Effective collision strengths among the fifteen lowest states of FeXVII

Collision strengths have been calculated for electron impact excitation of neon-like Fe XVII for all transitions within its 15 lowest states. Configuration interaction wavefunctions have been used to represent the target states. The standardR-matrix code has been used to calculate the contribution from the lower scattering partial waves (L⩽9), while the no exchange version of the same code has been used to compute efficiently the contribution of higher partial waves (L⩾10). Effective collision strengths for all the 105 transitions are tabulated for elected temperatures in the range logT _e=5.40 to logT _e=7.00 withT _e expressed in °K.     

Electron impact excitation of Ni XIX using theR-matrix method

Collision strengths for all the transitions between the 15 lowest states of neon-like Ni XIX have been calculated for electron impact in the 80–140 Ry energy range. Configuration-interaction wavefunctions have been used to represent the target states. The standardR-matrix code has been used to calculate the lower scattering partial waves (L≤9), while a no-exchange version of the same code has been used to compute efficiently the higher partial waves (L≥10). Effective collision strengths for 105 excitation transitions between the ground state 2s ²2p ^{6 1} S ^e and the 142s ²2p ⁵3l Rydberg states are tabulated for electron temperatures in the range logT=5.40 to logT=7.00, withT expressed in °K.     

The collective bands of positive parity states in odd-A (fp) shell nuclei

The low-lying collective bands of positive parity states in (fp) shell nuclei are described in the deformed Hartree-Fock method by projecting states of definite angular momenta from ‘the lowest energy intrinsic states in (sd)⁻¹ (fp) ⁿ⁺¹ configurations. The modified Kuo-Brown effective interaction for (fp) shell and modified surface delta interaction (MSDI) for a hole in (sd) shell with a particle in (fp) shell have been used. The collective bands of states are in general well reproduced by the effective interactions. The excitation energies of the band head states are however off by about one MeV. The calculated magnetic moments of the band headj=3/2⁺ states are in reasonable agreement with experiment. Using effective chargese _p=1.33e ande _n=0.64e we get fairly good agreement forE(2) transitions. The hinderedM(1) transition strengths are reproduced to the correct order however they are slightly higher compared to experiment.     

Directed polymers in a random environment: Some results on fluctuations

We consider a polymer model on ℤ ₊ ^d where to each edgee is associated a random variable v(e). A polymer configuration is represented by a directed pathr and has a weight exp[-β ∑ _e ∈r ν(e)], withβ=1/T the inverse temperature. We extend some rigorous results that have been obtained for the ground state of this model to finite temperatures. In particular we obtain some upper and lower bounds on sample-to-sample free energy fluctuations, and also rigorous scaling inequalities between the exponents describing free energy fluctuations and transversal displacements of polymer configurations     

Electron collisional excitation of argon-like Ni XI using the Breit-Pauli R-matrix method

Electron excitation collision strengths for the transitions from the ground state to the fine-structure levels of the 3s²3p⁵3d and 3s²3p⁶3d configurations in Ni XI are calculated using the Breit-Pauli R-matrix method. Configuration interaction wavefunctions have been used to represent the target states. The relativistic effects are incorporated in the Breit-Pauli approximation by including one-body mass correction, Darwin, and spin-orbit interaction terms in the scattering equations. Collision strengths are tabulated at selected energies in the range 10 to 75 Rydberg. Effective collision strengths are determined by integrating collision strengths by assuming a Maxwellian distribution of electron energies. The effective collision strengths are listed over a wide temperature range (2×10⁴-1×10⁷ K) applicable to astrophysical plasmas. Our results are the only collision strengths and effective collision strengths available for this ion. We believe that the data calculated in this work will be useful in solar, astrophysical and laser applications.     

