Vortex penetration depth of κ-(ET)2Cu[N(CN)2]Br

The magnetic field dependence of the in-plane penetration depth λ_|(H) for single crystal κ-(ET)₂Cu[N(CN)₂]Br has been measured at 3, 9.6, and 36 MHz. Over a limited range, λ_| scales with a characteristic field that coincides with a shoulder in the λ_| vs. H curves. Above that field, λ_| increases sharply toward a second inflection point at that coincides with is close to the irreversibility line measured by magnetization. For fields larger than the penetration depth diverges, suggesting that the vortex lattice has melted. The field dependence at one frequency agrees qualitatively with a model of pinned vortices at low fields giving way to flux flow at higher fields. However, the observed frequency dependence deviates significantly from the predictions of this model, suggesting that collective effects play a major role. Our technique also yields a new measurement for the interplane penetration depth λ_⊥ ∼ 300 μm, implying an anisotropy .     

First-principle study on the electronic structure and the anti-ferromagnetic properties of the organic-inorganic hybrid compound [Co(μ1,3-SCN)2(μ1,6-dmpzdo)]n

The electronic and the magnetic properties of the molecule-based magnet [Co(μ_1,3-SCN)₂(μ_1,6-dmpzdo)]n (where dmpzdo=2,5-dimethylpyrazine-1,4-dioxide) have been investigated using first-principles, namely density-functional theory (DFT) with the generalized gradient approximation (GGA) method and the full-potential linearized augmented plane-wave method (FP_LAPW). The total energy, the spin magnetic moments and the density of states (DOSs) were all calculated and spin distributions in ferromagnetic and anti-ferromagnetic (AFM) states of it have been obtained by the calculation. The electronic structure and magnetic coupling between cobalt ions along chain are discussed, and the calculations reveal that the compound [Co(μ_1,3-SCN)₂(μ_1,6-dmpzdo)]n has a stable anti-ferromagnetic ground state, which is in good agreement with the experimental results.     

Crystal field study and magnetic properties of [TbCu6(μ3OH)3(HL)2(L)4](ClO4)2·25H2O (H2L=imino-diacetic acid)

A crystal field (CF) investigation of the magnetic properties of [TbCu₆(μ₃-OH)₃(HL)₂(L)₄](ClO₄)₂·25H₂O (H₂L=imino-diacetic acid) has been carried out. An enhancement of the average magnetic susceptibility (defined by =(χ_||+2χ_⊥)/3, where χ_|| and χ_⊥ are the magnetic susceptibilities parallel and perpendicular to the symmetrical axis of the cluster) with respect to the Tb³⁺ free ion value has been noticed and is attributed to the Tb-Cu interaction. The CF parameters obtained for the system for the first time have been exploited to find the Stark splitting of the ⁷F manifold of Tb³⁺, paramagnetic resonance g-values, and the heat capacity. Two anomalies are obtained in the heat capacity at 40 and 5 K; the peak values are 3.1 and 5.98 J mol⁻¹ K⁻¹, respectively.     

分子基磁体Cr[N(CN)2]2电子结构和半金属性的第一性原理研究

基于第一性原理方法结合广义梯度近似,研究了分子基磁体Cr[N(CN)₂]₂的电子结构和半金属性. 对总能量,自旋极化的能带结构,态密度以及自旋磁矩的计算表明该分子磁体为半金属铁磁体．每个分子的总磁矩为2.00μB,其中Cr²⁺对分子磁矩的贡献较大,而配位体上的碳原子和氮原子的贡献相对较小．讨论了当晶格常数发生小幅变化时材料半金属性的变化.     

Transport studies at the Mott transition of the two-dimensional organic metal κ-(BEDT-TTF)2Cu[N(CN)2]BrxCl1-x

The two-dimensional organic conductor κ-(BEDT-TTF)₂Cu[N(CN)₂]Br _x Cl_{1- x} undergoes a transition from an insulator to a superconductor upon substituting Cl by Br. We have performed in- and out-of-plane electric-transport measurements on the alloyed series with x = 20%, 40%, 70%, 80%, 85%, and 90% as a function of temperature in order to explore the bandwidth-controlled phase transition between the Mott insulator and the Fermi-liquid. All crystals exhibit a similar semiconducting behavior of ρ(T) from room temperature down to 100 K. Below approximately 50 K, a metal-to-insulator transition is found for compounds with x < 70%. Out of this Mott insulating state, magnetic order develops below T _N ≈ 25 K. The Br-rich samples cross a bad-metal regime before they become coherent metals and eventually superconducting at T _c ≈ 12 K. For these systems the resistivity at T _c ≤ T ≤ T ₀ reveals a ρ(T) ∝ T ² dependence associated with a strongly correlated Fermi-liquid, limited by some characteristic temperature T ₀. The conclusions are corroborated by data from microwave, magnetic and optical experiments.     

