Observation of the v = 0–13 levels of Na2b3Πu by OODR 3Λg-b3Πu fluorescence spectroscopy

The absolute vibrational numbering of the Na₂b³Π_u state has been established by direct observation of the v = 0–13 levels. These b³Π_u levels appear as the lower levels in rotationally resolved fluorescence spectra resulting from OODR excitation of ³Π_g, ³Δ_g, and ³Σ_g⁺ states via b³Π_u ～ A¹Σ_u⁺ mixed intermediate levels. The molecular constants for the Na₂b³Π_u state are (in cm^?1, one standard error in parentheses)

     

2.

The CΠ_u state of Na₂ revisited: A comprehensive study by polarization labeling spectroscopy technique     

A. Grochola  P. Kowalczyk 《Journal of Molecular Spectroscopy》2005,232(2):291-295

This paper contains the analysis of the C(2)¹Π_u state of Na₂ molecule based on a large data set (3030 lines) obtained from a polarization labeling spectroscopy experiment on the transition. The energies of rovibrational levels in the C state, spanning a wide range of v (0 ? v ? 43) and J (12 ? J ? 100) quantum numbers, are fitted to a Dunham polynomial expansion and also to a numerical potential curve constructed by the inverted perturbation approach (IPA) method.     

3.

Co-L₃ X-ray absorption near-edge structure analysis of Pr_1−xCa_xCoO_3−δ and Pr_1−xSr_xCoO_3−δ     

Tsuyoshi Yoshioka  Tomoyuki Yamamoto  Akihiko Kitada 《Physica B: Condensed Matter》2012,407(21):4114-4116

The valence state of Co ions in Pr_1−xCa_xCoO_3−δ and Pr_1−xSr_xCoO_3−δ has been investigated by an analysis of the Co-L₃ X-ray absorption near-edge structure (XANES) profile. The observed intensity distributions of Co-L₃ XANES change continuously with increasing concentration of alkaline-earth ions. To investigate the origin of this change in the XANES profile, charge transfer multiplet calculations were carried out, which could successfully explain the change in the spectral profile; they also suggest that the valence state of Co ions in Pr_1−xCa_xCoO_3−δ and Pr_1−xSr_xCoO_3−δ is between 3+ and 4+ and increases gradually with the concentration of alkaline-earth ions.     

4.

Exact P_sT_d invariant and P_sT_d symmetric breaking solutions,symmetry reductions and Bäcklund transformations for an AB–KdV system     

Man Jia  Sen Yue Lou 《Physics letters. A》2018,382(17):1157-1166

In natural and social science, many events happened at different space–times may be closely correlated. Two events, A (Alice) and B (Bob) are defined as correlated if one event is determined by another, say, $B=\stackrel{?}{f}A$ for suitable $\stackrel{?}{f}$ operators. A nonlocal AB–KdV system with shifted-parity ($P_s$, parity with a shift), delayed time reversal ($T_d$, time reversal with a delay) symmetry where $B=\stackrel{?}{P_s}\stackrel{?}{T_d}A$ is constructed directly from the normal KdV equation to describe two-area physical event. The exact solutions of the AB–KdV system, including $P_s{T}_d$ invariant and $P_s{T}_d$ symmetric breaking solutions are shown by different methods. The $P_s{T}_d$ invariant solution show that the event happened at A will happen also at B. These solutions, such as single soliton solutions, infinitely many singular soliton solutions, soliton–cnoidal wave interaction solutions, and symmetry reduction solutions etc., show the AB–KdV system possesses rich structures. Also, a special Bäcklund transformation related to residual symmetry is presented via the localization of the residual symmetry to find interaction solutions between the solitons and other types of the AB–KdV system.     

5.

Structure and magnetism in Ho_1−xSr_xCoO_3−δ     

D.J. Goossens  K.F. Wilson 《Journal of Physics and Chemistry of Solids》2005,66(1):169-175

We have magnetically and structurally characterized the Ho_1−xSr_xCoO_3−δ family of materials where 0.67≤x≤0.95. The solid solution range and evolution of the structure as a function of x is established and correlated with the broad range of magnetic behavior observed. The structure is shown to be tetragonal I4/mmm although is possibly cubic when x=0.95. For 0.67≤x≤0.9 the material shows antiferromagnetic long range order and ferromagnetic clusters. At x=0.95 the magnetic transition is at 120 K and the imaginary susceptibility becomes non-zero and the temperature of the cusp in the ac susceptibility shows a frequency dependence indicative of glassiness.     

6.

