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1.
A high-resolution (0.002 cm−1) infrared absorption spectrum of methylene fluoride-d2 (CD2F2) of the lowest fundamental mode ν4 in the region from 460 to 610 cm−1 has been measured on a Bruker IFS 120-HR Fourier transform infrared spectrometer. More than 3500 transitions have been assigned in this B-type band centered at 521.9 cm−1. The data have been combined with upper state pure rotational measurements in a weighted least-squares fit to obtain molecular constants for the upper state resulting in an overall standard deviation of 0.00018 cm−1. Accurate value for the band origin (521.9578036 cm−1) has been obtained and inclusion of transitions with very high J (?60) and Ka (?34) values has resulted in improved precision for sextic centrifugal distortion constants, in particular DK, HKJ, and HK.  相似文献   

2.
Experiments directly probing the electronic states using angle-resolved photoemission (ARPES) were carried out on La2/3Sr1/3MnO3 in order to elucidate its electronic properties. ARPES is a surface sensitive technique where bulk and surface states are usually both present. We present high-resolution ARPES studies in the (1 0 0) and (1 1 0) mirror planes and compare them with simulated ARPES based on GGA + U band structure calculations. In the (1 1 0) mirror plane we identify surface umklapps accounted by surface reconstruction which couple to bulk electronic states. As predicted by the simulated spectra there is additional spectral intensity at the Fermi level detected in ARPES data due to k-broadening effects in the photoemission final states. We demonstrate that this additional spectral intensity is a convenient spectral marker for determination of the kF Fermi momenta.  相似文献   

3.
Lead bismuth arsenate glasses mixed with different concentrations of WO3 (ranging from 0 to 6.0 mol%) were synthesized. Differential thermal analysis (DTA), optical absorption, ESR and IR spectral studies have been carried out. The results of DTA have indicated that there is a gradual decrease in the resistance of the glass against devitrification with increase in the concentration of WO3 upto 4.0 mol%.The optical absorption spectra of these glasses exhibited a relatively broad band peaking at about 880 nm identified due to dxydx2y2 transition of W5+ ions; this band is observed to be more intense in the spectrum of glass containing 4.0 mol% of WO3. Further, two prominent kinks attributed to 3P01S0, 1D2 transitions of Bi3+ ions have also been located in the absorption spectra. The ESR spectra of these glasses recorded at room temperature exhibited an asymmetric signal at g∼1.71 and gll∼1.61. The intensity of the signal is observed to be maximal for the spectrum of the glass W4. The quantitative analysis of optical absorption and ESR spectral studies have indicated that there is a maximum reduction of tungsten ions from W6+ state to W5+ state in the glass containing 4.0 mol% of WO3. The IR spectral studies have indicated that there is a increasing degree of disorder in the glass network with increase in the concentration of WO3 upto 4.0 mol%.  相似文献   

4.
More than 250 rotationally resolved vibrational bands of the A2B2-X2A1 electronic transition of 15NO2 have been observed in the 14 300-18 000 cm−1 range. The bands have been recorded in a recently constructed setup designed for high resolution spectroscopy of jet cooled molecules by combining time gated fluorescence spectroscopy and molecular beam techniques. The majority of the observed bands has been rotationally assigned and can be identified as transitions starting from the vibrational ground state or from vibrationally excited (hot band) states. An exceptionally strong band is located at 14 851 cm−1 and studied in more detail as a typical benchmark transition to monitor 15NO2 in atmospheric remote sensing experiments. Standard rotational fit routines provide band origins, rotational and spin rotation constants. A subset of 177 vibronic levels of 2B2 vibronic symmetry has been analyzed in the energy range between 14 300 and 17 250 cm−1, in terms of integrated density and using Next Neighbor Distribution. It is found that the overall statistical properties and polyad structure of 15NO2 are comparable to those of 14NO2 but that the internal structures of the polyads are completely different. This is a direct consequence of the X2A1-A2B2 vibronic mixing.  相似文献   

