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1.
The transient thiophosphenous fluoride FPS was produced by pyrolysis of 2.5% F2PSPF2 in Ar at 1300–1800°C. High-resolution (≥0.004 cm−1) Fourier transform infrared spectra of the a-type ν1 and b-type ν2 bands, centered respectively at 803.249 and 726.268 cm−1, were measured and fitted to rotational and quartic centrifugal distortion parameters. The millimeter-wave spectrum, essentially b-type, was measured between 300 and 370 GHz in the ground state and in the ν3 excited state for FP32S and in the ground state for FP34S. The frequencies were fitted to a Watson-type A-reduced Hamiltonian up to sextic distortion terms. High level ab initio calculations with large basis sets were performed on FPS and supported the first identification of its infrared and millimeter wave spectra. The calculated anharmonic force field provided precise ab initio rovibrational α constants which were combined with the experimental molecular parameters to determine an accurate equilibrium structure of the molecule: re(PS)=188.86 pm, re(PF)=158.70 pm, θ(FPS)=109.28°. The collision-controlled 1/e lifetime measured in a 10-Pa (1 : 20) F2PSPF2/Ar mixture was 2 s, more than two orders of magnitude larger than that of FPO under the same experimental conditions.  相似文献   

2.
High-resolution (0.001 cm−1) coherent anti-Stokes Raman scattering (CARS) was used to observe the Q-branch structure of the IR-inactive ν1 symmetric stretching mode of 32S16O3 and its various 18O isotopomers. The ν1 spectrum of 32S16O3 reveals two intense Q-branches in the region 1065–1067 cm−1, with surprisingly complex vibrational–rotational structure not resolved in earlier studies. Efforts to simulate this with a simple Fermi-resonance model involving ν1 and 2ν4 states do not reproduce the spectral detail, nor do they yield reasonable spectroscopic parameters. A more subtle combination of Fermi resonance and indirect Coriolis interactions with nearby states, 2ν4(1=0, ±2), ν24(1=±1), 2ν2(1=0), is suspected and a determination of the location of these coupled states by high-resolution infrared measurements is under way. At medium resolution (0.125 cm−1), the infrared spectra reveal Q-branch features from which approximate band origins are estimated for the ν2, ν3, and ν4 fundamental modes of 32S18O3, 32S18O216O, and 32S18O16O2. These and literature data for 32S16O3 are used to calculate force constants for SO3 and a comparison is made with similar values for SO2 and SO. The frequencies and force constants are in excellent agreement with those obtained by Martin in a recent ab initio calculation.  相似文献   

3.
By using resonance-enhanced two-photon ionization, rotationally resolved spectra of the 610 band of 12C6D6 and (13C12C5D6 molecules have been obtained for the first time at a rotational temperature of 0.7 K in a pulsed supersonic beam. From the former, the values of B″ = 0.1573 ± 0.0008 cm−1, B′ = 0.1508 ± 0.0008 cm−1, and ξ′ = −0.412 ± 0.050 have been derived for rotational and Coriolis constants in the lower and upper levels of 12C6D6. Also, the spectra corresponding to 12C6H6 and 13C12C5H6 have been measured and the values B″ = 0.1892 ± 0.0008 cm−1, B′ = 0.1815 ± 0.0008 cm−1, and ξ′ = −0.586 ± 0.050 have been obtained for 12C6H6, in agreement with previous results. Rotational constants of 13C labeled benzene molecules have been geometrically deduced from the constants obtained. Experimental isotopic shifts of the vibronic origins of the 6a10 and 6b10 bands have been determined. There is agreement with previous 13C-benzene-h6 data. The present results are −0.91 ± 0.05 and 3.09 ± 0.05 cm−1 for 13C12C5D6 and −1.64 ± 0.05 and 2.64 ± 0.05 cm−1 for 13C12C5H6. The splittings of vibrational modes 6b and 6a in the 1B2u state are 4.00 ± 0.10 cm−1 for 13C12C5D6 and 4.28 ± 0.10 cm−1 for 13C12C5H6.  相似文献   