Structural and superconductivity study on α-FeSe_x     

Zhaofei Li  Jun Tang  Masanori Watahiki 《Journal of Physics and Chemistry of Solids》2010,71(4):495-1635

We have successfully synthesized the α-FeSe_x binary tetragonal superconductors with nominal composition of FeSe_x (x=0.6-1.0) via conventional solid state reactions between Fe and Se sealed in quartz tubes. Fe and β-FeSe are the most commonly seen impurities in this binary system. A low-temperature annealing at 400 °C is found to be crucial to remove β-FeSe, which is the thermodynamic stable phase with hexagonal symmetry. For all the samples of FeSe_x, superconductivity is confirmed by magnetic measurements as well as resistivity measurements with their T_c at around 8 K. We noticed that their T_c does not vary with the different nominal Se amount. High-resolution synchrotron X-ray diffraction analysis revealed that the unit cell parameters of all these samples do not change within the error range, and their structure only tolerate the same very small amount of Se deficiency. Based on this study, we concluded that the α-FeSe_x superconductor only exist in a very narrow deficiency range.     

7.

TE_1n /TM_1n激励圆锥喇叭辐射功率测量方法     

袁成卫  彭升人  张强 《强激光与粒子束》2016,28(8):083005

研究了TE1n /TM1n模式激励的圆形口径喇叭天线的辐射场特征,导出了根据辐射场计算天线辐射总功率的方法:通过测定天线E面和H面的辐射场功率密度分布,分别进行球冠积分,其平均值即为天线的辐射总功率;并进行了数值仿真验证。分析了测量角度范围和测量点数目对测量功率的影响,提出了通过数据拟合来降低测量误差的一种方法;给出了测量角度范围和测量点数的选取原则,功率测量可在15 dB或18 dB波束宽度范围内进行,测量点数一般选15个左右。     

8.

Ar⁺ laser-induced fluorescence spectra of Cs₂: The E¹Σ_u⁺ and (1) ¹Π_g electronic states     

C. Amiot  C. Crépin  J. Vergès 《Journal of Molecular Spectroscopy》1984,107(1):28-47

Laser-induced fluorescence of Cs₂ molecules in the infrared (1.15–2.5 μm) and the visible (505–545 nm) regions has been observed using several excitation wavelengths from an argonion laser. Accurate molecular constants and potential energy curves for the pumped E¹Σ_u⁺ state and the first excited gerade ¹Π state are derived from more than 1300 fluorescence lines precisely measured with a high-resolution Fourier transform interferometer. The main molecular constants for the states are

$\text{T}{}_{\mathrm{e}}$	13 517.2 (1.3)	$\text{B}{}_{\mathrm{e}}$	0.1434 (0.0027)
$\text{ω}{}_{\mathrm{e}}$	153.6 (1.1)	$\text{α}{}_{\mathrm{e}}$	9×10?5 (4×10?4)
$\text{ω}{}_{\mathrm{e}}\text{ξ}{}_{\mathrm{e}}$	0.47 (0.09)	$\text{r}{}_{\mathrm{e}}$	3.20 (0.03) Å
$\text{A}{}_{\mathrm{e}}$	7.85 (0.60)	$\text{α}{}_{\mathrm{A}}$	0.19 (0.16)

     

9.

Electrical conductivity and structural stability of SrCo_1−xFe_xO_3−δ     

Zhifeng Wang  Nansheng Xu  Weizhong Ding  Fushen Li 《Journal of Physics and Chemistry of Solids》2011,72(1):50-55

Perovskite compounds in the system of SrCo_1−xFe_xO_3−δ (x=0.2, 0.4 and 0.6) were synthesized by solid state reaction. SrCo_1−xFe_xO_3−δ shows the p-type small polaron conduction behavior. Electrical conductivity and oxygen vacancy content decrease with increase in Fe content. The incorporation of Fe increases the structural stability of SrCo_1−xFe_xO_3−δ at low temperatures, while decreasing the structural stability at high temperatures. Oxygen partial pressure has a strong influence on electrical conductivity. At low oxygen partial pressure, SrCo_0.8Fe_0.2O_3−δ will transform from cubic to orthorhombic structure. This structure can remain in 5%H₂/Ar only for a short time and then dissociates into Sr₃Fe₂O_6.64 and Co due to the reduction of B-site elements.     

10.

Mixed electrical conduction in Ce_1−xCa_xO_2−x     

M.D. Hurley  D.K. Hohnke 《Journal of Physics and Chemistry of Solids》1980,41(12):1349-1353

The solid electrolyte Ce_1?xCa_xO_2-?x with the fluorite-type structure (Ca-doped CeO₂) is a mixed conductor. Conduction occurs predominantly by migration of O^2? ions via oxygen vacancies or by electrons, depending on the departure from stoichiometry. The ionic transference number σ_i/σ_i + σ_e was determined as a function of dopant concentration (0.07?x?0.15), temperature (400–800°C), and oxygen pressure by emf measurements with oxygen concentration cells. It is described by

The entropy term S¹(x) changes from 38.7k for x = 0.07 to 31.7k for x = 0.15; the enthalpy term, 5.42 eV, is independent of x and in excellent accord with semi-empirical calculations.     

11.

