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51.
L. Wang V.I. Perevalov S.A. Tashkun B. Gao L.-Y. Hao 《Journal of Molecular Spectroscopy》2006,237(2):129-136
The absorption spectrum of the natural sample of nitrous oxide has been recorded at Doppler limited resolution with a Fourier-transform spectrometer in the spectral range 5000-10 000 cm−1. Ten cold bands (8Σ − Σ and 2Σ − Π), thirteen hot bands (11Π − Π, Σ − Σ, and Δ − Δ) of 14N216O and the 3ν3 band of 14N15N16O have been newly detected. The uncertainty of the line position determination is estimated to be about 0.005 cm−1 for unblended lines. The assignment of the spectrum has been done with the help of the prediction performed within the framework of the polyad model of effective Hamiltonian. The spectroscopic parameters Gv, Bv, Dv, Hv, and qv have been determined for all newly detected bands. The line intensities of 13 weak bands have been measured. The uncertainty of the obtained line intensity values varies from 7 to 13%. 相似文献
52.
Precise N2, O2, H2, Ar, He, and self-broadenings and shifts have been obtained for Q- and R-branch transitions in the ν1 fundamental band of ammonia from simultaneous fits of low-noise, high-resolution difference-frequency laser spectra at pressures from 0.07 to 27 kPa (0.5-200 Torr). Observed lineshapes exhibit significant deviations from the conventional Voigt profile, which may be attributed to Dicke narrowing and/or speed-dependent broadening. At the higher pressures, line mixing is evident and must be included in the fits. For self-broadening, line mixing is dominated by collisional tunneling transitions, whereas for the non-polar buffers, rotational relaxation among selected K states is the primary mixing mechanism. 相似文献
53.
A reinvestigation was undertaken in order to obtain reliable data of the relative intensities of the L spectra for the elements
24 ≤ Z ≤ 33. A TAP crystal with a periodicity of 25.757 ? was used as the dispersing element. With this crystal one is able
to resolve the lines/bands Ll = L3M1, Lη = L2M1, Lα1,2 = L3M4,5, Lβ1 = L2M4, and Lβ3,4 = L1M2,3. Among the investigated elements 33As is the only one for which the energy of the lines Lα1,2 and Lβ1 is below the L3 absorption edge. For all the other elements the lines Ll, Lη, and Lα1,2 are below the L3 edge, whereas Lβ1 and Lβ3,4 are above this edge. This difference leads to effects of differential absorption, where the absorption is stronger for decreasing
line energy. For the net peak height ratio β1/α we obtained results which are of the same order of magnitude as those given by White and Johnson (W&J) in their popular
tables. But for l/α and β3,4/β1 our results show an atomic number dependence which is completely different from those given by W&J. 相似文献
54.
The accuracies of the calculated vibrational frequencies and Raman intensities given by two new, highly compact Pol-type basis sets, Z2PolX and Z3PolX, have been determined and compared to the 6-31G(d), PolX, and aug-cc-pVTZ basis sets. Calculation of accurate Raman intensities has previously required large basis sets, but the ZmPolX basis sets are smaller even than PolX, which are the most compact basis sets able to calculate accurate Raman intensities. For the largest compound studied, C5H10O2, Z3PolX required more than an order of magnitude less CPU time than PolX, which has been shown to be 10 times faster than aug-cc-pVTZ. Two sets of test molecules were studied: one was a series of small molecules for which experimental values for absolute Raman activities were available; the second was a series of medium-sized molecules (mainly common organic solvents) where only relative Raman band intensities were available. The accuracies of the Raman intensities given by both of the ZmPolX basis sets were good compared to those of the PolX and aug-cc-pVTZ sets, and much better than the 6-31G(d) values. The errors in even unscaled frequency values <2000 cm(-1) were also acceptable and were slightly lower for Z3PolX than Z2PolX (30 cm(-1) vs. 48 cm(-1)). The combination of good intensity and frequency data meant that for the medium-sized organic molecules there was a close correspondence between the simulated Raman spectra and experimental data, and that the observed bands could easily be assigned on the basis of these calculations. Achieving this level of accuracy in the simulations at modest computational cost should now allow computational methods to be combined with experimental Raman studies much more widely than is currently the case. 相似文献
55.