5.
Based on extensive Mossbauer effect (ME) and magnetization measurements, the orthorhombic AlFe2B2 was characterized as a ferromagnet (FM) because this character is evident as an onset of a FM transition at Tc=320 K and characteristic magnetizations isotherms below Tc. At liquid helium temperatures, the magnetization saturates to μsat≈1μB per Fe atom; a value which is half the one reported for the iron metal indicating a relatively more filled 3d band. The ME analysis revealed a hyperfine field H(0) of 88(2) kOe, an isomer shift (relative to Fe) of 0.50(2) mm/s, and a quadrupole parameter of 0.02 mm/s: all parameters extrapolated to zero Kelvin. The itinerant character of the magnetic moment will be discussed.  相似文献   

6.
High-resolution Fourier transform spectrum of phosphine (PH3) at room temperature has been recorded in the region of the 3ν2 band (2730-3100 cm−1) at an apodized resolution of 0.005 cm−1. About 200 vibration-rotation transitions have been least squares fitted with an rms of 0.00039 cm−1 after taking into account the ΔK = ±3 interaction.  相似文献   

7.
The rotational spectra of the ground vibrational state and the ν9 = 1 torsional state have been reinvestigated and accurate spectroscopic constants have been determined. The torsional frequency, ν9 = 70(15) cm−1, has been determined by relative intensity measurements. The assignment of the infrared spectrum has been slightly revised and an accurate harmonic force field has been calculated. The equilibrium structure has been determined using different, complementary methods: experimental, semi-experimental and ab initio, leading to r(NN) = 1.870(2) Å, in particular.  相似文献   

8.
Nanocrystalline powders with various Eu3+ concentration (from 1 to 10 mol %) doped La2O3 were prepared via a combustion route. Their structure and morphology were characterized using X-ray diffraction (XRD) and High-resolution transmission electron microscopy. The emission spectra of the as-synthesized samples show that the strongest emission position is centered at 626 nm corresponding to 5D07F2 transition of Eu3+ ions and the intensity change of 626 nm emission is considered as a function of ultraviolet (240 nm) irradiation time. The excitation spectra at 626 nm monitoring indicate that the charge transfer state band is varies with different Eu3+ ion concentration. These results are attributed to the surface defects of the nanocrystals.  相似文献   

9.
This paper reports for the first time both, an experimental observation and theoretical calculations of the K2 43Δg state. For the experiment we used cw perturbation-facilitated optical-optical double resonance (PFOODR) spectroscopy. A single mode Ti-sapphire laser and a dye laser served as the pump and probe lasers, respectively. A total of 55 PFOODR signals have been assigned to the 43Δg ← b3Πu transitions. Absolute vibrational numbering was determined by using quantum defect analysis combined with comparing observed intensities with calculated Franck-Condon factors (FCF). For the former we used known parameters from the 23Δg state since the 23Δg and the 43Δg states belong to the same Rydberg series. We report here our experimental and calculated spectroscopic constants, the corresponding RKR potential energy curve, the Franck-Condon table for the 43Δg ↔ b3 Πu system, as well as a comparison with the theoretical potential energy curve. The Te value is found to be 28408.938(52) cm−1.  相似文献   

10.
We report the iron isotope effect on a transition temperature (Tc) in an optimally-doped (Ba,K)Fe2As2 (Tc = 38 K) and SmFeAsO1−y (Tc = 54 K) superconductors. In order to obtain the reliable isotope shift in Tc, twin samples with different iron isotope mass are synthesized in the same conditions (simultaneously) under high-pressure. We have found that (Ba,K)Fe2As2 shows an inverse iron isotope effect αFe = −0.18 ± 0.03 while SmFeAsO1−y shows a small iron isotope effect αFe = −0.02 ± 0.01, where the isotope exponent α is defined by Tc  Mα (M is the isotopic mass). The results show that αFe changes in the iron-based superconductors depending on the system. The distinct iron isotope effects imply the exotic coupling mechanism in the iron-based superconductors.  相似文献   

11.
Highly conducting films of p-type CuCrO2 are attractive as hole-injectors in oxide-based light emitters. In this paper, we report on the development of dry etch patterning of CuCrO2 thin films. The only plasma chemistry that provided some chemical enhancement was Cl2/Ar under inductively coupled plasma conditions. Etch rates of ∼500 Å min−1 were obtained at chuck voltages around −300 V and moderate source powers. In all cases, the etched surface morphologies were improved relative to un-etched control samples due to the smoothing effect of the physical component of the etching. The threshold ion energy for the onset of etching was determined to be 34 eV. Very low concentrations (≤1 at.%) of residual chlorine were detected on the etched surfaces but could be removed by simple water rinsing.  相似文献   