Structural and electronic properties of zinc blende B_xAl_1−xN_yP_1−y quaternary alloys via ?rst-principle calculations     

A. Abdiche  R. BaghdadR. Khenata  R. RianeY. Al-Douri  M. GuemouS. Bin-Omran 《Physica B: Condensed Matter》2012,407(3):426-432

The structural and electronic properties of cubic zinc blende BN, BP, AlN and AlP compounds and their B_xAl_1−xN_yP_1−y quaternary alloys, have been calculated using the non relativistic full-potential linearized-augmented plane wave FP-LAPW method. The exchange-correlation potential is treated with the local density approximation of Perdew and Wang (LDA-PW) as well as the generalized gradient approximation (GGA) of Perdew-Burke and Ernzerhof (GGA-PBE). The calculated structural properties of BN, BP, AlN and AlP compounds are in good agreement with the available experimental and theoretical data. A nonlinear variation of compositions x and y with the lattice constants, bulk modulus, direct and indirect band gaps is found. The calculated bowing of the fundamental band gaps is in good agreement with the available experimental and theoretical value. To our knowledge this is the first quantitative theoretical investigation on B_xAl_1−xN_yP_1−y quaternary alloy and still awaits experimental confirmations.     

12.

High temperature transport and thermoelectric properties of Ca_3−xEr_xCo₄O_9+δ     

J. PeiG. Chen  N. ZhouD.Q. Lu  F. Xiao 《Physica B: Condensed Matter》2011,406(3):571-574

Ca_3−xEr_xCo₄O_9+δ (x=0, 0.05, 0.15, 0.3 and 0.5) samples were prepared using a sol-gel method followed by hot-pressing sintering technique. Powder X-ray diffraction analysis showed the single-phases of Ca_3−xEr_xCo₄O_9+δ were obtained up to x=0.3 and the crystallinity of the samples decreased with increasing Er-doping amount. The high-temperature (323-1073 K) thermoelectric properties of the samples were investigated. The substitution of Er³⁺ for Ca²⁺ resulted in the decrease of electrical conductivity, thermal conductivity and the increase of Seebeck coefficient for all the samples except the x=0.05 one. The dimensionless figure of merit ZT reached 0.28 at 1073 K for Ca_2.7Er_0.3Co₄O_9+δ, indicating the thermoelectric properties of CaCo₄O_9+δ can be enhanced by doping Er in the system.     

13.

Nanocomposite L1₀ FePt–SiN_x and FePt–SiN_x–C films with large coercivity and small grain size on a TiN intermediate layer     

K.F. Dong  H.H. Li  Y.G. Peng  G. Ju  G.M. Chow  J.S. Chen 《Journal of magnetism and magnetic materials》2012

FePt–SiN_x–C films with high coercivity, (001) texture and small grain size were obtained by co-sputtering FePt, Si₃N₄ and C on TiN/CrRu/glass substrate at 380 °C. Without C doping, FePt–SiN_x films with good perpendicular anisotropy and a single layer structure were obtained. However, the grain size was still too large and the grain isolation was poor. When C was doped into the FePt–SiN_x films, the out-of-plane coercivity increased due to the decrease of the exchange coupling. In addition, the grain size of the FePt films decreased, and well-separated FePt grains with uniform size were formed. The microstructure of [FePt–SiN_x 40 vol%]−20 vol% C films changed from a single layer structure to a multiple layer structure when the FePt thickness was increased from 4 to 10 nm. By optimizing the sputtering process, the [FePt (4 nm)–SiN_x 40 vol%]−20 vol% C (001) film with coercivity higher than 21.5 kOe, a single layer structure, and small average FePt grain size of 5.6 nm was obtained, which makes it suitable for ultrahigh density perpendicular recording.     

14.

High resolution rovibrational spectroscopy of pyrimidine: Analysis of the B₁ modes ν_10b and ν₄ and B₂ mode ν_6b     

Sieghard Albert  Martin Quack 《Journal of Molecular Spectroscopy》2007,243(2):280-291

We report the first high resolution rovibrational analysis of the infrared spectrum of pyrimidine (C₄H₄N₂) based on measurements using our Fourier transform spectrometer, the Bruker IFS 125 HR Zürich Prototype (ZP) 2001. Measurements were conducted at room temperature in a White-type cell with effective optical path lengths between 3.2 and 9.6 m and with resolutions ranging from 0.0008 to 0.0018 cm⁻¹ in the region between 600 and 1000 cm⁻¹. The spectrum was analyzed in the ν₄ (), ν_10b () and ν_6b regions of pyrimidine () using an effective Hamiltonian. A total of about 15 000 rovibrational transitions were assigned. The root mean square deviations of the fitted data are in the ranges d_rms = 0.00018-0.00024 cm⁻¹, indicating an excellent agreement of experimental line data with the calculations. The results are discussed briefly in relation to possible extensions to spectra of DNA bases and to intramolecular vibrational redistribution at higher energy. The analysis of the ν_10b and ν₄ bands will also be useful in the interstellar search for pyrimidine in the infrared region.     

15.