C. J. Powell 《Surface and interface analysis : SIA》2007,39(5):464-466
This article is a brief summary of the ISO Standard 20903. This standard provides information on methods for the measurement of peak intensities in Auger electron and X‐ray photoelectron spectra and on uncertainties of the derived peak areas. It also specifies the necessary information required in a report of analytical results based on such measurements. Published in 2007 by John Wiley & Sons, Ltd. 相似文献
56.
Summary A reexamination of the vibrational coordinates appropriate in vibronic intensity calculations in octahedral coordination compounds is presented. We derive a complete set of symmetry coordinates that is orthonormal and transforms correctly under the group generators. The vibronic hamiltonian for the crystal field and ligand polarization contributions to the intensity are calculated in the basis of these coordinates. The crystal field term is evaluated both using a truncated basis set for the intermediate electronic states and using the closure approximation. These methods have been applied to the calculation of the vibronic intensity distribution for the4
A
2g
2
E
g transition of the MnF
6
2–
ion and close agreement wtih experiment achieved. 相似文献
57.
We report a six-dimensional CCSD(T)/aug-cc-pVTZ dipole moment surface for the electronic ground state of PH3 computed ab initio on a large grid of 10 080 molecular geometries. Parameterized, analytical functions are fitted through the ab initio data, and the resulting dipole moment functions are used, together with a potential energy function determined by refining an existing ab initio surface in fittings to experimental wavenumber data, for simulating absorption spectra of the first three polyads of PH3, i.e., (ν2, ν4), (ν1, ν3, 2ν2, 2ν4, ν2 + ν4), and (ν1 + ν2, ν3 + ν2, ν1 + ν4, ν3 + ν4, 2ν2 + ν4, ν2 + 2ν4, 3ν2, 3ν4). The resulting theoretical transition moments show excellent agreement with experiment. A line-by-line comparison of the simulated intensities of the ν2/ν4 band system with 955 experimental intensity values reported by Brown et al. [L.R. Brown, R.L. Sams, I. Kleiner, C. Cottaz, L. Sagui, J. Mol. Spectrosc. 215 (2002) 178-203] gives an average absolute percentage deviation of 8.7% (and a root-mean-square deviation of 0.94 cm−1 for the transition wavenumbers). This is very remarkable since the calculations rely entirely on ab initio dipole moment surfaces and do not involve any adjustment of these surfaces to reproduce the experimental intensities. Finally, we predict the line strengths for transitions between so-called cluster levels (near-degenerate levels formed at high rotational excitation) for J up to 60. 相似文献
58.
Natieli Alves da Silva Luiz Alberto Terrabuio Roberto Luiz Andrade Haiduke 《International journal of quantum chemistry》2017,117(3):197-207
This investigation uses atomic properties derived from the quantum theory of atoms in molecules formalism to rationalize the infrared intensity of the stretching vibration that arises as a Lewis base (B) is protonated (B‐H mode). Moreover, the interacting quantum atom (IQA) partition is employed to evaluate the energetics of protonation. All calculations are performed at the CCSD/cc‐pVQZ level except by the IQA analysis, which is carried out by means of the B3LYP/cc‐pVQZ//CCSD/cc‐pVQZ treatment. First, an efficiency scale is established for Lewis bases in terms of the electronic charge transfer potential. Next, this study shows that the intensity of the B‐H stretching depends mostly on the electronic charge amount transferred to the proton. Thus, intensity data provide empirical assessment of Lewis base charge transfer efficiency. Finally, the group separation observed during correlation of proton affinities and electronic charge transfer potential is explained by the interaction energy between fragments of the protonated system. 相似文献
59.
60.
RKR turning points for the B(1∑+) and X(1∑+) states of DF have been calculated. Franck-Condon factors and r-centroids for the B-X band system of HF and DF have been evlauated and compared with previous experimental results. 相似文献