4.
The high-resolution infrared spectrum of HCF3 was studied in the ν6 fundamental (near 500 cm−1) and in the 2ν6 overtones (near 1000 cm−1) regions. The present study reports on the analysis of the hot bands in the ν6 region, as well as the first observation and assignment of the 2ν62 perpendicular band. Using ν6, 2ν6±2ν6±1 and 2ν62 experimental wavenumbers, accurate coefficients C0 and DK0 of the K-dependent ground-state energy terms were obtained, using the so-called “loop method.” Ground-state energy differences Δ(K,J)=E0(K,J)−E0(K−3,J) were obtained for K=3–30. A least-squares fit of 81 such differences gave the following results (in cm−1): C0=0.1892550(15); DK0=2.779(26) × 10−7.  相似文献   

5.
This paper reports the spectral properties and energy levels of Cr3+:Sc2(MoO4)3 crystal. The crystal field strength Dq, Racah parameter B and C were calculated to be 1408 cm−1, 608 cm−1 and 3054 cm−1, respectively. The absorption cross sections σα of 4A24T1 and 4A24T2 transitions were 3.74×10−19 cm2 at 499 nm and 3.21×10−19 cm2 at 710 nm, respectively. The emission cross section σe was 375×10−20 cm2 at 880 nm. Cr3+:Sc2(MoO4)3 crystal has a broad emission band with a broad FWHM of 176 nm (2179 cm−1). Therefore, Cr3+:Sc2(MoO4)3 crystal may be regarded as a potential tunable laser gain medium.  相似文献   

6.
The absorption spectrum of carbon dioxide in natural isotopic abundance has been investigated by CW-cavity ring down spectroscopy with a new setup based on fibred distributed feedback (DFB) laser diodes. By using a series of 25 DFB lasers, the CO2 spectrum was recorded in the 7123–7793 cm−1 region with a typical sensitivity of 3×10−10 cm−1. A 2125 transitions with intensities as low as 1×10−29 cm/molecule were detected and assigned to the 12C16O2, 16O12C17O and 16O12C18O isotopologues. For comparison, only 357 of them were previously reported from Venus spectra and 344 transitions were included in the 2004 version of the HITRAN database. The band by band analysis has led to the determination of the rovibrational parameters of 28, 2 and 6 bands for the 12C16O2, 16O12C17O and 16O12C18O isotopologue, respectively. While the uncertainty on the experimental line positions is on the order of 5×10−4 cm−1, the average deviation from the 12C16O2 calculated values provided by the most recent version of the carbon dioxide spectroscopic databank (CDSD) is −2.8×10−3 cm−1 with an root mean square (rms) deviation of 3.5×10−3 cm−1. Maximum deviations in the order of 0.02 and 0.12 cm−1 were evidenced for some bands of the 16O12C17O and 16O12C18O minor isotopologues. The obtained results improve significantly the previous measurements from Venus spectra and will be valuable to refine the sets of effective Hamiltonian parameters used to generate the CDSD database.  相似文献   

7.
We present two new sensitivity enhanced gradient NMR experiments for measuring interference effects between chemical shift anisotropy (CSA) and dipolar coupling interactions in a scalar coupled two-spin system in both the laboratory and rotating frames. We apply these methods for quantitative measurement of longitudinal and transverse cross-correlation rates involving interference of 13C CSA and 13C–1H dipolar coupling in a disaccharide, α,α- -trehalose, at natural abundance of 13C as well as interference of amide 15N CSA and 15N–1H dipolar coupling in uniformly 15N-labeled ubiquitin. We demonstrate that the standard heteronuclear T1, T2, and steady-state NOE autocorrelation experiments augmented by cross-correlation measurements provide sufficient experimental data to quantitatively separate the structural and dynamic contributions to these relaxation rates when the simplifying assumptions of isotropic overall tumbling and an axially symmetric chemical shift tensor are valid.  相似文献   

8.
We propose a review of quantitative spectroscopy of polyynes in the infrared and ultraviolet domain focusing on essential spectroscopic parameters for the interpretation of observed spectra in the infrared and ultraviolet domain and for photochemical modeling. We point at the lacking data in both wavelength domains for C2H2, C4H2, C6H2, C8H2 and propose downloadable files of the ultraviolet absorption coefficient ready to use for photolysis rate calculations. For longer polyynes, we calculate extrapolated ultraviolet spectra and calculate their photolysis rate. Using a simplified photochemical model of the polyynes in Titan and CRL618, we predict their relative abundance and compare them with the observed ones. This also leads us to predict the abundances of the longer polyynes.  相似文献   

