Vibrational modes of the stibine molecule

In this paper, we use the algebraic approach to describe the vibrational modes of stibine molecule (of C_3v molecular symmetry group) up to 21 quanta. As the stibine molecule exhibits stretch-bend resonances, we build an algebraic pyramidal coupling operator between stretching modes and bending modes adapted to this molecule. The standard deviation associated to the fit of the vibrational levels is 1.75 cm⁻¹.     

Dispersed fluorescence spectroscopy of S0 vibrational levels in formaldehyde-d

High resolution dispersed fluorescence (DF) spectra of excited vibrational levels in S₀ HDCO up to 10 000 cm⁻¹ energy were recorded in a free-jet expansion. Excitation to the 0₀₀ rotational level in 4⁰ and 4¹ S₁ HDCO yielded pure vibrational spectra that are free from rotational congestion. The 162 transitions (133 unique vibrational levels) assigned in these spectra have been fit to a multiresonant Hamiltonian model, which includes harmonic frequencies , anharmonic constants (x_ij), and resonance constants (K). The assigned vibrational states were fit to the model with a standard deviation of 4.02 cm⁻¹. Extensive vibrational mixing is observed throughout the spectra. Six harmonic constants, eight anharmonic constants, and four resonance constants (K_44,1, K_66,1, K_44,66, and K_33,5) were determined experimentally. The 18 experimentally determined spectroscopic constants, with the exception of and K_66,1, were found to agree within 6 cm⁻¹ of ab initio calculated values.     

Li_2部分电子态的完全振动能谱与离解能的精确研究

本文将孙卫国等建立的精确计算双原子分子离解能的解析表达式作为分子振动能级正确收敛的重要物理判据,应用代数方法,进一步研究了重要的碱金属Li2的5个电子态的完全振动能谱和离解能,获得了这些电子态的精确振动光谱常数,同时也得到了包括接近分子离解极限在内的完全振动能谱和与实验值符合得很好的理论离解能.这些计算结果为许多需要这些电子态振动数据的研究领域提供了重要的研究数据.     

Rotational energy surface and quasiclassical analysis of the rotational energy level cluster formation in the ground vibrational state of PH3

We report and substantiate a method for constructing the rotational energy surface (RES) of a molecule as a pure classical object. For an arbitrary molecule we start from the potential energy surface rather than from a conventional “effective Hamiltonian”. The method is used for constructing the RES of the PH₃ molecule in its ground vibrational state. We have used an ab initio potential energy surface [D. Wang, Q. Shi, Q.-S. Zhu, J. Chem. Phys. 112 (2000) 9624-9631; S.N. Yurchenko, M. Carvajal, P. Jensen, F. Herregodts, T.R. Huet, Chem. Phys. 290 (2003) 59-67.]. The shape of the RES is shown not to change for J from 0 to 120. The procedure of quasiclassical quantization of the RES was also undertaken, yielding a set of quasiclassical critical values of the angular momentum. The results explain the structure of quantum rotational energy levels obtained by variational calculations [S.N. Yurchenko, W. Thiel, S. Patchkovskii, P. Jensen, Phys. Chem. Chem. Phys. 7 (2005) 573-582].     

Theoretical study of the new compound VO2 (D)

The structural feature and the electronic properties of the newly synthesized compound VO₂ (D) are theoretically studied. Our calculations reveal that all of the V ions in VO₂ (D) form two types of chains. One of the chains contributes to the electronic states near the Fermi level, but the other one almost does not yet. Such discrepancy is attributed to the different strength of the VO bonds belonging to the different chains. Furthermore, it is found that one type of the VV chains characters the antiferromagnetic feature, whereas the other one is almost non-magnetic. So, the compound VO₂ (D) is of one-dimensional antiferromagnetic ordering. In addition, we propose that the structural transition from VO₂ (D) to the rutile-type VO₂ (R) is driven by three vibrational modes. The transition temperature is estimated to be about 600 K, being consistent with experiment.     

Electronic energy levels of CsCdCl3

The excitation and emission spectra of CsCdCl₃ crystal grown by the Bridgman growth technique, are observed. Its dominant excitation spectra correspond to the transitions between the electronic energy levels of the face-shared [CdCl₆]⁴⁻ octahedron complexes with C_3v symmetry. With the help of the molecular orbital diagram of the [CdCl₆]⁴⁻ molecule complex, an approximate electronic energy level diagram of this crystal is constructed using one-electron approximation.     