Observation of simultaneous ν1(SF6) + ν3(NF3) and ν2(SF6) + ν3(NF3) transitions enhanced by the resonance dipole-dipole interaction with the ν1 + ν3 and ν2 + ν3 states of the SF6 molecule

IR spectra of the solution of SF₆ molecules in liquid NF₃ at 84 K have been recorded. In a solvent transmission window of 1500–1750 cm⁻¹, two wide absorption bands with pronounced peaks in the high-frequency part are observed. The profile of these bands is explained by the influence of the resonance dipole-dipole (RDD) interaction of the states of the simultaneous transition ν₁(SF₆) + ν₃(NF₃) and ν₂(SF₆) + ν₃(NF₃) with the states (ν₁ + ν₃) and (ν₂ + ν₃) of the SF₆ molecules, respectively. The use of three isotopic modifications ³²SF₆, ³³SF₆, and ³⁴SF₆ has allowed us to vary the resonance detuning and thus to change the strength of the RDD interaction. With the liquid near the melting point being represented as a close-packed cubic crystal, the profile was calculated and its spectral characteristics were determined. The frequencies of the main peaks coincide with the experimental values accurate to the error.     

High-resolution rovibrational study of the Coriolis-coupled ν12 and ν15 modes of [1.1.1]propellane

Infrared spectra of the small strained cage molecule [1.1.1]propellane have been obtained at high resolution (0.0015 cm⁻¹) and the J, K, and l rovibrational structure has been resolved for the first time. We recently used these spectra to obtain combination-differences to deduce ground state parameters for propellane; over 4100 differences from five fundamental and four combination bands were used in the fitting process. The combination-difference approach eliminated potential errors caused by localized perturbations in the upper states and gave well-determined ground state parameters. In the current work, these ground state constants were fixed when fitting the upper state parameters for the ν₁₂ (e′) perpendicular and parallel bands. Over 4000 infrared transitions were fitted for each band, with J, K values ranging up to 71, 51 and 92, 90, respectively. While the transition wavenumbers for both bands can be fit nicely using separate analyses for each band, the strong intensity perturbations observed in the weaker ν₁₂ band indicated that Coriolis coupling between the two modes was significant and should be included. Due to correlations with other parameters, the Coriolis coupling parameter for the ν₁₅ and ν₁₂ interaction is poorly determined by a transition wavenumber fit alone but, fortunately, the intensity perturbations gave useful added constraints on . By combining the wavenumber fit with a fit of experimental intensities, a value of −0.42 was obtained, quite close to the value of −0.44 predicted by Gaussian ab initio density functional calculations using a cc-pVTZ basis. This intensity fit also yielded a (∂μ^z/∂Q₁₅)/(∂μ^x/∂Q_12a) dipole derivative ratio of 36.5, in reasonable agreement with a value of 29.2 predicted by the ab initio calculations. This ratio is unusually high due to large charge movement as the novel central C_axial-C_axial bond is displaced along the symmetry axis of the molecule for the ν₁₅ mode.     

Optical investigations of intermolecular electronic interactions and “free” charge carriers in quasi-two-dimensional organic conductors and superconductors of the group κ-(BEDT-TTF)2Cu[N(CN)2]BrxCl1 ? x