9.
Nonlinear optical properties of Fe2O3 nanoparticles were investigated by the signal-beam Z-scan technique with Ar+ and Ne–He lasers. The largest reported effective nonlinear coefficient, n2=−8.07×10−7 cm2/W, was obtained. It is demonstrated that the nonlinear optical response originals from quantum confinement effect.  相似文献   

10.
A pyrochlore-related Ce2Zr2O8−x phase has been prepared in a reduction reoxidation process from Ce0.5Zr0.5O2 powders. Ce2Zr2O8−x, based on a cubic symmetry with a=1.053 nm, decomposes in nitrogen at 800 °C, but remains stable up to 900 °C in air. It shows mixed oxygen ionic and electronic conductivity. The bulk conductivity at 700 °C is 4×10−4 S cm−1 in air and 1×10−2 S cm−1 in nitrogen, and the activation energy is 1.27 eV in air. In nitrogen, the Arrhenius law is not obeyed, and a curved plot was obtained from 400 to 700 °C; then, the conductivity decreased rapidly due to the thermal decomposition of Ce2Zr2O8−x.  相似文献   

11.
The glasses with the composition of 37.5Li2O–(25 − x)Fe2O3xNb2O5–37.5P2O5 (mol%) (x = 5,10,15) are prepared, and it is found that the addition of Nb2O5 is effective for the glass formation in the lithium iron phosphate system. The glass–ceramics consisting of Nasicon-type Li3Fe2(PO4)3 crystals with an orthorhombic structure are developed through conventional crystallization in an electric furnace, showing electrical conductivities of 3 × 10− 6 Scm− 1 at room temperature and the activation energies of 0.48 eV (x = 5) and 0.51 eV (x = 10) for Li+ ion conduction in the temperature range of 30–200 °C. A continuous wave Nd:YAG laser (wavelength: 1064 nm) with powers of 0.14–0.30 W and a scanning speed of 10 μm/s is irradiated onto the surface of the glasses, and the formation of Li3Fe2(PO4)3 crystals is confirmed from XRD analyses and micro-Raman scattering spectra. The crystallization of the precursor glasses is considered as new route for the fabrication of Li3Fe2(PO4)3 crystals being candidates for use as electrolyte materials in lithium ion secondary batteries.  相似文献   

12.
The accurate measurement of small spin–spin coupling constants in macromolecules dissolved in a liquid crystalline phase is important in the context of molecular structure investigation by modern liquid state NMR. A new spin-state-selection filter, DIPSAP, is presented with significantly reduced sensitivity to J-mismatch of the filter delays compared to previously proposed pulse sequences. DIPSAP presents an attractive new approach for the accurate measurement of small spin–spin coupling constants in molecules dissolved in anisotropic solution. Application to the measurement of 15N–13C′ and 1HN13C′ coupling constants in the peptide planes of 13C, 15N labeled proteins demonstrates the high accuracy obtained by a DIPSAP-based experiment.  相似文献   

13.
A new two-dimensional pulse sequence for T2* measurement of protons directly coupled to 13C spins is proposed. The sequence measures the tranverse relaxation time of heteronuclear proton single-quantum coherence under conditions of free precession and is therefore well suited to evaluate relaxation losses of proton magnetization during preparation delays of heteronuclear pulse experiments in analytical NMR. The relevant part of the pulse sequence can be inserted as a “building block” into any direct or inverse detecting H,C correlation pulse sequence if proton spin–spin relaxation is to be investigated. In this contribution, the building block is inserted into a HETCOR as well as into a HMQC pulse sequence. Experimental results for the HETCOR-based sequence are given.  相似文献   

14.
Amino acid type-selective experiments can help to remove ambiguities in automated assignment procedures for 15N/13C-labeled proteins. Here we present five triple-resonance experiments that yield amino acid type-selective 1H–15N correlations for aromatic amino acids. Four of the novel experiments are based on the MUSIC coherence transfer scheme that replaces the initial INEPT transfer and is selective for CH2. The MUSIC sequence is combined with selective excitation pulses to create experiments for Trp (W-HSQC) as well as Phe, Tyr, and His (FYH-HSQC). In addition, an experiment selective for Trp H1–N1 is presented. The new experiments are recorded as two-dimensional experiments and their performance is demonstrated with the application to a protein domain of 115 amino acids.  相似文献   