Direct observation of the D′ 2_g(P₂)-A′ Π(2_u) system for Cl₂ by laser induced fluorescence spectroscopy: Determination of the absolute position of the A′ state     

Takashi Yoshikawa 《Journal of Molecular Spectroscopy》2007,241(2):230-236

In a discharged supersonic jet of Cl₂, transitions of the D′ 2_g(³P₂)-A′ ³Π(2_u) system for ³⁵Cl₂ were observed directly by laser induced fluorescence spectroscopy. By a discharge in Cl₂, the Cl₂ molecules were populated into the A′ state, which is a metastable and optically forbidden state, from the state. An ultraviolet laser radiation excites the molecules to the D′ ion-pair state. A set of Dunham parameters for the A′ state is determined from a global least-squares fitting for 59 vibronic bands with v″ = 0-7. In the fitting, the previously reported data, T(v) and B(v) for the v = 14 and 15 bands of the A′ state [T. Ishiwata, A. Ishiguro, K. Obi, J. Mol. Spectrosc. 147 (1991) 300-320], were included. Y₀₀ = 57295.723(5) cm⁻¹ of the D′ state [J.-H. Si, T. Ishiwata, K. Obi, J. Mol. Spectrosc. 147 (1991) 334-345] was also included in the global fitting in order to determine the absolute position of the A′ state. The determined parameters of the A′ state are Y₀₀ = 17171.506(14), Y₁₀ = 255.915(85), Y₂₀ = −4.465(70), Y₃₀ = −8.7(23) × 10⁻², Y₄₀ = 6.3(35) × 10⁻³, Y₅₀ = −4.9(26) × 10⁻⁴, Y₆₀ = 1.43(69) × 10⁻⁵, Y₀₁ = 0.16282(15), Y₁₁ = −2.363(68) × 10⁻³, Y₂₁ = −5.01(93) × 10⁻⁵, and Y₃₁ = −3.01(36) × 10⁻⁶ (in cm⁻¹ and one standard deviations of the fit in parentheses). The absolute position of the A′ state is determined with good accuracy.     

16.

Perpendicular magnetic anisotropy and magnetic proximity effect in Pt_1−δFe_δ/Co multilayer films     

Q.L. LvJ.W. Cai  S.L. HeL. Sun 《Journal of magnetism and magnetic materials》2011,323(5):465-470

The perpendicular magnetic anisotropy (PMA) and magnetization in Pt_1−δFe_δ/Co (δ=0, 0.017, 0.04 and 0.06) multilayer films have been investigated. It is found that, on adding a small amount of Fe into the Pt layers, Pt/Co multilayer films maintain well-defined PMA at both 5 and 300 K along with significantly enhanced magnetization even at room temperature, which is far greater than the Curie temperature of Pt_1−δFe_δ dilute alloys. Further study demonstrates that the large enhancement of the magnetization in the Fe doped Pt/Co multilayers at 300 K arises from the bulk moment of the Pt_1−δFe_δ layers at the interface region, where the ferromagnetic order persists up to room temperature due to the strengthened exchange interactions between Fe atoms via strongly polarized Pt near the Pt_1−δFe_δ/Co interfaces. For the Pt_0.96Fe_0.04/Pt multilayers, the magnetically ordered region in each Pt_0.96Fe_0.04 layer extends over at least 10 Å from the interface at room temperature.     

17.

Effective correlation-free reduced Hamiltonian for the ν_t(E), ν_n(A₁) Coriolis-interacting states of C_3v symmetric-top molecules     

Lucie Nová St?íteská  Kamil Sarka 《Journal of Molecular Spectroscopy》2009,256(1):135-140

The effective correlation-free vibrational-rotational Hamiltonian for the Coriolis-interacting ν_t(E) and ν_n(A₁) states in C_3v molecules has been derived. The Hamiltonian includes the terms describing the x-y Coriolis interaction up to the fourth-order, and several useful reduction schemes for the Hamiltonian are suggested.     

18.

Synthesis and magnetic properties of Co_1−xZn_xFe₂O_4+γ nanoparticles as materials for magnetic fluid hyperthermia     

M. Veverka  P. Veverka  O. Kaman  K. Kní?ek  E. Pollert 《Journal of magnetism and magnetic materials》2010,322(16):2386-2389

Nanoparticles of the single spinel phase Co_1−xZn_xFe₂O_4+γ of mean size 3-23 nm, as determined by X-ray diffraction analysis, were synthesized by the co-precipitation method followed by a temperature treatment. Magnetic studies carried out in the range of 4.5-550 K revealed gradual transition from ferrimagnetic to superparamagnetic to paramagnetic behaviour depending on the composition and particle size. The observed behaviour indicates a broad distribution of volume sizes of the nanoparticles. Particular importance can be ascribed to the composition of x=0.6 where the observed transition temperature to the paramagnetic state at 310-334 K suggests applicability of this material for magnetic fluid hyperthermia in a self-controlled regime.     

19.