7Li2分子23Πu激发态的解析势能函数、振动能级及其转动惯量

使用Gaussian 03程序包中的“对称性匹配簇-组态相互作用”方法、在0.13—2.0nm的核间距范围内利用6-311+〖KG-*3〗+G(d,p)基组对⁷Li₂(2³Π_u)分子的势能曲线进行了计算, 同时使用最小二乘法将计算结果拟合成了解析势能函数. 利用拟合出的解析势能函数并结合Rydberg-Klein-Rees方法, 计算了该态的谐振频率, 进而计算了该态的其他光谱常数, 分别为T关键词： 解析势能函数 谐振频率 振动能级 转动惯量     

Collisional-radiative volume recombination and ionization coefficients for quasi-stationary helium plasmas

Collisional-radiative recombination and ionization coefficients, α andS, have been calculated on the basis of a non-hydrogen-like collisional-radiative model for atomic helium. The singlet and triplet systems have been considered as two individual systems coupled to each other through a set of elementary processes for collisions and radiation. Auto-ionization states have not been taken into account. Therefore the computations of the coefficient α have been limited to the range 125≦T _e [°K]≦64000. (AboveT _e=64 000 °K the auto-ionizing states considerably influence the recombination rates (di-electronic recombination).) The results show that the α- andS-coefficients for helium are more sensitive to radiative trapping than those for hydrogen under comparable absorption conditions. Concerning the α-values: For low electron densities one obtains approximately α_helium≈2α_hydrogen, whereas at high electron densities one finds approximately α_helium≈1/2α_hydrogen (to 1/10 α_hydrogen at high electron temperatures). Collisional-radiative ionization coefficients for atomic helium have not yet been published in the past. In the present paper one finds for the first time a complete set ofS-coefficients for different degrees of radiative trapping.     

CO2-laser gas discharges in narrow gaps

We have studied RF discharges as excitation mechanisms for distributed feedback (DFB) CO₂ lasers. For CO₂ laser plasmas the reduced electric fieldE/N has to be in a well-defined range. The reduced electric fieldsE/N of gas discharges in the narrow gaps with widths of the order of 100 m required for DFB are considerably above this range. In order to study the feasibility of these RF-excited discharges for DFB CO₂ lasers we have measured the electron temperatureT _e in their plasmas. From helium-line-intensity ratios we have deduced a lower limit of the electron temperatureT _e of 4eV. The observed high intensities of bands of singly ionized nitrogen indicate an even higher electron temperature, but an efficient pumping of the upper laser level is not possible with an electron temperature above 2.5 eV.We have estimated the electron densityn _e and the current densityj _e from ratios of the intesities of forbidden and allowed helium lines. The high current densityj _e is in the range of abnormal glow discharges.In the gas discharges between narrow gaps the electron oscillation amplitudex _e is large than the electrode separationd. In order to replace the resulting high electron losses a high electron temperatureT _e is necessary to sustain the gas discharge. Because of this high electron temperatureT _e an efficient pumping of the upper laser level is not possible.     

Measured mixer noise temperature and conversion loss of a cryogenic Schottky diode mixer near 800 GHz

We accurately measured the noise temperature and conversion loss of a cryogenically cooled Schottky diode operating near 800 GHz, using the UCB/MPE Submillimeter Receiver at the James Clerk Maxwell Telescope. The receiver temperature was in the range of the best we now routinely measure, 3150 K (DSB). Without correcting for optical loss or IF mismatch, the raw measurements set upper limits ofT _M=2850 K andL _M=9.1 dB (DSB), constant over at least a 1 GHz IF band centered at 6.4 GHz with an LO frequency of 803 GHz. Correction for estimated optical coupling and mismatch effects yieldsT _M=1600 K andL _M=5.5 dB (DSB) for the mixer diode itself. These values indicate that our receiver noise temperature is dominated by the corner cube antenna's optical efficiency and by mixer noise, but not by conversion loss or IF mismatch. The small fractional IF bandwidth, measured mixer IF band flatness from 2 to 8 GHz, and similarly good receiver temperatures at other IF frequencies imply that these values are representative over a range of frequencies near 800 GHz.     

Superconductivity in ultrathin films I. Transition temperatures of amorphous Bi and Ga

Superconducting transition temperatures (T _c) and electron tunneling characteristics have been measured on amorphous, vapour quenched films of Ga and Bi in the thickness range 3 to 50 nm. TheT _c's are depressed and the tunnel densities of states are smeared as compared to bulk superconductors. A model considering the proximity effect between an extremely thin non-superconducting sheath (presumably due to the decrease of electron concentration at the surfaces) and a remaining bulk superconducting part gives good agreement withT _c measurements, while the predicted tunnel density of states is only in qualitative correspondence with experiments.     