The reflectance spectra and optical conductivity spectra of quasi-two-dimensional organic conductor crystals of the group of compounds κ-(BEDT-TTF)₂Cu[N(CN)₂]Br _x Cl_{1 − x} with x = 0, 0.40, 0.73, 0.85, and 0.90 in the spectral region from 6 meV to 0.74 eV at temperatures T = 90-20 K have been quantitatively analyzed in the framework of a combined semiempirical model including the cluster (tetramer) theory for strongly correlated electrons coupling with intramolecular vibrations and the Drude theory of free electrons with the aim of studying intermolecular electronic interactions and their influence on the formation of the ground state in these crystals. It has been established that the parameters characterizing the charge transfer between molecules in dimers and tetramers and the vibronic coupling constants are almost identical for the compounds under investigation. A large value of the effective Coulomb repulsion (U/t = 1.3–1.5) indicates that strong electron correlations occur in the compounds both with a metal-insulator phase transition (x = 0, 0.40) and with a metal-superconductor phase transition (x = 0.85, 0.90). The conclusion has been drawn that, at x = 0, electron correlations favor an antiferromagnetic spin ordering and a metal-insulator phase transition, whereas for superconductors (x = 0.85, 0.90), the metal-insulator phase transition is hindered as a result of the structural disorder due to the difference in orientations of the terminal CH₂ groups of the BEDT-TTF molecule. It has been shown that quasi-free charge carriers interact with electrons localized on the clusters and do not interact with intramolecular vibrations. It has been noted that the oscillator strength of the observed electronic transitions in the initial metallic band (N _eff = 0.38–0.31 per dimer) is considerably less than the corresponding value for free (noninteracting) charge carriers (N = 1). This suggests that the Coulomb correlations and vibronic coupling play a decisive role in the kinetic phenomena observed in the molecular conductors and superconductors under investigation.     

超高泵浦功率下的Xe(6p[1/2]0, 6p[3/2]2, 和6p[5/2]2)原子的能量转移过程

本文研究了Xe(6p[1/2]₀, 6p[3/2]₂, and 6p[5/2]₂)原子在聚焦条件下的动力学过程. 激发能级的原子密度在聚焦条件下会显著地增加,因此两个高激发态原子之间的energy-pooling碰撞的概率也会增加. 这种energy-pooling碰撞主要有三种类型. 第一种类型为energy-pooling碰撞导致的电离. 一旦将激发激光聚焦,就可以从侧面的窗口观察到非常明显的电离现象,不论激发能级是6p[1/2]₀、6p[3/2]₂或6p[5/2]₂能级. 这种电离的产生机理是energy-pooling电离或者一个Xe^*原子再吸收一个光子产生电离. 第二种类型为跨越较大能极差的energy-pooling碰撞. 当激发能级为6p[1/2]₀能级的情况下,两个6p[1/2]₀原子碰撞会产生一个5d[3/2]₁原子和一个6s''[1/2]₀原子. 第三种类型为跨越较小能级差的energy-pooling碰撞. 以5个二次产生的6p能级为上能级的荧光强度都变得更强,并且这些荧光的上升沿都变得更陡峭. 产生这些6p原子的主要机理是energy-pooling碰撞并非简单的碰撞弛豫. 基于理想气体原子之间的碰撞概率公式,推导出两个6p[1/2]₀原子的energy-pooling碰撞速率为6.39x10⁸s^-1. 此外,6s原子在聚焦条件下的密度也会增加. 因此所有的荧光曲线会因为辐射俘获效应而出现非常严重的拖尾.     

Rovibrational analysis of the ν2 and 2ν2 P-D stretching bands of PH2D

The infrared spectral regions of the P-D stretching fundamental band ν₂ and the first overtone band 2ν₂ of PH₂D were recorded with a resolution of 2.7×10⁻³ and , respectively. In the analysis about 710 and 440 transitions were assigned to the ν₂ and 2ν₂ bands. These provided 358 and 268 upper rovibrational energy terms, respectively. Resonance interactions between the states (010000) and (000200) were taken into account in the Hamiltonian used to fit upper energies of the (010000) state. The rovibrational energies of the (020000) state were fitted with a Hamiltonian for an isolated vibrational state.     

Short pulse Z -scan investigations of optical nonlinearities of a novel organometallic complex: [(C2H5)4N]2[Cu(dmit)2] at 532 and 1064?nm

A novel dmit organometallic complex: [(C₂H₅)₄N]₂[Cu(dmit)₂] (dmit^2-=1,3-dithiole-2-thione-4,5-dithiolate), abbreviated as EtCu, was synthesized. Afterwards its optical nonlinearities in acetone solution at 532 nm and 1064 nm were studied by the Z-scan technique with laser pulses of picosecond duration. The two-photon absorption at 1064 nm and the saturable absorption at 532 nm were observed. The Z-scan curves also revealed that EtCu sample solutions exhibited self-defocusing effects at both wavelengths. The origins were analyzed for the differences between the results. All the outcomes suggest that this material is potential for nonlinear optical device applications. PACS 42.65.An; 42.65.Hw; 42.65.Jx; 81.20.Ka; 78.30.Jw     