15.
This paper is devoted to the third part of the analysis of the very weak absorption spectrum of the 18O3 isotopologue of ozone recorded by CW-Cavity Ring Down Spectroscopy between 5930 and 6900 cm−1. In the two first parts [A. Campargue, A. Liu, S. Kassi, D. Romanini, M.-R. De Backer-Barilly, A. Barbe, E. Starikova, S.A. Tashkun, Vl.G. Tyuterev, J. Mol. Spectrosc. (2009), doi: 10.1016/j.jms.2009.02.012 and E. Starikova, M.-R. De Backer-Barilly, A. Barbe, Vl.G. Tyuterev, A. Campargue, A.W.Liu, S. Kassi, J. Mol. Spectrosc. (2009) doi: 10.1016/j.jms.2009.03.013], the effective operators approach was used to model the spectrum in the 6200–6400 and 5930–6080 cm−1 regions, respectively. The analysis of the whole investigated region is completed by the present investigation of the 6490–6900 cm−1 upper range. Three sets of interacting states have been treated separately. The first one falls in the 6490–6700 cm−1 region, where 1555 rovibrational transitions were assigned to three A-type bands: 3ν2 + 5ν3, 5ν1 + ν2 + ν3 and 2ν1 + 3ν2 + 3ν3 and one B-type band: ν1 + 3ν2 + 4ν3. The corresponding line positions were reproduced with an rms deviation of 18.4 × 10−3 cm−1 by using an effective Hamiltonian (EH) model involving eight vibrational states coupled by resonance interactions. In the highest spectral region – 6700–6900 cm−1 – 389 and 183 transitions have been assigned to the ν1 + 2ν2 + 5ν3 and 4ν1 + 3ν2 + ν3 A-type bands, respectively. These very weak bands correspond to the most excited upper vibrational states observed so far in ozone. The line positions of the ν1 + 2ν2 + 5ν3 band were reproduced with an rms deviation of 7.3 × 10−3 cm−1 by using an EH involving the {(054), (026), (125)} interacting states. The coupling of the (431) upper state with the (502) dark state was needed to account for the observed line positions of the 4ν1 + 3ν2 + ν3 band (rms = 5.7 × 10−3 cm−1).The dipole transition moment parameters were determined for the different observed bands. The obtained set of parameters and the experimentally determined energy levels were used to generate a complete line list provided as Supplementary Materials.The results of the analyses of the whole 5930–6900 cm−1 spectral region were gathered and used for a comparison of the band centres to their calculated values. The agreement achieved for both 18O3 and 16O3 (average difference on the order of 1 cm−1) indicates that the used potential energy surface provides accurate predictions up to a vibrational excitation approaching 80% of the dissociation energy. The comparison of the 18O3 and 16O3 band intensities is also discussed, opening a field of questions concerning the variation of the dipole moments and resonance intensity borrowing by isotopic substitution.  相似文献   

16.
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   

17.
To understand the surprising behavior between the variations of the P′–P–P″ angles and the correlated variations of the O′–P–O″ ones, two lithium cyclohexaphosphate compounds Li6P6O18·3H2O and Li6P6O18 are studied by solid state nuclear magnetic resonance (NMR) spectroscopy. The two compounds exhibit the same [P6O18]6− ring anions but with 3m or internal symmetry, respectively. Such symmetries induce local distortions that are exhibited by NMR spectroscopy. One-dimensional (1D) NMR gives information on structural sites of 7Li and 31P ions and the crystallographic non-equivalencies are observed. Nevertheless, in the anhydrous compound, X-ray diffraction and NMR results do not completely agree and some discrepancy exists between the number of sites observed with the first technique and the number of lines exhibited in the NMR spectra either for 7Li or 31P nuclei. This problem is elucidated by using 2D double quantum NMR spectroscopy coupled with theoretical considerations. We find that the 31P chemical shift tensor is dependent on the deviations of the O–P–O angles from those in the regular tetrahedron. Within the same empirical model, we suggest that the surprising behavior between the variations of the P′–P–P″ and the ones of the O′–P–O″ is related to the overall charge on the PO4 group. We also find the positions of the isotropic lines for 7Li essentially depend on the site co-ordination of this nuclei.  相似文献   