Formation of α-Si_1−xC_x:H and nc-SiC films grown by HWCVD under different process pressure     

Tianru WuHonglie Shen  Bin ChengYuanyuan Pan  Bing LiuJiancang Shen 《Applied Surface Science》2011,258(3):999-1003

In this work, hydrogenated amorphous silicon carbide (α-Si_1−xC_x:H) and nanocrystalline SiC (nc-SiC) thin films were deposited by hot wire CVD (HWCVD) using SiH₄/C₂H₂/H₂ gas mixtures. It was found that the films prepared under low gas pressure were α-Si_1−xC_x:H and those prepared under high gas pressure were nc-3C-SiC. The α-Si_1−xC_x:H films showed enhanced density of C-H_n and Si-C bonds with increasing C₂H₂ fraction, which induced an increase in optical gap from 1.8 to 3.0 eV. For the deposition process of nc-SiC, the E_g opt of the deposited films varied from 1.9 eV to 2.5 eV as the filament temperature increased from 1700 to 2100 °C. The deposition rate decreased rapidly from 5.74 nm/min to 0.8 nm/min with increasing T_F.     

20.

Experimental study of the Na₂ 3Π_g state     

Chin-Chun Tsai  Ray-Yuan Chang  Thou-Jen Whang 《Journal of Molecular Spectroscopy》2005,232(1):66-72

The 3¹Π_g state of Na₂ is experimentally investigated by using high resolution cw optical-optical double resonance spectroscopy. A single line Ar⁺ laser (total of 9 lines) is used to pump the sodium dimers from thermally populated ground state to the intermediate B¹Π_u state. Then a single mode Ti:sapphire laser is used to probe the 3¹Π_g state. Violet fluorescence from highly Rydberg excited states (mainly 2³Π_g or 3³Π_g states which are transferred from 3¹Π_g state via collisions) to the state is monitored by a filtered photomultiplier tube and a lock-in amplifier. Compared with previous studies [C.C. Tsai, J.T. Bahns, W.C. Stwalley, J. Chem. Phys. 99 (1993) 7417], a wider range of rotational quantum numbers of data field are observed. A set of Dunham coefficients and the Rydberg-Klein-Rees potential energy curve of the 3¹Π_g state are deduced from all the observed rovibrational levels.     

	$\text{T}{}_{\mathrm{e}}\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$	$\text{ω}{}_{\mathrm{e}}\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$	$\text{B}{}_{\mathrm{e}}\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$	$\text{R}{}_{\mathrm{e}}\text{(}\text{A}\text{?}\text{)}$
$\text{E}{}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$	20195.23	29.10	0.00891	5.340733
(1) ${}^1\text{Π}{}_{\mathrm{g}}$	13913.42	18.44	0.00781	5.697722

The CΠu state of Na2 revisited: A comprehensive study by polarization labeling spectroscopy technique

This paper contains the analysis of the C(2)¹Π_u state of Na₂ molecule based on a large data set (3030 lines) obtained from a polarization labeling spectroscopy experiment on the transition. The energies of rovibrational levels in the C state, spanning a wide range of v (0 ? v ? 43) and J (12 ? J ? 100) quantum numbers, are fitted to a Dunham polynomial expansion and also to a numerical potential curve constructed by the inverted perturbation approach (IPA) method.     

Co-L3 X-ray absorption near-edge structure analysis of Pr1−xCaxCoO3−δ and Pr1−xSrxCoO3−δ

The valence state of Co ions in Pr_1−xCa_xCoO_3−δ and Pr_1−xSr_xCoO_3−δ has been investigated by an analysis of the Co-L₃ X-ray absorption near-edge structure (XANES) profile. The observed intensity distributions of Co-L₃ XANES change continuously with increasing concentration of alkaline-earth ions. To investigate the origin of this change in the XANES profile, charge transfer multiplet calculations were carried out, which could successfully explain the change in the spectral profile; they also suggest that the valence state of Co ions in Pr_1−xCa_xCoO_3−δ and Pr_1−xSr_xCoO_3−δ is between 3+ and 4+ and increases gradually with the concentration of alkaline-earth ions.     

Exact PsTd invariant and PsTd symmetric breaking solutions,symmetry reductions and Bäcklund transformations for an AB–KdV system

In natural and social science, many events happened at different space–times may be closely correlated. Two events, A (Alice) and B (Bob) are defined as correlated if one event is determined by another, say, $B=\stackrel{?}{f}A$ for suitable $\stackrel{?}{f}$ operators. A nonlocal AB–KdV system with shifted-parity ($P_s$, parity with a shift), delayed time reversal ($T_d$, time reversal with a delay) symmetry where $B=\stackrel{?}{P_s}\stackrel{?}{T_d}A$ is constructed directly from the normal KdV equation to describe two-area physical event. The exact solutions of the AB–KdV system, including $P_s{T}_d$ invariant and $P_s{T}_d$ symmetric breaking solutions are shown by different methods. The $P_s{T}_d$ invariant solution show that the event happened at A will happen also at B. These solutions, such as single soliton solutions, infinitely many singular soliton solutions, soliton–cnoidal wave interaction solutions, and symmetry reduction solutions etc., show the AB–KdV system possesses rich structures. Also, a special Bäcklund transformation related to residual symmetry is presented via the localization of the residual symmetry to find interaction solutions between the solitons and other types of the AB–KdV system.     