High-resolution infrared and theoretical study of the fundamental bands ν2, ν4 and ν9 and the c-Coriolis interacting dyad ν5, ν14 of 1,3,4-thiadiazole

The Fourier transform gas-phase IR spectrum of 1,3,4-thiadiazole, C₂H₂N₂S, has been recorded with a resolution of ca. 0.003 cm⁻¹ in the 800-1500 cm⁻¹ spectral region. Five fundamental bands ν₂(A₁; 1391.9 cm⁻¹), ν₄(A₁; 964.4 cm⁻¹), ν₅(A₁; 894.6 cm⁻¹), ν₉(B₁; 821.5 cm⁻¹), and ν₁₄(B₂; 898.4 cm⁻¹) have been analysed using the Watson model. Ground state rotational and quartic centrifugal distortion constants as well as upper state spectroscopic constants have been obtained from fits. The ν₄ and ν₉ bands are unperturbed while a strong c-Coriolis resonance perturbs the close-lying ν₅ and ν₁₄ bands. This dyad system has been analysed by a model including first and second order c-Coriolis resonance using the theoretically predicted Coriolis coupling constant . The ν₂ band is strongly perturbed by a local resonance, and we obtain a set of spectroscopic parameters using a model including second order a-Coriolis resonance with the inactive ν₁₀ + ν₁₄ band. Ground state rotational and quartic centrifugal distortion constants, anharmonic frequencies, and vibration-rotational α-constants predicted by quantum chemical calculations using a cc-pVTZ basis and B3LYP methodology, have been compared with the present experimental data, where there is generally good agreement.     

Structure and broadening coefficients (He, Ar and N2) of the ν4 band of CF4

Spectra of CF₄ in the ν₄ fundamental band region have been recorded in pure gas and in mixtures with He, Ar and N₂ at resolution up to . Obtained data allowed us to evaluate the integrated band intensity, line intensity distribution and effective broadening coefficients for J-multiplets. The broadening coefficient behavior is similar to that previously registered for linear molecules: they coincide for P and R branches; the J-dependence in the case of argon is more pronounced than that for helium. The broadening coefficients for nitrogen and helium are practically the same but the values for nitrogen are scattered around the general trend.Q-branch broadening is different from that for J-manifolds. The coefficients of branch broadening are noticeably smaller. Nitrogen broadening is very close to result for the case of argon though there is a marked difference between them for J-manifolds. Collisions with argon and nitrogen broaden the Q-branch almost 3 times more effectively than collisions with helium.     

High-resolution study of the ν1/ν5 and 2ν1/ν1+ν5 P-H stretching bands of PH2D

The P-H stretching bands ν₁/ν₅ and 2ν₁/ν₁+ν₅ were recorded using a Bruker 120 HR interferometer with a resolution of 0.0042 and 0.0088 cm⁻¹, respectively, and analyzed. From the fits 33 and 50, respectively, vibrational, rotational, centrifugal distortion, and resonance interaction parameters were obtained. These reproduce 668 and 497 rovibrational energies of the pairs of states ν₁/ν₅ and 2ν₁/ν₁+ν₅ with experimental accuracies, rms=0.00016 and , respectively. “Local mode” behavior of the PH₂ fragment is established and discussed in detail.     

Synthesis of [Ru3(μ3-NPh)(Br)(CO)9] on self-assembled monolayers of di(3-aminopropyl)viologen/ITO surfaces and its application to photoelectrochemical cells

Triruthenium carbonyl clusters {[Ru₃(Br)(CO)₁₁]⁻ (denoted as Ru-1), [Ru₃(μ₂-Br)(CO)₁₀]⁻ (denoted as Ru-2), and [Ru₃(μ₃-NPh)(Br)(CO)₉]⁻ (denoted as Ru-3)} were synthesized on di(3-aminopropyl)viologen (DAPV)/indium tin oxide (ITO) using a surface reaction in a ruthenium (III) carbonyl [Ru₃(CO)₁₂] solution, and were applied to photoelectrochemical cells (PECs) at the molecular level. The formation of DAPV on ITO was realized in the form of self-assembled monolayers. Ru₃(CO)₁₂ then easily reacted with the Br⁻ of DAPV, and a mixture of Ru-1 and Ru-2 was formed on DAPV/ITO. Furthermore, Ru-3 was successfully anchored on DAPV/ITO by adding nitrosobenzene in order to react with Ru-2 on DAPV/ITO. The photocurrents of (Ru-1 and Ru-2)/DAPV/ITO and Ru-3/DAPV/ITO in PECs at the molecular level were 6.3 nA cm⁻² and 8.6 nA cm⁻², respectively. The quantum yield of Ru-3/DAPV/ITO was ∼0.8%. Time-resolved photoluminescence spectroscopy and emission spectroscopy were recorded to bring out the photoinduced charge transfer process from ruthenium clusters to DAPV.     

