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1.
The quadratic, cubic and semi-diagonal quartic force field of nitric acid has been calculated at the CCSD(T) level of theory employing a basis set of triple-ζ quality. A semi-experimental equilibrium structure has been derived from experimental ground state rotational constants and rovibrational interaction parameters calculated from the ab initio force field. It is found that the A and B semi-experimental equilibrium rotational constants of the 18O isotopologues (for which the rotation of principal axes is large) cannot be accurately reproduced. This problem is discussed and a remedy is proposed. Finally, the semi-experimental structure is in agreement with the ab initio structure calculated at the CCSD(T) level of theory using a basis set of at least quadruple-ζ quality and a core correlation correction, except for the long NO single bond for which the CCSD(T) value is too short due to inadequate treatment of electron correlation. The empirical structures are also determined and their accuracy is discussed. The best equilibrium structure is: re(NOsyn) = 1.209(1) Å, re(NOanti) = 1.194(1) Å, re(NO) = 1.397(1) Å, re(OH) = 0.968(1) Å, (ONOsyn) = 115.8(1)°, (ONOanti) = 114.2(1)° and (NOH) = 102.2(1)°.  相似文献   

2.
Monodeuterated diacetylene (HCCCCD) and its 13C-substituted species H13CCCCD, HC13CCCD, HCC13CCD, and HCCC13CD were investigated by Fourier transform microwave spectroscopy. The D nuclear quadrupole splittings were almost completely resolved. For H13CCCCD hyperfine splittings caused by the anisotropic nuclear spin-spin interaction between the H and 13C nuclei were also observed. The analysis yielded rotational constants, centrifugal distortion constants, and the constants for the nuclear quadrupole coupling and anisotropic nuclear spin-spin interaction. The substitution structure of HCCCCD was calculated as follows: rs(C-H) = 1.056054(39) Å, rs(CC) = 1.208631(4) Å, rs(C-C) = 1.374117(6) Å, rs(CC) = 1.208116(4) Å, and rs(C-D) = 1.056231(17) Å, in the order of the arrangement of the bonds. A rough estimate of the equilibrium structure is also presented. The eQq constant for the deuterium nucleus is 0.2061(4) MHz. The anisotropic 13C-H spin-spin interaction constant was experimentally determined for the first time as b = −29.2(15) kHz, which is defined as the coefficient of (3I2zI3z − I2 · I3), where I2 and I3 denote the H and 13C nuclear spins, respectively, and I2z and I3z their components along the molecular axis. The observed b constant is not accounted for by the direct magnetic dipole-dipole interaction only, suggesting a significant contribution from indirect anisotropic interaction.  相似文献   

3.
Magnesium oxide (MgO) nano-size powder is synthesized using magnesium nitrate hexahydrate and oxalic acid as precursors with ethanol as a solvent. The process involves gel formation, drying at 100 °C for 24 h to form magnesium oxalate dihydrate [α-MgC2O4·2H2O] and its decomposition at 500, 600, 800, and 1000 °C for 2 h to yield MgO powder (average crystallite size ∼6.5-73.5 nm). The sol-gel products at various stages of synthesis are characterized for their thermal behaviour, phase, microstructure, optical absorption, and presence of hydroxyl and other groups like OCO, CO, C-C, etc. MgO powder is shown to possess an f.c.c. (NaCl-type) structure with lattice parameter increasing with decrease in crystallite size (tav); typical value being ∼4.222(2) Å for tav∼6.5 nm as against the bulk value of 4.211 Å. Infrared absorption has shown MgO to be highly reactive with water. Also, a variety of F- and M-defect centres found in MgO produce energy levels within the band gap (7.8 eV), which make it attractive for application in plasma displays for increasing secondary electron emission and reducing flickering effects. The possible application of the intermediate sol-gel products, viz., α-MgC2O4·2H2O and anhydrous magnesium oxalate (MgC2O4) in understanding the plants and ESR dosimetry, respectively, has also been suggested.  相似文献   

4.
The Born-Oppenheimer (BO) equilibrium molecular structure () of cis-methyl formate has been determined at the CCSD(T) level of electronic structure theory using Gaussian basis sets of at least quadruple-ζ quality and a core correlation correction. The quadratic, cubic and semi-diagonal quartic force field in normal coordinates has also been computed at the MP2 level employing a basis set of triple-ζ quality. A semi-experimental equilibrium structure () has been derived from experimental ground-state rotational constants and the lowest-order rovibrational interaction parameters calculated from the ab initio cubic force field. To determine structures, it is important to start from accurate ground-state rotational constants. Different spectroscopic methods, applicable in the presence of internal rotation and used in the literature to obtain “unperturbed” rotational constants from the analysis and fitting of the spectrum, are reviewed and compared. They are shown to be compatible though their precision may be different. The and structures are in good agreement showing that, in the particular case of cis-methyl formate, the methyl torsion can still be treated as a small-amplitude vibration. The best equilibrium structure obtained for cis-methyl formate is: r(Cm-O) = 1.434 Å, r(O-Cc) = 1.335 Å, r(Cm-Hs) = 1.083 Å, r(Cm-Ha) = 1.087 Å, r(Cc-H) = 1.093 Å, r(CO) = 1.201 Å, (COC) = 114.4°, (CCHs) = 105.6°, (CCHa) = 110.2°, (OCH) = 109.6°, (OCO) = 125.5°, and τ(HaCOC) = 60.3°. The accuracy is believed to be about 0.001 Å for the bond lengths and 0.1° for the angles.  相似文献   