18.
The infrared (IR) spectrum of PD3 has been recorded in the 1580–1800 cm−1 range at a resolution of 0.0027 cm−1. About 2400 rovibrational transitions with J=K22 have been measured and assigned to the ν1 (A1) and ν3 (E) stretching fundamentals. These include 506 “perturbation-allowed” transitions with selection rules Δ(kl)=±3. Splittings of the K′′=3 lines have been observed. Effects of strong perturbations are evident in the spectrum. Therefore the rovibrational Hamiltonian adopted for the analysis explicitly takes into account the Coriolis and k-type interactions between the v1=1 and v3=1 states, and includes also several essential resonances within these states. The rotational structure in the v1=1 and v3=1 vibrational states up to J=K=18 was reproduced by fitting simultaneously all experimental data. Thirty-four parameters reproduced 1950 transitions retained in the final cycle with a standard deviation of the fit equal to 4.9 × 10−4 cm−1 (about the precision of the experimental measurements).  相似文献   

19.
This study investigates the effects of developmental stage and muscle type on the mobility and distribution of water within skeletal muscles, using low-field 1H-NMR transverse relaxation measurements in vitro on four different porcine muscles (M. longissimus dorsi, M. semitendinosus, M. biceps femoris, M. vastus intermedius) from a total of 48 pigs slaughtered at various weight classes between 25 kg and 150 kg. Principal component analysis (PCA) revealed effects of both slaughter weight and muscle type on the transverse relaxation decay. Independent of developmental stage and muscle type, distributed exponential analysis of the NMR T2 relaxation data imparted the existence of three distinct water populations, T2b, T21, and T22, with relaxation times of approximately 1–10, 45–120, and 200–500 ms, respectively. The most profound change during muscle growth was a shift toward faster relaxation in the intermediate time constant, T21. It decreased by approx. 24% in all four muscle types during the period from 25 to 150 kg live weight. Determination of dry matter, fat, and protein content in the muscles showed that the changes in relaxation time of the intermediate time constant, T21, during growth should be ascribed mainly to a change in protein content, as the protein content explained 77% of the variation in the T21 time constant. Partial least squares (PLS) regression revealed validated correlations in the region of 0.58 to 0.77 between NMR transverse relaxation data and muscle development for all the four muscle types, which indicates that NMR relaxation measurements may be used in the prediction of muscle developmental stage.  相似文献   

20.
Bis-alkynylated oligoethyleneglycol (OEG) and a monopropargyl-functionalized perfluorinated ethylene glycol (FEG) were clicked to azide-functionalized gold surface (Au–N3) at room temperature via the well known 1,3 cycloaddition click chemical reaction. The Au–N3 substrate was obtained by nucleophilic attack of NaN3 on gold substrates modified by the electrochemical reduction of the , +N2–C6H4–CH2Br diazonium salt. This electrochemical process yields aryl layer-modified gold of the type Au–C6H4–CH2Br (hereafter Au–Br). The untreated and modified gold plates were examined by XPS, PMIRRAS and contact angle measurements. XPS brought evidence for electrografting aryl layers by the detection of Br3d; azide functionalization by the increase of the N/Br atomic ratio; and click reaction of OEG with Au–N3 by the increase of O/N ratio. In addition, the perfluorinated plate (Au-FEG) exhibited F1s and characteristic C1s peaks from -(CF2)7- chain and terminal CF3. Infra red spectroscopy (PMIRRAS) evidenced (i) grafting N3 to Au–Br; (ii) characteristic stretching bands, from ethylene glycol units, C–O–C (1100–1300 cm−1); CF2 (1000–1100 cm−1) and CF3 (1100–1350 cm−1) from FEG grafts; and (iii) suppression of alkynyl bands from OEG and FEG after surface click chemistry. More importantly, PMIRRAS results support an important bridging of the bispropargyl oligoethylene glycol at the gold surface. Water drop contact angles were found to be 48.7° and 83.0° for Au-OEG and Au-FEG, respectively, therefore highlighting the control over the hydrophilic/hydrophobic character of the clicked substrate.This work shows that clicking macromolecules to grafted, diazonium salt-derived aryl layers is a novel, simple and valuable approach for designing robust, functional surface organic coatings.  相似文献   

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