双温度氦等离子体输运性质计算

获得覆盖较宽温度和压力范围内的等离子体输运性质是进行等离子体传热和流动过程数值模拟的必要条件.本文采用Saha方程计算等离子体组分, 采用基于将Chapman-Enskog方法扩展到高阶近似的方法, 计算获得了电子温度(T_e)不等于重粒子温度(T_h)的情形下, 在300 K到40000 K的温度范围内氦等离子体的黏性、热导率和电导率. 研究结果表明压力和热力学非平衡参数(θ =T_e/T_h)对氦等离子体的输运性质有较大的影响. 在局域热力学平衡条件下,计算获得的氦等离子体输运性质和文献报道的数据符合良好.     

Molecular field effects in Mössbauer spectra of FeSb2O4

Mössbauer effect measurements have been made using⁵⁷Fe in FeSb₂O₄. At liquid helium temperature a combined electric quadrupole and magnetic hyperfine interaction is observed withH _eff=185±2 kOe, 1/2e ² qQ=2.94±0.09 mm/sec and =0.37±0.09. The direction ofH _eff is perpendicular to thec axis of the crystal and at 33° to the <110> direction. Thec axis is determined to be the direction of the intermediate principal EFG tensor axis. Calculations are made using a molecular field term in the Hamiltonian for the Fe²⁺ orbitals. The results of these calculations are used to explain the observed values of 1/2e ² qQ and and permit a determination of the ordring of the T_2g orbitals among the T_2g energy levels.     

Wei Hua’s four-parameter potential: Comments and computation of molecular constants αe and εeXe

The value of adjustable parameterC in the four-parameter potentialU(r) =D _e [(1 - exp[-b(r -r _e)])/(1 -C exp[-b(r -r _e)])]² has been expressed in terms of molecular parameters and its significance has been brought out. The potential so constructed, withC derived from the molecular parameters, has been applied to ten electronic states in addition to the states studied by Wei Hua. Average mean deviation for these 25 states has been found to be 3.47 as compared to 6.93, 6.95 and 9.72 obtained from Levine, Varshni and Morse potentials, respectively. Also Dunham’s method has been used to express rotation-vibration interaction constant (α_e) and anharmonicity constant (ω_ex_e) in terms ofC and other molecular constants. These relations have been employed to determine these quantities for 37 electronic states. For α_e, the average mean deviation is 7.2% compared to 19.7% for Lippincott’s potential which is known to be the best to predict these values. Average mean deviation for (ω_ex_e) turns out to be 17.4% which is almost the same as found from Lippincott’s potential function.     

Multireference CI calculations of radiative transition probabilities between low lying quartet states of the C2+ ion

Potential energy functions for the ten lowest electronic states of the C₂⁺ ion have been calculated from correlated CASSCF and MC-CI electronic wavefunctions and used for derivation of the spectroscopic constants. The predicted values are expected to be accurate within 0.01 Å for R_e, 20–30 cm⁻¹ for ω_e and 0.05–0.1 eV for T_e. For the three lowest quartet states the electronic transition moment functions have also been calculated. For the transitions among these states, radiative lifetimes and absorption oscillator strengths are given which should be accurate within about 15%.     

Hyperfine interaction of111Cd in antiferromagnetic cobalt oxide

The temperature dependence of the hyperfine field of substitutional¹¹¹Cd in antiferromagnetic CoO has been measured by means of the perturbed angular correlation technique. The Larmor frequency ω_L is found to obey a power law ω_L(t=ω₀ t ^β) up tot _max=0.4 wheret=1−T/T _N is the reduced temperature withT _N=291.2(3) K and β=0.393 (5) the critical exponent. The results are discussed and compared with PAC experiments on¹¹¹Cd in NiO and Ni and with results obtained by other methods.     

Electronic thermal capacity in one-dimensional mesoscopic rings

Summary We have investigated the Aharonov-Bohm (AB) effects of electronic thermal capacityC _v in a one-dimensional normal ring using the free-electron model. The results show that the thermal capacity is an oscillation function of external magnetic flux with periods ϕ₀=hc/e, ϕ₀/2, ϕ₀/3,... The amplitude of the capacity fluctuation decreases when temperature increases forT>3T ^* (T ^*=ħ V _F/(K _BπL)). We suggest an appropriate temperatureT∼3T ^* to observe in experiment the capacity-flux characteristic for metallic rings. The authors of this paper have agreed to not receive the proofs for correction.     

