Vibration-rotation Analysis Research Articles

플라보노이드류의 하위 그룹을 구성하는 기본 분자들에 대한 양자 화학적 연구

A quantum study was carried out the structure and the characteristics of the basic molecules that constituting the subgroup of flavonoid i.e. flavan, flavanone, flavonol, anthocyanidine, flavone, isoflavone, and flavonol. We have reported and discussed the stable structure of isomers and physical quantities associated with the frontier energy, which are HOMO-LUMO energy difference, electronegativity, chemical potential, molecular hardness, softness, electrostatic potential, electrophilicity, electrodonating power and electro-accepting power. And we also have presented and discussed the physical quantities associated with the frontier orbital, such as frontier orbital figure, electrostatic potential diagram, polarizability, dipole moments etc., and also the values of free energy and entropy of each molecule obtained as a result of the vibration-rotation analysis The physical quantities reported and discussed are considered important data for understanding the reactivity, biological, pharmacological activity, and antioxidant properties of molecules belonging to flavonoid in the future

Formation of carnosine - an ab initio study

Formation of carnosine from histidine and b-alanine is studied by ab initio MO-LCAO-SCF method followed by the perturbative configuration interaction (MP2) in vacuo. After the full geometry optimization at the SCF level, the molecular properties were evaluated and followed by the vibrational-rotational analysis. Consequently, the energy, entropy and free energy were evaluated for the reactants and products of the reaction histidine + beta-alanine = carnosine + H2O and finally the equilibrium constant was enumerated.

Vibrational–Rotational Analysis of the Hot 2ν2–ν2 Band of the 15NH2D and 15NHD2 Molecules

High-resolution spectra of the $$2{{\nu }_{2}}{-} {{\nu }_{2}}$$ hot band of the 15NH2D and 15NHD2 molecules are investigated for the first time. The analysis is carried out based on the ground state combination difference method. As a result, the energy structure of the inversion-vibrational state ($${{{v}}_{2}}$$ = 2, s) has been obtained for each of the molecules under study and more than 480 vibrational–rotational transitions belonging to the studied hot bands have been found. Values of the upper energy levels determined based on the position of lines are used as initial data for the determination of spectroscopic parameters of the ($${{{v}}_{2}}$$ = 2, s) state.

Investigation of Micro-Raman Spectroscopy to Determine the Degree of Cure for Tiny Dot Epoxy Adhesive

Epoxy adhesive has been widely used in microelectronic production process and the technique to determine the degree of tiny dot adhesive cure is essential to evaluate the products. In this work, micro Raman spectra were demonstrated to examine the adhesive curing at small diameter of about hundred micrometers. There are two Raman peaks that can be observed then modification during the curing process while it is bond to observe the change in the infrared absorption due to the background absorption. These two Raman peaks located at 1260 and 790 cm-1 due to C-C breathing and C-O-C epoxide ring vibrating, respectively. It is found that the relative peak heights decrease as a function of UV exposure time. The vibration of Raman peak for heat cure were investigated for comparison the bond vibration of epoxy was also study by DFT in term of vibration rotation analysis for both close and open epoxy ring models which used to describe the vibration before and after curing processes. The open epoxide ring model shows the reducing of epoxide peak. Relative Raman peak heights are proposed to be used for determining the degree of adhesive cure. With imaging ability of micro Raman system, the mapping of curing sample can be illustrated by setting the color map with the proposed relative Raman peak height.

A new Nonrelativistic Investigation for Interactions in One-electron Atoms with Modified Vibrational-Rotational Analysis of Supersingular plus Quadratic Potential: Extended Quantum Mechanics

A new Nonrelativistic Investigation for Interactions in One-electron Atoms with Modified Vibrational-Rotational Analysis of Supersingular plus Quadratic Potential: Extended Quantum Mechanics

Water vapor line parameters from 6450 to 9400 cm−1

The spectra of natural water vapor were recorded in the spectral range 6450–9400cm−1 with a step-by-step Fourier transform spectrometer at room temperature with absorption path lengths up to 1200m. Positions, intensities and self-broadening coefficients of about 11,000 lines were determined. This paper focuses on the intensity parameters: the lines of four isotopologues H216O, H218O, H217O and HD16O were observed and assigned; it presents a new experimental dataset in the 6450–9400cm−1 spectral range. Obtained results were compared to the literature data. Fifty-nine new and corrected energy levels of H216O and H217O were determined from the vibration–rotation analysis of the observed lines. A brief discussion is added for self-broadening coefficients at the end of this paper.

