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1.
The convergence of ab initio calculations of the beryllium dimer potential is examined with several basis sets orders of perturbation theory. When the atomic pair natural orbital basis set calculations are extrapolated to the complete basis set and full CI limits, the calculated parameters: Re=2.447 Å, De=827 cm −1, ν 01=212.7 cm −1, ν 12=167.2 cm −1, ν 23=121.5 cm −1 and ν 34=77.7 cm −1 are in good agreement with the experimental parameters: Re=2.45 Å, De=839±10 cm −1, ν 01=223.2 cm −1, ν 12=169.7 cm −1, ν 23=122.5 cm −1, and ν 34=79 cm −1. 相似文献
2.
Medium-resolution spectra of the N 2 b 1Π u-X 1Σ g+ band system were recorded by 1 + 1 multiphoton ionization. In the spectra we found different linewidths for transitions to different vibrational levels in the b 1Π u state: Δν 0 = 0.50 ± 0.05 cm −1, Δν 1 = 0.28 ± 0.02 cm −1, Δν 2 = 0.65 ± 0.06 cm −1, Δν 3 = 3.2 ± 0.5 cm −1, Δν 4 = 0.60 ± 0.07 cm −1, and Δν 5 = 0.28 ± 0.02 cm −1. From these linewidths, predissociation lifetimes τ ν were obtained: τ 0 = 16 ± 3 ps, τ 1 > 150 ps, τ 2 = 10 ± 2 ps, τ 3 = 1.6 ± 0.3 ps, τ 4 = 9 ± 2 ps, and τ 5 > 150 ps. Band origins and rotational constants for the b 1Π uν = 0 and 1 levels were determined for the 14N 2 and 14N 15N molecules. 相似文献
3.
High resolution vibration-rotation spectra of 13C 2H 2 were recorded in a number of regions from 2000 to 5200 cm −1 at Doppler or pressure limited resolution. In these spectral ranges cold and hot bands involving the bending-stretching combination levels have been analyzed up to high J values. Anharmonic quartic resonances for the combination levels ν 1 + mν 4 + nν 5, ν 2 + mν 4 + ( n + 2) ν 5 and ν 3 + ( m − 1) ν 4 + ( n + 1) ν 5 have been studied, and the l-type resonances within each polyad have been explicitly taken into account in the analysis of the data. The least-squares refinement provides deperturbed values for band origins and rotational constants, obtained by fitting rotation lines only up to J ≈ 20 with root mean square errors of ≈ 0.0003 cm −1. The band origins allowed us to determine a number of the anharmonicity constants xij0. 相似文献
4.
We have previously determined an analytical ab initio six-dimensional potential energy surface for the HCl dimer, and in the present paper we use this potential, with the HCl bond lengths held fixed, in a full (four-dimensional) close-coupling calculation to determine the energies of the lowest 24 vibrational states. These vibrational states involve the intermolecular stretch ν 4, the trans-bend tunneling vibration ν 5, and the torsion ν 6. The highest of the 24 levels is the (ν 4ν 5ν 6)=(111) state, for which we calculate an energy of 200 cm −1 above the (000) state. As well as determining tunneling energies up to 5ν 5=183 cm −1, we determine ν 4=49 cm −1, 2ν 4=93 cm −1, 3ν 4=134 cm −1, 4ν 4=172 cm −1, ν 6=137 cm −1 and ν 4+ν 6=178 cm −1, together with tunneling energies in all these states. Making allowance for the HCl stretching zero-point energy we determine the dissociation energy D0 as 390 cm −1 on this analytical surface. We determine that below 300 cm −1 there are 72 vibrational ( J=K=0) states, and below dissociation there are 162 vibrational ( J=K=0) states, for this potential surface. 相似文献
5.
The vibrational spectrum of Sb 4O 6 in the gas phase has been measured at 1000 K by high-temperature infrared spectroscopy. The four infrared-active absorption bands were observed at ν 7 = 785.0 cm 1, ν 8 = 176.2 cm −1, ν 9 = 292.4 cm −1 and ν 10 = 415.6 cm −1. By combining these results with data on the molecular geometry and the infrared-inactive modes, as reported in the literature, the thermodynamic functions of Sb 4O 6 have been calculated. 相似文献
6.