Determination of vibrational energy levels and transition dipole moments of CO2 molecules by density functional theory

An efficient method is presented to calculate the intra-molecular potential energies and electrical dipole moments of CO₂ molecules at the electronic ground state by solving the Kohn-Sham (KS) equation for a total of 101 992 nuclear configurations. The projector-augmented wave (PAW) exchange-correlation potential functionals and plane wave (PW) basis functions were used in solving the KS equation. The calculated intra-molecular potential function was then included in the pure vibrational Schrödinger equation to determine the vibrational energy eigen values and eigen functions. The vibrational wave functions combined with the calculated dipole moment function were used to determine the transition dipole moments. The calculated results were compared with the experimental data.     

Vibrational Spectroscopic Studies of Molybdena Dispersed on Ceria Support

Abstract

Diffuse Reflectance Infrared Fourier Transform (DRIFT) and FT-Raman spectra have been used to investigate the interactions between molybdena and ceria in MoO₃/CeO₂ samples with different Mo loadings. The spectra exhibit a weak Mo=O broad band of surface species at ca. 920–970 cm^?1, which reveals that the interaction between dispersed molybdena and ceria could be mainly ionic in nature. With the increasing of Mo loadings, the observed Mo=O band broadening and frequency shifting are due to the overlapping and condensation of different hydrated surface species. On the basis of the measured surface dispersion capacity of morybdena and the structure of the preferentially exposed (111) plane of ceria, it is reasonable to suggest that the Mo⁶⁺ cations and the accompanying O²- anions are incorporated into the surface available vacant sites of CeO₂, accordingly the dispersed molybdena species are interacted electrostatically with the support instead of only physically dispersed on the surface of it.     

On the origin of the 2.2-2.3 eV photoluminescence from chemically etched germanium

The photoluminescence (PL) at ∼2.2-2.3 eV from Ge-based nanocrystalline materials is described in the literature as nanocrystal size-independent. We have observed visible luminescence from two different types of stain-etched Ge samples, one prepared after Sendova-Vassileva et al. (Thin Solid Films 255 (1995) 282) in a solution of H₂O₂:HF at 50:1 volume ratio, and the other in a solution of HF:H₃PO₄:H₂O₂ at 34:17:1 volume ratio. Energy dispersive X-ray analysis (EDX), Raman and FTIR spectroscopy, and the near edge X-ray absorption structure (XANES), indicate that the chemically etched Ge layers of the former type of samples are composed of non-stoichometric Ge oxides, i.e. GeO_x (0<x<2), and free from any Ge nanoconstructions. It is also suggested from XANES that the latter type of chemically etched Ge samples comprise 8-9 nm nanocrystals of Ge, surface-covered with mainly oxygen. Photoluminescence occurred at ∼2.3 eV for all samples. The PL behavior of the latter type of chemically etched Ge on annealing in different chemical environments (air or H) allowed us to conclude that the PL from these materials, as well as that from those Ge-based nanocrystalline materials reported in the literature, is from GeO_xs.     

Theoretical study of structure and analytic potential energy function for the ground state of PO2 molecule

In this paper, the energy, the equilibrium geometry, and the harmonic frequency of the ground electronic state of PO₂ are computed using B3LYP, B3P86, CCSD(T), and QCISD(T) methods in conjunction with 6-311++G(3df, 3pd) and cc-pVTZ basis sets. A comparison between the computational results and the experimental values indicates that the B3P86/6-311++G(3df, 3pd) method can give better energy calculation results for the PO₂ molecule. It is shown that the ground state of the PO₂ molecule has C_2v symmetry and its ground electronic state is X²A₁. The equilibrium parameters of the structure are R_P-O=0.1465 nm, d=19.218 eV. The bent vibrational frequency ν₁=386 cm^-1, the symmetric stretching frequency ν₂=1095 cm^-1, and the asymmetric stretching frequency ν₃=1333 cm^-1 are obtained. On the basis of atomic and molecular reaction statics, the reasonable dissociation limit for the ground state of the PO₂ molecule is determined. Then the analytic potential energy function of the PO₂ molecule is first derived by using the many-body expansion theory. The potential curves correctly reproduce the configurations and the dissociation energy for the PO₂ molecule.     