12.
A novel green phosphor, Tb3+ doped Bi2ZnB2O7 was synthesized by conventional solid state reaction method. The phase of synthesized materials was determined using the XRD, DTA/TG and FTIR. The photoluminescence characteristics were investigated using spectrofluorometer at room temperature. Bi2ZnB2O7:Tb3+ phosphors excited by 270 nm and 485 nm wavelengths. The emission spectra were composed of three bands, in which the dominated emission of green luminescence Bi2ZnB2O7:Tb3+ attributed to the transition 5D4 → 7F5 is centered at 546 nm. The dependence of the emission intensity on the Tb3+ concentration for the Bi2−xTbxZnB2O7 (0.01 ≤ x ≤ 0.15) was studied and observed that the optimum concentration of Tb3+ in phosphor was 13 mol% for the highest emission intensity at 546 nm.  相似文献   

13.
The absorption spectrum of acetylene-d has been observed at high resolution between 6470 and 6630 cm−1 using an external cavity diode laser. Three cold bands have been observed: the strong 2ν1 band, the weaker ν1 + ν2 + 2ν5 band, and the (ν1 + ν3 + ν5)1 band, which gains its intensity through Coriolis resonance with 2ν1. Centers of unblended lines are determined with an accuracy of approximately 10 MHz.  相似文献   

14.
The rotationally resolved vibronic bands in the forbidden electronic transition of the cumulene carbene C3H2 have been observed in the gas phase by cavity ring down absorption spectroscopy through a supersonic planar plasma with allene as precursor. The band detected in the 16 223 cm−1 region is a result of vibronic interaction and is assigned to a combination of a1 and b2 vibrations with a frequency around 2250 cm−1. Another vibronic band near 15 810 cm−1 has an unusual rotational structure because the Ka = 0-1 subband is absent. It is assigned to a combination of a1 and b1 vibrations, ∼1850 cm−1, which borrow intensity from the near lying state due to a-type Coriolis coupling. A rotational analysis using a conventional Hamiltonian for an asymmetric top molecule yields molecular constants for the vibrational excited levels of the Ã1A2 state, which were used for the determination of the geometry. The stronger transition of C3H2, measured in a neon matrix in the 16 161-24 802 cm−1 range, was not detected. The reason for this is a short lifetime of the state, leading to line broadening.  相似文献   

15.
The impact of the ZrO2/La2O3 film thickness ratio and the post deposition annealing in the temperature range between 400 °C and 600 °C on the electrical properties of ultrathin ZrO2/La2O3 high-k dielectrics grown by atomic layer deposition on (1 0 0) germanium is investigated. As-deposited stacks have a relative dielectric constant of 24 which is increased to a value of 35 after annealing at 500 °C due to the stabilization of tetragonal/cubic ZrO2 phases. This effect depends on the absolute thickness of ZrO2 within the dielectric stack and is limited due to possible interfacial reactions at the oxide/Ge interface. We show that adequate processing leads to very high-k dielectrics with EOT values below 1 nm, leakage current densities in the range of 0.01 A/cm2, and interface trap densities in the range of 2-5 × 1012 eV−1 cm−2.  相似文献   

16.
C. Li 《Applied Surface Science》2010,256(22):6801-6804
Fe2O3/Al2O3 catalysts were prepared by solid state reaction method using α-Fe2O3 and γ-Al2O3 nano powders. The microstructure and surface properties of the catalyst were studied using positron lifetime and coincidence Doppler broadening annihilation radiation measurements. The positron lifetime spectrum shows four components. The two long lifetimes τ3 and τ4 are attributed to positronium annihilation in two types of pores distributed inside Al2O3 grain and between the grains, respectively. With increasing Fe2O3 content from 3 wt% to 40 wt%, the lifetime τ3 keeps nearly unchanged, while the longest lifetime τ4 shows decrease from 96 ns to 64 ns. Its intensity decreases drastically from 24% to less than 8%. The Doppler broadening S parameter shows also a continuous decrease. Further analysis of the Doppler broadening spectra reveals a decrease in the p-Ps intensity with increasing Fe2O3 content, which rules out the possibility of spin-conversion of positronium. Therefore the decrease of τ4 is most probably due to the chemical quenching reaction of positronium with Fe ions on the surface of the large pores.  相似文献   