Polar optical phonon limited energy and momentum relaxation of hot electrons in a GaAs-quantum well (QW)

The average energy loss rate, the energy- as well as the momentum relaxation time of hot electrons confined in a GaAs-square quantum well are calculated as a function of the external controllable parametersn _s (electron density),T (lattice temperature) andT _e (electron temperature) for the interaction of the charge carriers with bulk- and surface polar optical phonons. Analytical expressions are derived in the limit of vanishing quantum well width at non-degeneracy and degeneracy of the electron system. Both energy-and momentum relaxation time are found to be complicated functions of the ratiosT _D /T _e andT _D /T withT _D being the Debye-temperature of the polar optical phonon involved in the scattering. In a thick (very thin) QW the energy loss rate to bulk PO-phonons is found to be larger (smaller) than the corresponding loss rate to surface modes. The energy- (momentum-) relaxation times are found to be constant (increasing) functions ofn _s at non-degeneracy (degeneracy) of the electron system. Dedicated to Professor Karlheinz Seeger on the occasion of his 60th birthday     

Ab initio investigation of the electronic and vibrational properties for the (CaLi)+ ionic molecule

A wide adiabatic study has been performed for numerous electronic states of CaLi⁺ molecular ion. The adiabatic potential energy curves and their spectroscopic constants (R_e, D_e, ω_e and T_e) have been calculated using an ab initio approach including a nonempirical pseudo-potential for the Ca and Li cores with the core polarisation potentials operator through full configuration interaction (FCI). Thereafter, the energies of vibrational levels and their spacing for all these states have been reported. In addition, the electric dipole moment curves have been investigated for the (1-19) Σ, (1-12) Π and (1-8) Δ electric states. Moreover it lets us check the extreme transition dipole moments (TDM). These behaviours of TDM are more accustomed to estimate the radiative lifetimes for all vibrational levels in 2¹Σ⁺ and 3¹Σ⁺ states. Also, the bound-bound and the bound-free contribution have been calculated precisely and by employing a Franck–Condon (FC) approximation.     

Ultra-low temperature study of the even-denominator FQHE state

We present experimental data showing unambiguously an even-denominator fractional quantum Hall effect (FQHE) state at . At a bath temperature T_b=8 mK, we observe a Hall plateau quantized to a value of 2h/5e² with an uncertainty smaller than 2 parts in 10⁶ and a vanishing R_xx (R_xx=1.7±1.7 Ω). The thermal activation energy gaps Δ at Landau level filling factors , and are 0.11, 0.10, and 0.055 K, respectively. Adding a disorder broadening (typically 2 K) to these values, we deduce that all three FQHE states have probably very similar energy gaps. The electron heating experiment shows that the 2D electrons are efficiently cooled to the bath temperature for T_b8 mK. We also explore the density dependence of the activation gap at . Preliminary results at T_b25 mK show that the state is very sensitive to disorder.     

Anomalous Electric Fields Inside a Dense Plasma of a Current Sheet

For the first time there have been analyzed profiles of electric-field-sensitive n_a spectral lines of the Li-like impurity ions CIV, NV, OVI emitted by a hot dense plasma of a plane current sheet. Theoretical profiles of these lines have been calculated with an allowance for Anomalous Electric Fields (AEF). By comparing the experimental and theoretical profiles of the lines it has been established for the first time that in the plane current sheet there were developed AEF of rms strengths F₀ ≈ (100–120) kV/cm in the time interval from τ = ?0.2 μs to τ = 0 (the time τ was counted from the instant of the maximum intensity of the spectral line OVI 5291 Å). These results have been backed up by a similar analysis of the experimental profiles of the spectral line HeII 4686 Å of the primary gas of the discharge. The AEF reached these strengths at the same instant of time, τ = ?0.2 μs, when electron and ion temperatures reached their maxima: T_e ? 100 eV, T_i ≈ 300 eV. The instant τ = ?0.2 μs corresponds to a transition from the metastable stage to the explosive phase of the current sheet evolution. At this time the ratio of the AEF energy density to the thermal energy density of the plasma was § ≡ F²₀/[8π/N_eT_e + N_iT_i)] ≈ 10^?3, which exceeded a similar ratio for the thermal wave field by three orders of magnitude.