We have recorded and analyzed the molecular beam spectra of allene in the regions of the ν 1 + ν 5 and 2 ν 8 bands around 5947.5 and 6135.5 cm −1, respectively. The ν 1 + ν 5 band only shows minor perturbations and we suspect the presence of a doorway state that causes parallel Coriolis coupling to the bath states. Perpendicular Coriolis interactions do not seem to play an important role since the size of the matrix elements does not increase systematically with J′. The spectrum in the region of the 2 ν 8 band is more complicated; a total of six sub-bands has been identified with K = 0–2. Based on the lack of any systematic dependence on J′ and an inverse dependence of the coupling on K, we expect that neither parallel nor perpendicular Coriolis coupling is present in this band. The effective lifetime for both bands is calculated to be about 200 ps, which is very similar to the lifetimes of an acetylenic C---H stretch overtone. 相似文献
7.
The high-resolution infrared absorption spectrum of an equilibrium mixture of HCN and HCl in a static gas long-path absorption cell is recorded in the 2500–2900 cm −1 spectral region at 205 K. The spectrum shows rovibrational structure which has the typical appearance of a parallel band of a linear molecule and is assigned to the intramolecular H–Cl stretching vibration band ν 2 of the linear HCN–H 35Cl heterodimer. The rovibrational analysis of the band yield a band origin ν 0 of 2779.0968(12) cm −1 together with a value for the upper-state rotational constant B′ of 0.067722(2) cm −1. The observed red shift of 107 cm −1 for the ν 2 band of HCN–H 35Cl relative to the H–Cl stretching vibration band of monomer H 35Cl is in excellent agreement with results from the MP2/6−311++G** level of theory. The value of the upper-state rotational constant shows that the intermolecular hydrogen bond shortens by 0.022 Å upon intramolecular vibrational excitation of the ν 2 mode. 相似文献
8.
Large-scale CEPA-1 calculations have been carried out for linear C 5, a molecule of substantial interest to combustion processes and astrochemistry. The equilibrium bond lengths are predicted to be 1.289 Å (outer CC bond) and 1.283 Å (inner CC bond), with an accuracy of 0.002 Å. The calculated ν 3 band origins of 2161 cm −1 (105 CGTO basis) and 2137 cm −1 (150 CGTO basis) are in good agreement with the experimental value of 2169 cm −1. This band has an extremely large transition moment of 0.74 D. The less intense stretching fundamental ν 4 (μ=0.18 D) is predicted to occur at 1478 ± 10 cm −1. Predictions for the totally symmetric stretching and the bending vibrational frequencies (in cm −1) are 2008 (1σ g+), 792 (2σ g+), 570 (1π u), 209 (1π g) and 119 (2π u). 相似文献
9.
Infrared spectroscopy and matrix isolation technique have been used to study the 1 : 1 complexes formed between 2,4,5-trichlorophenol (TCP), pentachlorophenol (PCP) or 2-chloro-4,6-dinitrophenol (CNP) and trimethylamine (TMA) isolated in solid argon. The results were analyzed in relation to the type of complex formed. Depending on the proton-donor ability of the phenol three different types of hydrogen bonded complexes have been identified in argon matrices. The weakest phenol in the series, TCP (p Ka = 6.72), forms a strong molecular hydrogen bonded complex with TMA as indicated by the broad ν(OHN) absorption with a maximum at 2490 cm −1 and a band at 811 cm −1 due to the ν s(C 3N) mode of the perturbed amine. The strongest phenol, CNP (p Ka = 2.01), interacts with TMA in an argon matrix to form ionic complex with the proton transferred to the base molecule. This is evidenced by the presence of the ν(NH +---O −) absorption between 3000−1800 cm −1, by the ν as(C 3N +) and ν s(C 3N +) absorptions due to the protonated amine and by numerous product bands due to the relatively strongly perturbed modes of the phenol ring. The interaction between TMA and a phenol of intermediate strength, PCP (p Ka = 4.74), in solid argon probably leads to the formation of two types of hydrogen bonded complexes: an ionic complex with the proton transferred to the amine molecule and a pseudosymmetric one with the proton more or less equally shared between the phenol and amine molecules. In this case the protonic absorption consists of two broad features situated in the 3000–1600 cm −1 and 950–400 cm −1 regions due to the ν(NH +O −) and ν(OHN) modes, respectively. 相似文献
10.
