(CH₃PO₃)(H₂O)] has a stable metallic antiferromagnetic (AFM) ground state and a half-metallic ferromagnetic (FM) metastable state. Based on the spin distribution obtained from calculations, it is found that the spin magnetic moment of the compound is mainly from the Co²⁺, with some small contributions from the oxygen, carbon and phosphorus atoms, and the spin magnetic moment per molecule is 5.000μ_B, which is in good agreement with the experimental results.     

Two-photon vibronic spectroscopy of allene at 7.0–10.5 eV: experiment and theory

2?+?1 resonance-enhanced multiphoton ionization (REMPI) spectra of allene at 7.0–10.5?eV have been observed. The excited vibronic symmetry has been determined from polarization-ratio measurements. Based on the vibronic energies and peak intensities calculated using ab initio MO and time-dependent density functional theory, the very congested REMPI spectra have been assigned as due to π*?←?π, 3p?←?π, 4s?←?π, 4p?←?π, and 4d?←?π transitions. Vibrational progressions related to the CH₂ twisting (ν₄ ～770?cm^?1) have been observed for several excited electronic states. Calculated Franck–Condon factors also confirm that CH₂ twisting is the most active mode in the vibronic spectra of allene. In this study, theoretical calculations of two-photon intensities and polarization ratios have been made through the ab initio computed one-photon transition dipole moments to various electronic states as intermediates. As a starting point to interpret the complicated vibronic spectrum of allene, the theoretical approach, without vibronic couplings, has been applied to predict the peak positions, spectral intensities, and polarization ratios of Rydberg states, and qualitatively shows a considerable agreement with experimental observations.     

Two-phonon Raman spectra of LiH and LiD crystals

The experimental two-phonon Raman spectra of LiD and LiH are reported here. A deformation dipole model formulated elsewhere for LiD is used to compute the lattice dynamics of LiD and LiH required in the Raman intensity calculations. The use of the same model for LiH is justified by the good agreement between the peak positions of the temperature-weighted two-phonon density of states and the various experimental spectra. The Raman intensity calculations are carried out by treating the second-order expansion coefficients in the polarisability tensor as adjustable parameters. The need for the parameters associated with the next-nearest-neighbor ions is clearly demonstrated for all the spectra. A single set of six parameters for the T₂₈ spectra and thirteen parameters for the E₈ (or A₁₈) spectra is found to explain all the experimental spectra of LiD and LiH quite well. Since the polarisability of Li⁺ is very small, the need for the second-neighbor positive-positive parameters reflects on the extended and highly polarisable nature of the H^? or D^? ion.     

Fission characteristics of 216Ra formed in heavy-ion induced reactions

A Kramers-modified statistical model is used to calculate the cross-section of the evaporation residue, fission cross-section, average pre-fission multiplicities of protons and α-particles for ²¹⁶Ra formed in ¹⁹F+?¹⁹⁷Au reactions and results are compared with the experimental data. To calculate these quantities, the effects of temperature and spin K about the symmetry axis have been considered in the calculations of the potential energy surfaces and the fission widths. It is shown that the results of the calculations using values of the temperature coefficient of the effective potential k?=?0.008±0.003 MeV^???2 and scaling factor of the fission-barrier height r _s?=?1.004±0.002 are in good agreement with the experimental data.     

Lattice dynamics of ZnSe x S1 − x semiconductor crystals

Recently ultrabroadband infrared solid state lasers based on a new vibronic material Cr²⁺:ZnSe _x S_1–x were demonstrated [1–3]. Cr²⁺ ion substitutes the metal ion (tetrahedral sites), the crystal field of the solid solution is responsible for large inhomogeneous broadening of Cr²⁺ electron states. The crystal field can be reconstructed by investigation of lattice dynamics — optical phonon parameters and dielectric function in IR. We paid special attention to investigation of vibrational and infrared spectroscopic properties of ZnSe _x S_{1 ? x} crystals. A very interesting and somewhat unexpected result of these studies was the existence in the crystals of effective S-Se dipoles, which generate an additional deep dynamically charged level in the forbidden gap of the semiconductors. The results of the first-principles calculations of both the phonon structure and the electron localization in ZnSe _x S_1–x crystals as well as acceptor levels in Cr²⁺: ZnSe crystal are discussed.     

An investigation of range distribution parameters of implanted 19F ions in Au,Ag and Cu noble metals

Depth profiles of fluorine implanted in gold, silver and copper metal have been accurately measured using the ¹⁹F(p,αγ)¹⁶O resonance nuclear reaction at E_R = 872.1 keV. A proper deconvolution calculation method was used to extract the depth profile of fluorine from the experimental excitation yield curves. The range parameters, R_p, ΔR_p, and SK obtained in this work were compared with the theoretical calculations. The comparison shows that for all materials studied here the experimental R_p values are in good agreement with the results obtained by the TRIM96 code, while the experimental range stragglings, ΔR_p, are systematically larger than the TRIM simulation results.     

Non-normal parity states in mass 10–15 nuclei

The modified surface delta interaction (MSDI) is used as the effective two-nucleon residual interaction in extensive shell-model calculations forA=10–15 nuclei; a He-4 core andj-j coupled extra-core nucleon configurations of the formP _3/2 ⁿ P _1/2 ^m (1d _5/2,2s _1/2)¹ are employed. Level energies and wave functions for low-lying non-normal parity states are first obtained from a simultaneous fit to experimental energies over the entire 10–15 mass range. The wave functions are next tested by comparing predicted nuclear properties with experimental data: single-nucleon spectroscopic factors, beta decay lifetimes,M1 andE2 radiative transition widths as well asE1 andM2 radiative widths are calculated. In general good agreement between experiment and theory is obtained.     

Absorption and resonance Raman spectroscopy of the 1Bu state of trans‐1,3,5‐hexatriene including vibronic coupling

The vibronic coupling between the first excited S₁ (2¹A_g) and the second excited S₂ (1¹B_u) singlet electronic states in spectroscopy of trans‐1,3,5‐hexatriene molecule is investigated on the basis of a model consisting of two electronic states coupled by two vibrational modes. Employing a perturbation theory that treats the intramolecular couplings in a perturbative manner, the absorption and resonance Raman cross sections and excitation profiles of this molecule are calculated using the time‐correlation function formalism. The non‐Condon corrections are included in evaluation of cross sections. The multidimensional time‐domain integrals that arise in these calculations have been evaluated for the case in which S₀ (1¹A_g) S₂ (1¹B_u) electronic transition takes place between displaced and distorted harmonic potential energy surfaces. The calculated spectra are in good agreement with the experimental ones. Copyright © 2011 John Wiley & Sons, Ltd.