5.
The chemical preparation, the calorimetric studies and the crystal structure are given for two new organic sulfates NH3(CH2)5NH3SO4 1.5H2O (DAP-S) and NH3(CH2)9NH3SO4·H2O (DAN-S). DAP-S is monoclinic P21/n with unit cell dimensions: a=11.9330(2) Å; b=10.9290(2) Å; c=17.5260(2) Å; β=101.873(1)°; V=2236.77(6) Å3; and Z=8. Its atomic arrangement is described as inorganic layers of units and water molecules separated by organic chains. DAN-S is monoclinic P21/c with unit cell parameters: a=5.768(2) Å; b=25.890(10) Å; c=11.177(5) Å; β=115.70(4)°; V=1504.0(11) Å3 and Z=4. Its structure exhibits infinite chains, parallel to the [100] direction where the organic cations are interconnected. In both structures a network of strong and weak hydrogen bonds connects the different components in the building of the crystal.  相似文献   

6.
Polyimide (PMDA-ODA) surface was irradiated by low energy reactive atomic beam with energy 160-180 eV to enhance the adhesion with metal Cu film. O2+ and N2+ ions were irradiated at the fluence from 5 × 1015 to 1 × 1018 cm−2. Wetting angle 78° of distilled deionized (DI) water for bare PI was greatly reduced down to 2-4° after critical ion flounce, and the surface energy was increased from 37 to 81.2 erg/cm. From the analysis of O 1s core-level XPS spectra, such improvement seemed to result from the increment of hydrophilic carbonyl oxygen content on modified PI surface. To see more carefully correlation of the peel strength with interfacial reaction between Cu and PI, flexible copper clad laminate with Cu (9 μm)/Cu (200 nm) on modified PI substrate (25 μm) was fabricated by successive sputtering and electroplating. Firstly, peel strength was measured by using t-test and it was largely increased from 0.2 to 0.5 kgf/cm for Ar+ only irradiated PI to 0.72-0.8 kgf/cm for O2+ or N2O+ irradiated PI. Chemical reaction at the interface was reasoned by analyzing C 1s, O 1s, N 1s, and Cu 2p core-level X-ray photoelectron spectroscopy over the as-cleaved Cu-side and PI side surface through depth profiling. From the C 1s spectra of cleaved Cu-side, by the electron transfer from Cu to carbonyl oxygen, carbonyl carbon atom became less positive and as a result shifted to lower binding energy not reaching the binding energy of C2 and C3. The binding energy shift of the peak C4 as small as 1.7 eV indicates that carbonyl oxygen atoms were not completely broken. From the analysis of the O 1s spectra, it was found that new peak at 530.5 eV (O3) was occurred and the increased area of the peak O3 was almost the same with reduced area of the peak carbonyl oxygen peak O1. Since there was no change in the relative intensity of ether oxygen (O2) to carbonyl oxygen (O1), and thus O3 was believed to result from Cu oxide formation via a local bonding of Cu with carbonyl oxygen atoms. Moreover, from X-ray induced Auger emission spectra Cu LMM which was very sensitive to chemical bonding, Cu oxide or CuOC complex formation instead of CuNO complex was clearly identified by the observation of the peak at 570 eV at higher 2 eV than that of metal Cu. In conclusion, when Cu atoms were sputtered on modified PI by low energy ion beam irradiation, it can be suggested that two Cu atoms locally reacted with carbonyl oxygen in PMDA units and formed Cu+OC complex linkage without being broken from carbon atoms and thus the chemically bound Cu was in the form of Cu2O.  相似文献   