The absorption spectrum of water in the 1.25 μm transparency window (7408–7920 cm −1)

The absorption spectrum of water vapor in “natural” isotopic abundance has been recorded between 7408 and 7920 cm −1 by high sensitivity cw-cavity ring down spectroscopy (CW-CRDS). This region covers the low energy part of the 1.25 μm transparency window and corresponds to weak water absorption of the first hexad of interacting vibrational bands. The achieved sensitivity – on the order of α min ∼ 2 × 10 −10 cm −1 – has allowed one to newly measure 2028 weak transitions with intensities down to 2 × 10 −29 cm/molecule at 296 K i.e. more than two orders of magnitude lower than previous observations. Three hundred and fourty-one new and corrected energy levels belonging to 26 vibrational states of H 2 16O, H 2 18O, H 2 17O, and HD 16O could be determined from the vibration–rotation analysis based on variational calculations by Schwenke and Partridge. The previous investigations in the studied region by Fourier Transform Spectroscopy and existing databases have been critically evaluated. The most complete list for water in the region is provided as Supplementary Material.

Vibration-rotation analysis of some nonlinear molecules by a variational method

A variational method is used to obtain vibration-rotation energies from potential functions which were derived by inverting observed band origins via perturbation theory. For the molecules SO2, NO2, CIO2, H2S, O3, H2O, D2O, and HDO we rind significant discrepancies with experiment which can be accounted for by truncation errors in the perturbation expansion.

The potential energy curve and dipole polarizability tensor of mercury dimer

Scalar relativistic coupled cluster calculations for the potential energy curve and the distance dependence of the static dipole polarizability tensor of Hg2 are presented and compared with current experimental work. The role of the basis set superposition error for the potential energy curve and the dipole polarizability is discussed in detail. Our recently optimized correlation consistent valence basis sets together with energy adjusted pseudopotentials are well suited to accurately describe the van der Waals system Hg2. The vibrational–rotational analysis of the best spin–orbit corrected potential energy curve yields re=3.74 Å, D0=328 cm−1, ωe=18.4 cm−1, and ωexe=0.28 cm−1 in reasonable agreement with experimental data (re=3.69±0.01 Å, De=380±25 cm−1, ωe=19.6±0.3 cm−1 and ωexe=0.25±0.05 cm−1). We finally present a scaled potential energy curve of the form ∑ja2jr−2j which fits the experimental fundamental vibrational transition of 19.1 cm−1 and the form of our calculated potential energy curve best (re=3.69 Å, D0=365 cm−1, ωe=19.7 cm−1, and ωexe=0.29 cm−1). We recommend these accurate two-body potentials as the starting point for the construction of many-body potentials in dynamic simulations of mercury clusters.

Vibration-rotation analysis of the jet-cooled v12, v7 + v8 and v6 + v10 absorption bands of 12C2H4

A Fourier transform interferometer was used to record the slit-jet cooled absorption spectrum of 12C2H4 between 700 and 2400 cm−1I, at a spectral resolution of 0.005 cm−1. Three bands, v12 at 1442.442 70(1)cm−1, v7 + v8 at 1888.978 23(3)cm−1 and v6 + v10 at 2047.775832(2)cm−1, were rotationally analysed. In the case of 7181, a known Coriolis perturbation mechanism involving the nearby 4181 (1958.264cm−1) and 81101 (1766.391 cm−1) states was accounted for in the analysis. The latter fitting procedure included 12 levels from the 4181 state which are observed because lines from v4 + v8 borrow intensity from v7 + v8. Compared to the literature, significantly improved vibration-rotation constants were obtained for all upper states reported in the present study.