Structure and magnetism in Ho1−xSrxCoO3−δ

We have magnetically and structurally characterized the Ho_1−xSr_xCoO_3−δ family of materials where 0.67≤x≤0.95. The solid solution range and evolution of the structure as a function of x is established and correlated with the broad range of magnetic behavior observed. The structure is shown to be tetragonal I4/mmm although is possibly cubic when x=0.95. For 0.67≤x≤0.9 the material shows antiferromagnetic long range order and ferromagnetic clusters. At x=0.95 the magnetic transition is at 120 K and the imaginary susceptibility becomes non-zero and the temperature of the cusp in the ac susceptibility shows a frequency dependence indicative of glassiness.     

Structural and superconductivity study on α-FeSex

We have successfully synthesized the α-FeSe_x binary tetragonal superconductors with nominal composition of FeSe_x (x=0.6-1.0) via conventional solid state reactions between Fe and Se sealed in quartz tubes. Fe and β-FeSe are the most commonly seen impurities in this binary system. A low-temperature annealing at 400 °C is found to be crucial to remove β-FeSe, which is the thermodynamic stable phase with hexagonal symmetry. For all the samples of FeSe_x, superconductivity is confirmed by magnetic measurements as well as resistivity measurements with their T_c at around 8 K. We noticed that their T_c does not vary with the different nominal Se amount. High-resolution synchrotron X-ray diffraction analysis revealed that the unit cell parameters of all these samples do not change within the error range, and their structure only tolerate the same very small amount of Se deficiency. Based on this study, we concluded that the α-FeSe_x superconductor only exist in a very narrow deficiency range.     

TE1n /TM1n激励圆锥喇叭辐射功率测量方法

研究了TE1n /TM1n模式激励的圆形口径喇叭天线的辐射场特征,导出了根据辐射场计算天线辐射总功率的方法:通过测定天线E面和H面的辐射场功率密度分布,分别进行球冠积分,其平均值即为天线的辐射总功率;并进行了数值仿真验证。分析了测量角度范围和测量点数目对测量功率的影响,提出了通过数据拟合来降低测量误差的一种方法;给出了测量角度范围和测量点数的选取原则,功率测量可在15 dB或18 dB波束宽度范围内进行,测量点数一般选15个左右。     

Ar+ laser-induced fluorescence spectra of Cs2: The E1Σu+ and (1) 1Πg electronic states

Laser-induced fluorescence of Cs₂ molecules in the infrared (1.15–2.5 μm) and the visible (505–545 nm) regions has been observed using several excitation wavelengths from an argonion laser. Accurate molecular constants and potential energy curves for the pumped E¹Σ_u⁺ state and the first excited gerade ¹Π state are derived from more than 1300 fluorescence lines precisely measured with a high-resolution Fourier transform interferometer. The main molecular constants for the states are

Electrical conductivity and structural stability of SrCo1−xFexO3−δ

Perovskite compounds in the system of SrCo_1−xFe_xO_3−δ (x=0.2, 0.4 and 0.6) were synthesized by solid state reaction. SrCo_1−xFe_xO_3−δ shows the p-type small polaron conduction behavior. Electrical conductivity and oxygen vacancy content decrease with increase in Fe content. The incorporation of Fe increases the structural stability of SrCo_1−xFe_xO_3−δ at low temperatures, while decreasing the structural stability at high temperatures. Oxygen partial pressure has a strong influence on electrical conductivity. At low oxygen partial pressure, SrCo_0.8Fe_0.2O_3−δ will transform from cubic to orthorhombic structure. This structure can remain in 5%H₂/Ar only for a short time and then dissociates into Sr₃Fe₂O_6.64 and Co due to the reduction of B-site elements.     

Mixed electrical conduction in Ce1−xCaxO2−x

The solid electrolyte Ce_1?xCa_xO_2-?x with the fluorite-type structure (Ca-doped CeO₂) is a mixed conductor. Conduction occurs predominantly by migration of O^2? ions via oxygen vacancies or by electrons, depending on the departure from stoichiometry. The ionic transference number σ_i/σ_i + σ_e was determined as a function of dopant concentration (0.07?x?0.15), temperature (400–800°C), and oxygen pressure by emf measurements with oxygen concentration cells. It is described by

The entropy term S¹(x) changes from 38.7k for x = 0.07 to 31.7k for x = 0.15; the enthalpy term, 5.42 eV, is independent of x and in excellent accord with semi-empirical calculations.     

Structural and electronic properties of zinc blende BxAl1−xNyP1−y quaternary alloys via ?rst-principle calculations

The structural and electronic properties of cubic zinc blende BN, BP, AlN and AlP compounds and their B_xAl_1−xN_yP_1−y quaternary alloys, have been calculated using the non relativistic full-potential linearized-augmented plane wave FP-LAPW method. The exchange-correlation potential is treated with the local density approximation of Perdew and Wang (LDA-PW) as well as the generalized gradient approximation (GGA) of Perdew-Burke and Ernzerhof (GGA-PBE). The calculated structural properties of BN, BP, AlN and AlP compounds are in good agreement with the available experimental and theoretical data. A nonlinear variation of compositions x and y with the lattice constants, bulk modulus, direct and indirect band gaps is found. The calculated bowing of the fundamental band gaps is in good agreement with the available experimental and theoretical value. To our knowledge this is the first quantitative theoretical investigation on B_xAl_1−xN_yP_1−y quaternary alloy and still awaits experimental confirmations.     