17.
We studied the effect of hydrostatic pressure (P) on the structural phase transitions and superconductivity in the ternary and pseudo-ternary iron arsenides CaFe2As2, BaFe2As2, and (Ba0.55K0.45)Fe2As2, by means of measurements of electrical resistivity (ρ) in the 1.8-300 K temperature (T) range, pressures up to 20 kbar, and magnetic fields up to 9 T. CaFe2As2 and BaFe2As2 (lightly doped with Sn) display structural phase transitions near 170 and 85 K, respectively, and do not exhibit superconductivity in ambient pressure, while K-doped (Ba0.55K0.45)Fe2As2 is superconducting for T<30 K. The effect of pressure on BaFe2As2 is to shift the onset of the crystallographic transformation down in temperature at the rate of ~−1.04 K/kbar, while shifting the whole ρ(T) curves downward, whereas its effect on superconducting (Ba0.55K0.45)Fe2As2 is to shift the onset of superconductivity to lower temperatures at the rate of ~−0.21 K/kbar. The effect of pressure on CaFe2As2 is first to suppress the crystallographic transformation and induce superconductivity with onset near 12 K very rapidly, i.e., for P<5 kbar. However, higher pressures bring about another phase transformation characterized by reduced-resistivity, and the suppression of superconductivity, confining superconductivity to a narrow pressure dome centered near 5 kbar. Upper critical field (Hc2) data in (Ba0.55K0.45)Fe2As2 and CaFe2As2 are discussed.  相似文献   

18.
The rovibrational spectrum of the N2-N2O van der Waals complex has been recorded in the N2O ν1 region (∼1285 cm−1) using a tunable diode laser spectrometer to probe a pulsed supersonic slit jet. The observed transitions together with the data observed previously in the N2O ν3 region are analyzed using a Watson S-reduced asymmetric rotor Hamiltonian. The rotational and centrifugal distortion constants for the ground and excited vibrational states are accurately determined. The band-origin of the spectrum is determined to be 1285.73964(14) cm−1. A restricted two-dimensional intermolecular potential energy surface for a planar structure of N2-N2O has been calculated at the CCSD(T) level of theory with the aug-cc-pVDZ basis sets and a set of mid-bond functions. With the intermolecular distance fixed at the ground state value = 3.6926 Å, the potential has a global minimum with a well depth of 326.64 cm−1 at θN2 = 11.0° and θN2O = 84.3° and has a saddle point with a barrier height of 204.61 cm−1 at θN2 = 97.4° and θN2O = 92.2°, where θN2(θN2O) is the enclosed angle between the N-N axis (N-N-O axis) and the intermolecular axis.  相似文献   

19.
A new self-activated yellow-emitting Zn2V2O7 phosphor was synthesized by high temperature solid-state reaction. X-ray powder diffraction (XRD) analysis confirmed the sample with monoclinic formation of Zn2V2O7. The excitation and emission spectra indicated the phosphor can be efficiently excited by near ultraviolet (NUV) light in 220–400 nm range and exhibit a bright broad yellow emission with the highest emission intensity at 531 nm. The broad emission band from 400 to 650 nm can be attributed to the charge transfer transition in the VO4 tetrahedra, which suggests that the phosphor is a promising yellow phosphor applied for white light-emitting diodes (WLED).  相似文献   

20.
We present the high resolution absorption measurements of gaseous HONO at room temperature using continuous-wave cavity ring-down spectroscopy in the near-infrared region between 6017 and 6067 cm−1 at a resolution of 1 pm (0.037 cm−1). For the trans-HONO isomer an extensive analysis of the ν1+2ν3 combination band 6045.8089 cm-1 was performed starting from the results of a previous study for the 11 and 31 vibrational states [Guilmot J-M, Godefroid M, Herman M. Rovibrational parameters for trans-nitrous acid. J Mol Spectrosc 1993;160:387-400]. The present combination band is perturbed because of the existence of several dark states of HONO which could not be identified unambiguously. The rotational constants achieved for the 1132 state deviate slightly from the values which are predicted from the rotational constants achieved in the previous studies for the 11 and 31 vibrational states of trans-HONO.  相似文献   

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