Spectroscopic and ab initio investigation of the νOH overtone excitation in trans-formic acid

Fourier transform spectroscopy and intracavity laser absorption spectroscopy are used to record the absorption spectrum of formic acid at high spectral resolution, in the ranges of the 2νOH (6968.258 cm−1) and 4νOH (13 284.075 cm−1) vibrational bands of the trans-rotamer, respectively. Numerous perturbations combined with a large line density limit the extent to which the vibration–rotation analysis is performed. Some 689 lines are assigned in the first overtone band and related vibration–rotation constants are determined. Only the band origin and upper state principal A-rotational constant are determined for the n=4 overtone band, because of much higher spectral density. Interpolation, helped by literature data, provides all missing principal rotational constants in the nOH series, for n=1 to 4. All major vibration–rotation parameters appear to evolve very smoothly along the series. This trend is fully supported by ab initio calculations performed at the MP2/cc-pVTZ level of theory and based on an effective one-dimensional model describing the OH local mode stretching vibration. Results of these calculations are detailed in terms of the mean nuclear structure in the excitation series, up to n=4. The related calculated dipole moment surface allows the experimental a:b subband intensity ratio in the series to be interpreted in terms of a decrease in the HOC angle, from Θ≈90° (n=1) to 44°(n=4). The potential occurrence of a proton exchange mechanism between the two oxygen nuclei, close to a tautomerism mechanism, is discussed.

Vibrational—rotational dependence of molecular properties. Electric field gradients for HCl, LiCl, NaCl and KCl

The vibrational—rotational dependence of the nuclear quadrupole coupling constant (NQCC) for the isotopes 2H, 7Li, 23Na, 39K, and 35Cl is analysed in detail for the diatomic Group 1 chlorides HCl, LiCl, NaCl and KCl. The potential energy curves were calculated pointwise by using coupled cluster techniques. The electric field gradients (EFGs) and dipole moments were obtained analytically from a QCISD procedure using the Z vector method. Generally the calculated spectroscopic properties are in very good agreement with experimental data. Relativistic effects taken into account by a coupled cluster Douglas—Kroll procedure can safely be neglected for the electric field gradients up to potassium. The Inglis model which explains the trend and magnitudes of EFGs within an ionic model of weakly polarized atoms is analysed. According to this model the derivatives of the EFG, ∂ n q(R)/∂R n, with respect to the internuclear distance R should show alternating sign behaviour with increasing power n. Hence, the mechanical anharmonicity (deviation from Hooke's law potential) and the electrical anharmonicity (curvature of q(R)) are of different sign, and we expect partial cancellation of anharmonicity effects in the vibrational dependence of the NQCCs. Nevertheless, a perturbative vibrational—rotational analysis reveals a strong dependence of the chlorine and Group 1 element NQCCs on the vibrational level due to dominating mechanical anharmonicity.

Microwave Spectrum of the SD+3Ion: Molecular Structure

The J = 1–0 to 4–3 spectral lines of SD+3were measured in the 152–610 GHz region using a source-modulated microwave spectrometer. The SD+3ion was generated in a free space absorption cell by a hollow-cathode discharge in a gas mixture of D2S and D2. The rotational constant B0and the centrifugal distortion constants DJand DJKwere determined from the measured frequencies. A vibration–rotation analysis was carried out and the rzstructures of SH+3and SD+3were derived from their zero point averaged rotational constants, expressed as SH+3: rz= 1.36512(22) Å and θz= 94.098(26)°, and SD+3: rz= 1.36086(16) Å and θz= 94.1211(195)°, where the difference between θz(HSH) and θz(DSD) was assumed to be the same as that between θz(HPH) of PH3and θz(DPD) of PD3. From the shift between the rzstructures of SH+3and SD+3, the restructure of SH+3was estimated to be re= 1.35001(113) Å, θe= 94.181(135)°.

Symbolic implementation of arbitrary-order perturbation theory using computer algebra: Application to vibrational–rotational analysis of diatomic molecules

Theoretical details necessary to calculate arbitrary-order correction terms to vibrational–rotational energies and wave functions in Rayleigh–Schrödinger perturbation theory are presented. Since manual derivation of high-order perturbation formulae is not feasible due to the lengthy algebra involved, the commercial computer algebra software Mathematica® is employed to perform the symbolic manipulations necessary to derive the requisite correction formulae in terms of universal constants, molecular constants, and quantum numbers. Correction terms through sixth order for 1∑ diatomic molecules are derived and then evaluated for H 2, HD, N 2, CO, and HF. It is thus possible, with the aid of computer-generated algebra, to apply arbitrarily high-order perturbation theory successfully to the problem of intramolecular nuclear motion.