Rotational analysis of bands in the high-resolution infrared spectra of the three species of butadiene-1,4-d2; refinement of the assignments of the vibrational fundamentals

Samples of trans,trans and cis,cis forms of butadiene-1,4-d₂ have been synthesized and found to contain useful amounts of the cis,trans species as a contaminant. Assignments of fundamental frequencies for the three isotopomers of butadiene-1,4-d₂ have been extended and improved from investigations of their Raman spectra as well as their infrared (IR) spectra. High-resolution IR spectra have been recorded for the three isotopomers, and a rotational analysis has been completed for strong bands of each species. Ground state and some upper state rotational constants have been fit. Corresponding ground state moments of inertia compare favorably with equilibrium moments of inertia obtained from B3LYP/6-311++G** theory. Two ¹³C isotopomers are being prepared, and an improved structural analysis of butadiene will soon be available to assess how π-electron delocalization affects its structure.     

CW-cavity ring down spectroscopy of the ozone molecule in the 6625-6830 cm region

The absorption spectrum of ozone, ¹⁶O₃, has been recorded by CW-cavity ring down spectroscopy in the 6625-6830 cm⁻¹ region. The typical sensitivity of these recordings (α_min ∼ 3 × 10⁻¹⁰ cm⁻¹) allows observing very weak transitions with intensity down to 2 × 10⁻²⁸ cm/molecule. 483 and 299 transitions have been assigned to the 2ν₁ + 3ν₂ + 3ν₃A-type band and to the 2ν₁ + 4ν₂ + 2ν₃B-type band, respectively, which are the highest frequency bands of ozone recorded so far under high resolution. Rovibrational transitions with J and K_a values up to 46 and 12, respectively, could be assigned. Despite well-known difficulties to correctly reproduce the energy levels not far from the dissociation limit, it was possible to determine the parameters of an effective Hamiltonian which includes six vibrational states, four of them being dark states. The line positions analysis led to an rms deviation of 8.5 × 10⁻³ cm⁻¹ while the experimental line intensities could be satisfactorily reproduced. Additional experiments in the 5970-6021 cm⁻¹ region allows detecting the (233) ← (010) hot band reaching the same upper state as the preceding cold band. From the effective parameters of the (233) state just determined and those of the (010) level available in the literature, 329 transitions could be assigned and used for a further refinement of the rovibrational parameters of the effective Hamiltonian leading to a value of 7.6 × 10⁻³ cm⁻¹ for the global rms deviation. The complete list of the experimentally determined rovibrational energy levels of the (233), (242), and (520) states is given. The determined effective Hamiltonian and transition moment operators allowed calculating a line list (intensity cut off of 10⁻²⁸ cm/molecule at 296 K), available as Supplementary material for the 6590-6860 and 5916-6021 cm⁻¹ regions. The integrated band strength values are 1.75 × 10⁻²⁴ and 4.78 × 10⁻²⁵ cm/molecule at 296 K for the 2ν₁ + 3ν₂ + 3ν₃A-type band and to the 2ν₁ + 4ν₂ + 2ν₃B-type band, respectively, while the band intensity value of the (233) ← (010) is estimated to be 1.03 × 10⁻²⁴ cm/molecule.     

The bending triad of the quasi-spherical top molecule SO2F2 in the 550 cm region

The analysis of the ν₃/ν₇/ν₉ bending triad of SO₂F₂ has been recently performed with the Watson’s Hamiltonian up to octic terms employing 79 rovibrational parameters but including only the first order Coriolis interaction terms, fixed to ab initio values [H. Bürger, J. Demaison, F. Hegelund, L. Margulès, I. Merke, J. Mol. Struct. 612 (2002) 133-141]. Since SO₂F₂ is a quasi-spherical top, it can also be considered as derived from the sulfate ion. We have thus developed a new tensorial formalism in the O (3) ⊃ T_d ⊃ C_2v group chain [M. Rotger, V. Boudon, M. Loëte, J. Mol. Spectrosc. 216 (2002) 297-307]. This approach allows a systematic development of rovibrational interactions and makes global analyses easier to perform even for complex polyad systems. We present here an application of this model to the analysis of the bending triad, with the same set of microwave assignments and almost the same set of infrared assignments as in the previous study of Bürger et al. It appears that we need to expand our Hamiltonian to a lower degree than the “classical” one (six instead of eight) when including also the second order Coriolis interactions. Our fit does not include more parameters. Furthermore, all of them are determined and the standard deviation of the rotational transitions is twice smaller. The analysis has been performed thanks to the C_2v TDS program suite, which is freely available at the URL: http://www.u-bourgogne.fr/LPUB/c2vTDS.html.