7.
The microwave spectra of monochloroamine (NH2Cl) and its isotopic species have been observed by Cazzoli et al. [G. Cazzoli, D.G. Lister, P.G. Favero, J. Mol. Spectrosc. 42 (1972) 286-295; G. Cazzoli, D.G. Lister, J. Mol. Spectrosc. 45 (1973) 467-474]. We observed microwave spectra of four isotopic species of 14NHD35Cl, 14NHD37Cl, 14ND235Cl, and 14ND237Cl produced by the direct reaction of ammonia gas-d3 or ammonium hydroxide-d5 with N-chlorosuccinimide. The microwave spectra of NHDCl (d1-species) and ND2Cl (d2-species) were observed in the frequency range from 8.0 to 60 GHz. The inversion splitting (ΔEo) of 14NHD35Cl and 14NHD37Cl in the ground vibrational state are shown to be 11.46(15) and 11.44(15) MHz for Ka = 0 ← 1, and 10.49(15) and 10.26(15) MHz for Ka = 1 ← 2, respectively. However, the inversion splitting of the d2-species could not be observed in our spectrometer. Only small J and K-dependence of the inversion splitting of d1-species was observed. The rotational constants of 14NHD35Cl were determined to be A = 187895.44(18), B = 13353.343(15) and C = 12859.794(15) MHz for the 0+ ← 0 state, which means the transition from the lower inversion level to the upper one, and A = 187918.52(18), B = 13353.345(15) and C = 12859.798(14) MHz for the 0 ← 0+ state. The rotational and centrifugal distortion constants of 14ND235Cl were determined to be A = 141030.885(72), B = 12594.481(6) and C = 12055.356(6) MHz, and ΔJ = 18.342(23), ΔJK = 318.15(56), ΔK = 2219.3 (fixed), δJ = 0.8717(17) and δK = 157.78(61) kHz. The values of the planar moments Pbb = (Ib − Ia − Ic)/2, of 14ND235Cl and 14ND237Cl were found to be 2.68898(2) and 2.68890(2) u Å2, respectively, which are about twice as large as those of normal species (Pbb = 1.3548(6) and 1.3544(16) u Å2, respectively). It was found that the bond length of r(N-Cl) of NH2Cl was longer than that of Cl-NCO by 0.045(12) Å, and was almost the same as that of CH2N-Cl, while it was much shorter than those of Cl-NO2 and Cl-NO, by 0.092(6) and 0.227(6) Å, respectively.  相似文献   

8.
The rotational spectra of nine isotopomers of dimethyl diselenide, CH3SeSeCH3, have been measured with a molecular-beam Fourier transform microwave spectrometer. The spectra were complex due to the presence of many isotopomers in natural abundance and the splitting caused by the interactions with two methyl internal rotors. The spectra were assigned and fit to experimental precision to an effective rotational Hamiltonian for molecules with two periodic internal motions. The spectra of the symmetric isotopomers are consistent with a C2 equilibrium structure. The rotational constants were used to determine the rs structure of the C-Se-Se-C frame with the results r(SeSe)=2.306(3) Å, r(SeC)=1.954(6) Å, ?(CSeSe)=99.8(2)°, ?(CSeSeC)=85.2(1)°. A barrier to internal rotation of the methyl groups of 395 ± 2 cm−1 was derived from the internal rotation splittings.  相似文献   

9.
Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) is applied to study NH3, adsorbed from the gas phase, and its decomposition products, i.e. NHx species, on Rh nanoparticles, produced by spincoating from a RhCl3 solution in water followed by reduction. A silicon ATR crystal with a hydroxilated SiO2 layer acts as the support for the nanoparticles. Upon exposure to NH3 in the vacuum chamber, NH3 adsorbed to both silica and Rh is detected (sensitivity ∼5 × 10−5 absorbance units). Interaction of the NH3 with the silica OH groups is observed around ∼2840 cm−1 in combination with peaks showing the disappearance of unperturbed OH vibrations between 3500 and 3700 cm−1. In addition, NH bend vibrations at 1634 cm−1 and NH stretch vibrations at 3065 and 3197 cm−1 are observed for substrate temperatures between 20 and 100 °C. The latter two correspond to NH on Rh, as verified with a sample without Rh, and probably correspond to undecomposed NH3. Moreover, they remain after evacuation, suggesting strongly bound species. For a substrate temperature of 75 and 100 °C, additional NH stretch peaks at 3354 and 3283 cm−1 are observed, possibly due to NH2 intermediates, indicating NH3 decomposition. It is shown that ATR-FTIR can contribute to the sensitive detection of adsorption and decomposition of gaseous species on realistic planar model catalysts.  相似文献   

10.
The synergistic effects of NH3 ambient and ultraviolet illumination on the dielectric properties of hafnia based gate dielectrics are reported in this paper. The films were processed at relatively low temperatures (∼400 °C) by pulsed laser ablation and UV oxidation technique. UV illumination and the NH3 ambient created a thin and a denser interfacial layer (at the film-Si interface) comprised of HfSiON bonding. As a result of the interfacial layer modification, a leakage current density lower than 10−4 A/cm2 and a dielectric constant of ∼21.7 were extracted from the best samples processed in NH3 and under UV illumination. The nitrogen doped HfO2 also exhibited a thinner interfacial layer (∼12 Å) in comparison to the films processed without NH3 ambient.  相似文献   

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