High temperature transport and thermoelectric properties of Ca3−xErxCo4O9+δ

Ca_3−xEr_xCo₄O_9+δ (x=0, 0.05, 0.15, 0.3 and 0.5) samples were prepared using a sol-gel method followed by hot-pressing sintering technique. Powder X-ray diffraction analysis showed the single-phases of Ca_3−xEr_xCo₄O_9+δ were obtained up to x=0.3 and the crystallinity of the samples decreased with increasing Er-doping amount. The high-temperature (323-1073 K) thermoelectric properties of the samples were investigated. The substitution of Er³⁺ for Ca²⁺ resulted in the decrease of electrical conductivity, thermal conductivity and the increase of Seebeck coefficient for all the samples except the x=0.05 one. The dimensionless figure of merit ZT reached 0.28 at 1073 K for Ca_2.7Er_0.3Co₄O_9+δ, indicating the thermoelectric properties of CaCo₄O_9+δ can be enhanced by doping Er in the system.     

Nanocomposite L10 FePt–SiNx and FePt–SiNx–C films with large coercivity and small grain size on a TiN intermediate layer

FePt–SiN_x–C films with high coercivity, (001) texture and small grain size were obtained by co-sputtering FePt, Si₃N₄ and C on TiN/CrRu/glass substrate at 380 °C. Without C doping, FePt–SiN_x films with good perpendicular anisotropy and a single layer structure were obtained. However, the grain size was still too large and the grain isolation was poor. When C was doped into the FePt–SiN_x films, the out-of-plane coercivity increased due to the decrease of the exchange coupling. In addition, the grain size of the FePt films decreased, and well-separated FePt grains with uniform size were formed. The microstructure of [FePt–SiN_x 40 vol%]−20 vol% C films changed from a single layer structure to a multiple layer structure when the FePt thickness was increased from 4 to 10 nm. By optimizing the sputtering process, the [FePt (4 nm)–SiN_x 40 vol%]−20 vol% C (001) film with coercivity higher than 21.5 kOe, a single layer structure, and small average FePt grain size of 5.6 nm was obtained, which makes it suitable for ultrahigh density perpendicular recording.     

High resolution rovibrational spectroscopy of pyrimidine: Analysis of the B1 modes ν10b and ν4 and B2 mode ν6b

We report the first high resolution rovibrational analysis of the infrared spectrum of pyrimidine (C₄H₄N₂) based on measurements using our Fourier transform spectrometer, the Bruker IFS 125 HR Zürich Prototype (ZP) 2001. Measurements were conducted at room temperature in a White-type cell with effective optical path lengths between 3.2 and 9.6 m and with resolutions ranging from 0.0008 to 0.0018 cm⁻¹ in the region between 600 and 1000 cm⁻¹. The spectrum was analyzed in the ν₄ (), ν_10b () and ν_6b regions of pyrimidine () using an effective Hamiltonian. A total of about 15 000 rovibrational transitions were assigned. The root mean square deviations of the fitted data are in the ranges d_rms = 0.00018-0.00024 cm⁻¹, indicating an excellent agreement of experimental line data with the calculations. The results are discussed briefly in relation to possible extensions to spectra of DNA bases and to intramolecular vibrational redistribution at higher energy. The analysis of the ν_10b and ν₄ bands will also be useful in the interstellar search for pyrimidine in the infrared region.     

Direct observation of the D′ 2g(P2)-A′ Π(2u) system for Cl2 by laser induced fluorescence spectroscopy: Determination of the absolute position of the A′ state

In a discharged supersonic jet of Cl₂, transitions of the D′ 2_g(³P₂)-A′ ³Π(2_u) system for ³⁵Cl₂ were observed directly by laser induced fluorescence spectroscopy. By a discharge in Cl₂, the Cl₂ molecules were populated into the A′ state, which is a metastable and optically forbidden state, from the state. An ultraviolet laser radiation excites the molecules to the D′ ion-pair state. A set of Dunham parameters for the A′ state is determined from a global least-squares fitting for 59 vibronic bands with v″ = 0-7. In the fitting, the previously reported data, T(v) and B(v) for the v = 14 and 15 bands of the A′ state [T. Ishiwata, A. Ishiguro, K. Obi, J. Mol. Spectrosc. 147 (1991) 300-320], were included. Y₀₀ = 57295.723(5) cm⁻¹ of the D′ state [J.-H. Si, T. Ishiwata, K. Obi, J. Mol. Spectrosc. 147 (1991) 334-345] was also included in the global fitting in order to determine the absolute position of the A′ state. The determined parameters of the A′ state are Y₀₀ = 17171.506(14), Y₁₀ = 255.915(85), Y₂₀ = −4.465(70), Y₃₀ = −8.7(23) × 10⁻², Y₄₀ = 6.3(35) × 10⁻³, Y₅₀ = −4.9(26) × 10⁻⁴, Y₆₀ = 1.43(69) × 10⁻⁵, Y₀₁ = 0.16282(15), Y₁₁ = −2.363(68) × 10⁻³, Y₂₁ = −5.01(93) × 10⁻⁵, and Y₃₁ = −3.01(36) × 10⁻⁶ (in cm⁻¹ and one standard deviations of the fit in parentheses). The absolute position of the A′ state is determined with good accuracy.     