First-principles study on the electronic structure and the ferromagnetic properties of the cyano-bridged bimetallic compound Mn2(H2O)5Mo(CN)7·4H2O (α phase)

First-principles calculations have been performed to study the electronic structure and the ferromagnetic properties of the cyano-bridged bimetallic compound Mn₂(H₂O)₅Mo(CN)₇·4H₂O (α phase).The calculations were based on density-functional theory and the full potential linearized augmented plane wave method (FP-LAPW). The calculated total energies revealed that the compound has a stable ferromagnetic (FM) ground state, which is in agreement with the experiments. The electronic structure of the compound has a half-metallic behavior. The calculated magnetic moment per molecule is about 15.000 μ_B, the magnetic moment are mainly from Mo and Mn atoms with d electronic configuration. It is also found that there exists ferromagnetic interaction between low-spin Mo²⁺ and high-spin Mn³⁺ ions through the Mo-C-N-Mn linear linkages.     

Mg2(BH4)2(NH2)2脱氢机理的理论研究

对Mg₂(BH₄)₂(NH₂)₂的脱氢机理展开系统的理论研究发现相对于分子内的脱氢过程,分子间的脱氢过程在热力学和动力学方面都是比较有利的. Mg₂(BH₄)₂(NH₂)₂脱氢过程的第一步是BH₄^-中的B-H^δ-和NH2-中     

Simultaneous analysis of the 2ν2, 2ν5, and ν2 + ν5 vibration-rotation bands of CH3Br

Previous studies of the parallel bands 2ν₂ and $\text{2ν}{}_5{}^0$ of CH₃Br by the two first authors have been completed by the analysis of the weaker perpendicular band ν₂ + ν₅, centered near 2745 cm^?1. It is well known that the v₂ = 1 and v₅ = 1 states of methylbromide are linked by an x-y-type Coriolis interaction. Therefore, in the 2500–2900-cm^?1 range, the levels

$\text{(v}{}_2\text{=2), (v}{}_5\text{2, l}{}_5\text{=0), (v}{}_5\text{=2, l}{}_5\text{±2), (v}{}_5\text{=v}{}_2\text{=1, l=5±1)}$

are linked by a similar interaction. Least-squares and prediction programs have been written to treat this kind of problems and they have been satisfactorily applied to both isotopic species, CH₃⁷⁹Br and CH₃⁸¹Br. A localized resonance in the K = 0 subband of ν₂ + ν₅ has been shown to be due to the 3ν₃ + ν₆ band. No evidence for a strong Fermi resonance between ν₁ and $\text{2ν}{}_5{}^0$ has been found.     

Line shifts in the ν2, 2ν2, and ν4 bands of NH3 perturbed by O2

Pressure-induced line shift coefficients have been measured for more than 200 rovibrational lines of NH₃ perturbed by O₂ at room temperature (T = 295 K) in some branches of the ν₂, 2ν₂, and ν₄ bands. These lines with J values ranging from 1 to 13 are located in the spectral range 800-1800 cm⁻¹. Experiments were made with a high-resolution Fourier transform spectrometer. The treatment of vibration-rotation lines includes interference effects caused by the overlapping of lines. The O₂ pressure-induced shift coefficients have been derived from the non-linear least-squares multi-pressure fitting technique. The results illustrate a vibrational dependence of line shifts with vibrational quantum number. Most of the measured shifts are negative in the ν₄ band. They are positive for the ν₂ and 2ν₂ bands. The measured shift coefficients are compared with previous measurements and with those calculated from a semiclassical theory based upon the Robert-Bonamy formalism extended to the case of symmetric top molecule with inversion motion. The predictions are generally in satisfactory agreement with the experimental data. Analyses of measured and predicted results illustrate that these shifts mainly originate from the isotropic part of the intermolecular potential.