Accurate electric dipole moment functions have been calculated for the stretching vibrational coordinates of the linear molecules HCN, HNC, HCCF and HC 3N by means of coupled cluster theory with single and double excitation operators plus a quasi-perturbative treatment of connected triples (CCSD(T)). Combining these with anharmonic stretching vibrational wave-functions absolute IR intensities for strecthing vibrational transitions up to high overtones are obtained. For HCN, excellent agreement with experiment is observed up to 7 ν 1 + η 3 at 23047 cm −1. HCCF and DCCF show unusual behavior, with the ν 2 band with origin at 2239.2 cm −1 being strongest in HCCF and the ν 1 band with origin at 2645.1 cm −1 being the most intense in DCCF. The Fermi resonance system 2ν 3/ν 2 of DCCF is analysed in detail. The calculated IR intensities of the stretching fundamentals of HC 3N and DC 3N, which are difficult to obtain with high accuracy, are in very good agreement with the existing experimental data. 相似文献
11.
The infrared absorption of mixtures of dimethyl ether and hydrogen halide (HX) in nitrogen at 13 K display relatively narrow bands in the range 650–800 cm −1 with an isotopic ratio ν H/ν D larger than 1.4 and weakly halogen dependent; these features are assigned to the antisymmetric O…H…O stretching within the [(CH 3) 2 O…H…O(CH 3) 2] +X − ion pair. With HI—ether mixtures, the intensity of the 660 cm −1 band decreases under infrared irradiation of the matrix, which might be due to the transfer of the proton back to the I − anion. 相似文献
12.
A 2 MHz resolution electric-resonance optothermal spectrometer and a microwave-sideband CO 2 laser have been used with microwave-infrared double resonance to investigate high-order torsional couplings in the 10 μm infrared spectrum of 3,3,3-trifluoropropene. Three normal mode vibrations are studied with band origins at 963.4, 980.2 and 1025.2 cm −1. The 963.4 cm −1 band is well characterized by an asymmetric-top Hamiltonian, except for the presence of a weak perturbation for J′ = 7, Ka′ = 2 affecting only the A-symmetry internal-rotor state. Microwave-infrared double resonance is used to study the microwave spectrum of the perturbing or ‘dark’ state. The observed dark-state K-doublet asymmetry splittings and rotational-state selection rules indicate that the perturbing state has five quanta of excitation in the torsional mode (ν 21) built upon the A″ ν 19 fundamental. The precise frequency determined for 5 β 21 of 421(2) cm −1 leads to the first accurate determination of the barrier to CF 3 internal rotation as 641(5) cm −1. In contrast to the 963.4 cm −1 vibration, the 980.2 and 1025.2 cm −1 modes show a large number of J′ and Ka′ perturbations which differentially affect the A and E symmetry internal-rotor states. The magnitude of the perturbation-induced A/E splittings indicate that the perturbing states must have at least four quanta of torsional excitation. The present results suggest that high-order vibrational interactions are important in the vibrational dynamics of molecules at low levels of overall vibrational excitation. 相似文献
13.
Four novel tetranuclear macrocyclic complexes of the formula [(CuL i) 3Fe](ClO 4) 3·3H 2O ( i=1–4, L i are the dianions of the [14]N 4 and [15]N 4 macrocyclic oxamides, namely 2,3-dioxo-5,6:13,14-dibenzo-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene, 2,3-dioxo-5,6:13,14-dibenzo-9-methyl-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene and 2,3-dioxo-5,6:14,15-dibenzo-7,13-bis(ethoxycarbonyl)-1,4,8,12-tetraazacyclotetradeca-7,12-diene] have been prepared and characterized. These complexes are the first examples of oxamido-bridged Cu(II)–Fe(III) heterometallic species. Cryomagnetic studies on [(CuL 1) 3Fe](ClO 4) 3·3H 2O (1) and [(CuL 3) 3Fe](ClO 4) 3·3H 2O (3) (77–300 K) revealed that the Cu(II) and Fe(III) ions interact antiferromagnetically through the oxamido bridge, with the exchange integral J=−30.8 cm −1 for 1 and J=−28.7 cm −1 for 3 based on
. The interaction parameters have been compared with that of the related [Cu 3Mn] compound. 相似文献
14.
