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There are several methods for isolating a P, Q, or R branch from the rest of the unassigned rovibrational spectrum of an asymmetric-top molecule. But at the moment, to our knowledge, once the branch has been isolated, there is no automated procedure for its assignment. Here, we present a simple semi-empirical algorithm which has proved successful in computer experiments on both S(CN)2 (a near prolate rotor) and C3H6O (a near oblate rotor.) The limits to the applicability of this method are discussed.  相似文献
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A slit nozzle continuous expansion of argon seeded with carbon dioxide is probed using a Bruker IFS 120 HR FTIR spectrometer operating at 0.05 cm−1 or 0.01 cm−1 spectral resolution. About 250 individual rovibrational transitions are assigned which belong to the asymmetric stretch of the CO2 moiety in Ar-CO2 and (CO2)2 complexes. This made it possible to refine the set of spectroscopic constants characterizing these van der Waals species. Analysis of the observed spectral features allowed for evaluation of the number densities of complexes formed in a jet. The manifold of rovibrational lines of van der Waals complexes (along with the monomer lines) sits on an unresolved pedestal, the shape of which varies dramatically as a function of reservoir pressure and initial CO2-Ar mixing ratios. Thorough examination of these variations allows for the observed features to be assigned to Arn(CO2)m clusters formed in CO2 seeded Ar expansion.  相似文献
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An analysis of the ν6=1 state of fluoroform is performed using rotational and high resolution infrared spectra. Previously radiofrequency data [Chem. Phys. Lett. 214 (1993) 265–270] and millimeter data [J. Mol. Spectrosc. 131 (1988) 1–8] were combined with new millimeter and infrared measurements, and a set of 27 parameters has been derived. A multiple fit analysis was performed confirming the assumption that the ν6=1 excited state is not affected by intervibrational resonances.  相似文献
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The high-resolution spectrum of the D2S molecule registered with a Bruker IFS 120HR Fourier spectrometer in the range 2000–4200 cm–1 is analyzed. The spectroscopic parameters of the (110), (011), and (030) vibrational states are obtained. They reproduce rotational energy levels with the accuracy close to experimental one (a total of 737 rovibrational energies is considered corresponding to 2590 transitions up to J max = 21). Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 3–7, February, 2009.  相似文献
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徐慧颖  刘勇  李仲缘  杨玉军  闫冰 《物理学报》2018,67(21):213301-213301
基于完全活性空间自洽场方法和多参考组态相互作用(multi-reference configuration interaction method,MRCI)方法,采用MRCI+Q/CBS(TQ5)+CV+SR(方法A)和aug-cc-pwCVnZ-DK(n=T,Q,5)(方法B)方案,分别计算了包含Davidson修正(+Q)、芯-价电子关联(core-valence correlation correction,CV)效应以及标量相对论(scalar relativistic,SR)效应的CO分子的基态X1+和激发态a3Π,a'3+和A1Π的势能曲线.在此基础上,获得了这些电子态的振-转谱.通过与实验结果比较发现:方法A适合a'3+和A1Π等较高激发态的振-转谱的计算,方法B更适合基态X1+和第一激发态a3Π的振-转谱的精细计算.该研究可以为其他小分子高精度振-转谱快速计算方案选择提供参考.  相似文献
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Interpreting high-resolution rovibrational spectra of weakly bound complexes commonly requires spectroscopic accuracy (<1 cm-1) potential energy surfaces (PES). Constructing high-accuracy ab initio PES relies on the high-level electronic structure approaches and the accurate physical models to represent the potentials. The coupled cluster approaches including single and double excitations with a perturbational estimate of triple excitations (CCSD(T)) have been termed the "gold standard" of electronic structure theory, and widely used in generating intermolecular interaction energies for most van der Waals complexes. However, for HCN-He complex, the observed millimeter-wave spectroscopy with high-excited resonance states has not been assigned and interpreted even on the ab initio PES computed at CCSD(T) level of theory with the complete basis set (CBS) limit. In this work, an effective three-dimensional ab initio PES for HCN-He, which explicitly incorporates dependence on the Q1 (C-H) normal-mode coordinate of the HCN monomer has been calculated at the CCSD(T)/CBS level. The post-CCSD(T) interaction energy has been examined and included in our PES. Analytic two-dimensional PESs are obtained by least-squares fitting vibrationally averaged interaction energies for v1(C-H)=0, and 1 to the Morse/Long-Range potential function form with root-mean-square deviations (RMSD) smaller than 0.011 cm-1. The role and significance of the post-CCSD(T) interaction energy contribution are clearly illustrated by comparison with the predicted rovibrational energy levels. With or without post-CCSD(T) corrections, the value of dissociation limit (D0) is 8.919 or 9.403 cm-1, respectively. The predicted millimeter-wave transitions and intensities from the PES with post-CCSD(T) excitation corrections are in good agreement with the available experimental data with RMS discrepancy of 0.072 cm-1. Moreover, the infrared spectrum for HCN-He complex is predicted for the first time. These results will serve as a good starting point and provide reliable guidance for future infrared studies of HCN doped in (He)n clusters.  相似文献
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