High resolution Fourier transform infrared spectrum and vibration-rotation analysis of the B-type 1584 cm − band of nitromethane

The high resolution infrared spectrum of nitromethane with a nearly free methyl internal rotor (V 6 = 2.11 cm −1) has been recorded for the B-type band near 1584 cm −1 with a Fourier transform spectrometer having a resolution of 0.005 cm −1. The ro-vibrational analysis of this dominantly NO 2 asymmetric stretching band has led to the identification of 989 transitions with 0 ≤ J ≤ 42 and 0 ≤ K α ≤ 28 for the methyl rotor m = 0 state. The transitions are fitted using Watson's A-reduction Hamiltonian in the I r representation and the least-squares fit of the assigned transitions yield the centre wavenumber and the effective rotation and centrifugal distortion constants of the upper vibrational state ( v = 1).

High-Resolution FTIR Spectrum of Jet-Cooled CH3CHF2

The mid-IR spectrum of HFC-152a, CH3CHF2, has been recorded using a supersonic jet-FTIR spectrometer system, at high and low resolution. Molecular constants have been obtained from a vibration-rotation analysis of the A-type band ν5 (1413 cm-1) and the B-type band ν16 (941 cm-1). The resultant constants have been used to simulate band profiles, from which the rotational temperature in the jet has been estimated to be 50 K. The vibrational assignment of CH3CHF2 has been revised using the low-resolution jet spectrum and Raman and far-infrared spectra recorded at room temperature.

Polyatomic surface fitting, vibrational-rotational analysis, expectation value and intensity program

A computer program, SURVIBTM, has been developed for fitting multi-dimensional potential energy and property surfaces and calculating vibrational-rotational spectra of symmetric and asymmetric top polyatomic molecules. Given surfaces in the form of internal coordinates and energy or property points, the program performs seven main types of calculations. These include determining equilibrium and saddle point geometries, internal coordinate force fields, normal mode eigensolutions, normal coordinate force fields, spectroscopic constants, expectation values of properties, and transition dipole moments and intensities. Numerous options are available for each type of calculation. High-degree expansions for several forms of analytical expressions are implemented for the representations of force fields. The vibrational analysis and transition dipole results are presented in the form of spectroscopic constants, which include anharmonicity through quartic terms according to second-order perturbation theory. Point-group symmetry is utilized for reducing the length of internal coordinate expansions and for the analysis of selection rules in calculations of vibrational absorption intensities.

Vibrational-rotational analysis of some of the fundamentals of vinylsilane

The infrared spectrum at a resolution of 0.06 cm −1 has been recorded for vinylsilane. Vibrational-rotational analysis has been carried out on ν 6, ν 13, ν 15, and the strongly coupled pair of ν 12 and ν 19. The rotational constants and some of the distortion constants have been determined for ν 6, ν 13, and ν 15, whereas higher resolution of 0.004 cm −1 was required to obtain similar data from the coupled pair of ν 12 and ν 19. These data are compared to the ground state constants previously obtained from the microwave spectrum.

Vibration-rotation analysis of C 2H 3D from 725 to 1170 cm −1

The Fourier transform spectrum of C 2H 3D has been recorded from 725 to 1170 cm −1. Higher resolution and very accurate wavenumber determination have allowed the first observation of the ν 6 vibration-rotation band, significant improvement in the knowledge of the other vibrational transitions ν 4, ν 7, ν 8, and ν 10 occurring in this spectral range, and a precise determination of the ground state rotational constants.

Vibrational-rotational analysis of ab initio potential energy surfaces for symmetric-top molecules: application to ammonia isotopomers

Author Institution: Lever Research, Inc., Edgewater; Department of Chemistry and Chemical Engineering, Stevens Institute of Technology