Fluorescence and Raman scattering were observed from Pb 2 isolated in neon and argon matrices. Two new excited states were observed by two-photon stepwise excitations, which involve low-lying electronic states of Pb 2. Most spectroscopic constants of the states observed could be given and complement previous results. Two resonance Raman progressions with ω c = 112.5 and 123.1 cm −1 and a single Raman signal at 80 cm −1 were observed in argon matrices. The ω c = 123.1 cm −1 Raman signal which had recently been assigned to a larger Pb cluster was shown to arise from Raman scattering within the electronically excited A state of Pb 2 at 5500 cm −1. 相似文献
15.
The microwave spectrum of ethyl fluoroformate displays strong a-type R branch transitions from two rotameric forms. One species (extended form) has rotational constants A 0 = 9191.3(9) MHz, B 0 = 2112.61(1) MHz, C 0 = 1756.73(1) MHz which are consistent with a syn-anti (τ 1(OCOC) = 0°, r 2(cocc) = 180°) planar heavy atom structure. The second species (compact form) has rotational constants A 0 = 7760(3) MHz, B 0 = 2388.38(4) MHz, C 0 = 2102.47(3) MHz which are consistent with a syn-gauche (τ 1(ococ) = 0°, τ 2(cocc) ˜ 90°) structure. The two conformational forms have approximately equal energy (0 ± 40 cm −1). Four vibrational satellites of the extended species have been analyzed yielding a torsional frequency around the O-ethyl bond of 70(10) cm −1. Three vibrational satellites attributed to the O-ethyl torsion of the compact species have been analyzed yielding a vibrational frequency of 90(10) cm −1. Approximate Fourier coefficients of a three term potential function for internal rotation about the O-ethyl bond have been determined. Vibrational satellites attributed to the first excited states of the O-ester torsion have been analyzed for both conformers. The torsional vibrational frequency around the O-ester bond is 110(15) cm −1 for the extended conformers and 120(20) cm −1 for the compact. 相似文献
16.
A series of Ce xPr 1−xO 2−δ mixed oxides were synthesized by a sol–gel method and characterized by Raman, XRD and TPR techniques. The oxidation activity for CO, CH 3OH and CH 4 on these mixed oxides was investigated. When the value x was changed from 1.0 to 0.8, only a cubic phase CeO 2 was observed. The samples were greatly crystallized in the range of the value x from 0.99 to 0.80, which is due to the formation of solid solutions caused by the complete insertion of Pr into the CeO 2 crystal lattices. Raman bands at 465 and 1150 cm −1 in Ce xPr 1−xO 2−δ samples are attributed to the Raman active F 2g mode of CeO 2. The broad band at around 570 cm −1 in the region of 0.3 ≤ x ≤ 0.99 can be linked to oxygen vacancies. The new band at 195 cm −1 may be ascribed to the asymmetric vibration caused by the formation of oxygen vacancies. The TPR profile of Pr 6O 11 shows two reduction peaks and the reduction process is followed: . The reduction temperature of Ce xPr 1−xO 2−δ mixed oxides is lower than those of Pr 6O 11 or CeO 2. TPR results indicate that Ce xPr 1−xO 2−δ mixed oxides have higher redox properties because of the formation of Ce xPr 1−xO 2−δ solid solutions. The presence of the oxygen vacancies favors CO and CH 3OH oxidation, while the activity of CH 4 oxidation is mostly related to reduction temperatures and redox properties. 相似文献
17.
The tridecameric aluminum polymer [AlO 4Al 12(OH) 24(H 2O) 12] 7+ was prepared by forced hydrolysis of Al 3+ up to an OH/Al molar ratio of 2.2. Upon addition of sulfate, the tridecamer crystallized as the monoclinic basic aluminum sulfate Na 0.1[AlO 4Al 12(OH) 24(H 2O) 12](SO 4) 3.55. The dehydroxylation of the basic aluminum sulfate has been studied by Fourier transform in-situ infrared emission spectroscopy over a temperature range of 200° to 750°C at 50°C intervals. The spectrum is characterized by the sulfate ν1 (1024 cm −1), ν3 doublet (1117 and 1168 cm −1) and the ν4 doublet (568 and 611 cm −1) modes. Furthermore, minor bands assigned to nitrate are observed. Upon heating from ≈350° to 400°C major changes are observed, especially in the bandwidth and band intensities. The bands in the hydroxyl stretching region due to the Al 13 group disappear, whereas the bands around 1050 cm −1 display various changes in bandwidths, intensities and positions associated with the dehydration and dehydroxylation of the basic sulfate and the changing of the structure into an aluminum oxosulfate. The nitrate bands diminish upon heating. 相似文献
18.