Perpendicular magnetic anisotropy and magnetic proximity effect in Pt1−δFeδ/Co multilayer films

The perpendicular magnetic anisotropy (PMA) and magnetization in Pt_1−δFe_δ/Co (δ=0, 0.017, 0.04 and 0.06) multilayer films have been investigated. It is found that, on adding a small amount of Fe into the Pt layers, Pt/Co multilayer films maintain well-defined PMA at both 5 and 300 K along with significantly enhanced magnetization even at room temperature, which is far greater than the Curie temperature of Pt_1−δFe_δ dilute alloys. Further study demonstrates that the large enhancement of the magnetization in the Fe doped Pt/Co multilayers at 300 K arises from the bulk moment of the Pt_1−δFe_δ layers at the interface region, where the ferromagnetic order persists up to room temperature due to the strengthened exchange interactions between Fe atoms via strongly polarized Pt near the Pt_1−δFe_δ/Co interfaces. For the Pt_0.96Fe_0.04/Pt multilayers, the magnetically ordered region in each Pt_0.96Fe_0.04 layer extends over at least 10 Å from the interface at room temperature.     

Effective correlation-free reduced Hamiltonian for the νt(E), νn(A1) Coriolis-interacting states of C3v symmetric-top molecules

The effective correlation-free vibrational-rotational Hamiltonian for the Coriolis-interacting ν_t(E) and ν_n(A₁) states in C_3v molecules has been derived. The Hamiltonian includes the terms describing the x-y Coriolis interaction up to the fourth-order, and several useful reduction schemes for the Hamiltonian are suggested.     

Synthesis and magnetic properties of Co1−xZnxFe2O4+γ nanoparticles as materials for magnetic fluid hyperthermia

Nanoparticles of the single spinel phase Co_1−xZn_xFe₂O_4+γ of mean size 3-23 nm, as determined by X-ray diffraction analysis, were synthesized by the co-precipitation method followed by a temperature treatment. Magnetic studies carried out in the range of 4.5-550 K revealed gradual transition from ferrimagnetic to superparamagnetic to paramagnetic behaviour depending on the composition and particle size. The observed behaviour indicates a broad distribution of volume sizes of the nanoparticles. Particular importance can be ascribed to the composition of x=0.6 where the observed transition temperature to the paramagnetic state at 310-334 K suggests applicability of this material for magnetic fluid hyperthermia in a self-controlled regime.     

Formation of α-Si1−xCx:H and nc-SiC films grown by HWCVD under different process pressure

In this work, hydrogenated amorphous silicon carbide (α-Si_1−xC_x:H) and nanocrystalline SiC (nc-SiC) thin films were deposited by hot wire CVD (HWCVD) using SiH₄/C₂H₂/H₂ gas mixtures. It was found that the films prepared under low gas pressure were α-Si_1−xC_x:H and those prepared under high gas pressure were nc-3C-SiC. The α-Si_1−xC_x:H films showed enhanced density of C-H_n and Si-C bonds with increasing C₂H₂ fraction, which induced an increase in optical gap from 1.8 to 3.0 eV. For the deposition process of nc-SiC, the E_g opt of the deposited films varied from 1.9 eV to 2.5 eV as the filament temperature increased from 1700 to 2100 °C. The deposition rate decreased rapidly from 5.74 nm/min to 0.8 nm/min with increasing T_F.     

Experimental study of the Na2 3Πg state

The 3¹Π_g state of Na₂ is experimentally investigated by using high resolution cw optical-optical double resonance spectroscopy. A single line Ar⁺ laser (total of 9 lines) is used to pump the sodium dimers from thermally populated ground state to the intermediate B¹Π_u state. Then a single mode Ti:sapphire laser is used to probe the 3¹Π_g state. Violet fluorescence from highly Rydberg excited states (mainly 2³Π_g or 3³Π_g states which are transferred from 3¹Π_g state via collisions) to the state is monitored by a filtered photomultiplier tube and a lock-in amplifier. Compared with previous studies [C.C. Tsai, J.T. Bahns, W.C. Stwalley, J. Chem. Phys. 99 (1993) 7417], a wider range of rotational quantum numbers of data field are observed. A set of Dunham coefficients and the Rydberg-Klein-Rees potential energy curve of the 3¹Π_g state are deduced from all the observed rovibrational levels.