The rotational Raman spectra of butadiene and butadiene-d 6 are found to consist of discrete lines having small ≈0·4 cm −1) yet almost constant spacings, as would be expected for symmetric or nearly symmetric top molecules. An infra-red absorption band (Type C) of butadiene at 908 cm −1 is observed to have a spacing of about 2·5 cm −1. Both the Raman and infra-red spectra provide evidence for the trans structure of the butadiene molecule. From the rotational constants A″ and
″ the following structural parameters were obtained: C=C---C) = 122·9 ± 0·5° rC---C) = 1·47 6 ± 0·010 Å dy]somewhat shorter than recently determined from electron-diffraction experiments). 相似文献
19.
139La-NMR chemical shifts were measured for several anionic complexes of formulae Li(C 4H 8O 2) 3/2 [La(ν 3-C 3H 5) 4], [Li(C 4H 8O 2) 2][Cp′ nLa(ν 3-C 3]H 5) 4−n] (Cp′ = Cp(ν 5-C 5H 5); n = 1, 2 and Cp′ = Cp * (ν 5-C 5Me5); N = 1) and Li[R nLa(ν 3-C 3H 4) 4− n] (R = N(SiMe 3) 2; n = 1, 2 and R = CCsIMe 3; n = 4), as well as for neutral compounds for formulae La(ν 3-C 3H 5) 3L n (L = (C 4H 8O 2) 1.5, (HMPT) 2, TMED), Cp′ nLa(ν 3-C 3H 5) 3−n (Cp′= Cp(ν 5-Cp 5H 5), Cp *(ν 5-C 5Me 5); n = 1, 2) and La(ν 3-C 3H 2) 2X(THF) 2 X = Cl, Br, I). Typical ranges of the 139La-NMR chemical shifts were found for the different types of complex independent of number and kind of organyl groups directly bonded to lanthanum. Zusammenfassung139La-NMR-Spektroskopie wurde an einer Reihe anionischer Allyllanthanat(III)-Komplexe der Zusammensetzung
]- [La)ν3-C3H5)4, [Li(C4H8)2][Cp′nLa(ν3-C3H5)4−n(Cp′ = Cp(ν5-C5H5); n = 1, 2 und Cp′ = Cp * (ν5-C5Me5); N = 1) und Li[RnLa(ν3-C3H5)4−n (R = B(SiMe3)2; n = 1, 2 und R = CCSiMe3; n = 4 sowie neutraler Allyllanthan(III)-Komplexe der Zusammensetzung La(ν3-C3H5)3Ln (Ln = (C4H8O2)1.5, (HMPT)2, TMED), Cp′n, La(ν3-C3H5)3−n (Cp′ = Cp(ν5-C5H5), Cp * (ν5- Cp5Me5); n = 1, 2) und La(ν3-Cp3H5)2X(THF)2 (X = Cl, Br, I) durchgefürt. In Abhängikeit von der Anzahl und der Art der am Lanthan gebundenen Gruppen wurden für die verschieden Komplextypen charakteristische Resonanzbereiche ermittelt. 相似文献
20.
The vibrational characteristics of deuterated acetonitrile dissolved in isopropanol, dimethyl formamide (DMF), and dimethyl sulfoxide (DMSO) have been studied. Observed vibrational bands show substantial frequency shifts, the amounts of which vary almost linearly with concentration. The absorption feature in the region of 2220–2280 cm −1 was deconvoluted to the consisting absorption bands. The band at 2258 cm −1 of pure CD 3CN, which is on the low frequency side of the monomer CN stretch ( ν2), is attributed to the CN stretch of the dimer (ν′ 2). The shoulder found on the further low frequency side of the ν2 band, particularly in dilute solution, is believed to be due to ν5, and its frequency and intensity vary largely as a function of concentration along with those of other vibrational bands involved with the CD 3 group. The ν5 band of pure CD 3CN is believed to be active and located at about 2251 cm −1. Ab initio calculations have also been performed for the solute–solvent complexes, CD 3CN–DMF and CD 3CN–DMSO, at the MP2/6-31+G(2d,p) level assuming anti-parallel configurations. The calculated results show a good agreement with the observed results. 相似文献
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